,,outlines  ,,of  ,,dairy ,,bacteriology
  ,a ,,concise ,,manual ,,for ,,the     
,,use ,,of ,,students ,,in ,,dairying   
,,by  ,h4 ,l4 ,,russell  ,dean of the   
,college of ,agriculture ,university of 
,wisconsin  ,,and  ,e4 ,g4 ,,hastings   
,professor of ,agricultural             
,bacteriology ,university of ,wisconsin 
,,tenth ,,edition  ,,madison1           
,,wisconsin ,h4 ,l4 ,,russell #aiad     
,copyright #aiad  ,,by  ,h4 ,l4         
,,russell ,,and ,e4 ,g4 ,,hastings      
,,preface ,,to ,,the ,,tenth ,,edition4 
,this text was originally the outgrowth 
of a series of lectures on the subject  
of dairy bacteriology to practical      
students in the winter ,dairy ,course in
 the ,university of ,wisconsin4 ,the    
importance of bacteriology in dairy     
processes has now come to be so widely  
recognized that no student of dairying  
regards his training as complete until  
he has had the fundamental principles of
 this subject4  ,the aim of this volume 
is not to furnish an exhaustive treatise

 of the subject1 but an outline and     
sufficient detail to enable the general 
student of dairying to obtain as        
comprehensive an idea of the bacteria   
and their effects on milk and other     
dairy products as may be possible       
without the aid of laboratory practice4 
,when possible the dairy student is     
urged to secure a laboratory knowledge  
of these organisms1 but lacking this1   
the student and general reader should   
secure a general survey of the field of 
bacteriology in relation to dairying4   
,in this1 the tenth edition1 the effort 
has been made to include all of the     
recent developments of the subject4     
,especially is this true in regard to   
the subject of market milk1 a phase of  
dairying that has gained greatly in     
importance in the last few years4 ,the  
changes in the methods of handling      
market milk have been marked4 ,the      
results of these changes in influencing 
the quality of milk offered to the      
consumer are fully discussed4   ,h4 ,l4 

,r4  ,e4 ,g4 ,h4     ,,contents         
,structure1 ,growth and ,distribution of
 ,bacteria                      #g      
,methods of ,studying ,bacteria         
#bj  ,contamination of ,milk            
#bh  ,infection of ,milk with           
,pathogenic ,bacteria                   
#fb  ,fermentations of ,milk            
#hb  ,preservation of ,milk             
#aac  ,bacteria and ,butter ,making     
#acf  ,bacteria and ,cheese ,making     
#afa  ,bacteria in ,market ,milk        
#ahi     ,,chapter ,i4  ,,structure1    
,,growth ,,and ,,distribution4          
,relation of bacteriology to dairying4  
,the arts which have been developed by  
mankind have been the outgrowth of      
experience4 ,man first learned by doing1
 how to perform these various           
activities1 and a scientific knowledge  
of the underlying principles which      
govern these processes was later        
developed4  ,the art of dairying has    
been practiced from time immemorial1 but
 a correct understanding of the         

fundamental principles on which the     
practice of dairying rests is of recent 
origin4 ,in working out these           
principles1 chemistry has been of great 
service1 but in later years1            
bacteriology has also been most         
successfully applied to the problems of 
modern dairying4 ,indeed1 it may be said
 that the science of dairying1 as       
related to the problems of dairy        
manufacture is1 in large degree1        
dependent upon an understanding of      
bacteriological principles4 ,it is      
therefore essential that the student of 
dairying1 even though he is concerned in
 large measure with the practical       
aspects of the subject1 should acquire  
as complete an understanding of these   
principles as possible4  ,while         
bacteriology is concerned primarily with
 the activities of those microscopic    
forms of plant life known as the        
bacteria1 yet the general principles    
governing the life of this particular   
class of organisms are sufficiently     

similar to those governing the molds and
 other types of microscopic life that   
affect milk and its products to make it 
possible to include all of these types  
in a general consideration of the       
subject4  ,nature of bacteria4 ,the     
vegetable kingdom to which the bacteria 
belong consists of plants of the most   
varying size and nature4 ,those of most 
common acquaintance are the green plants
 varying in size from those not visible 
to the naked eye to the largest trees4  
,another class of plants known as fungi 
or fungous plants do not contain        
chlorophyll1 the green coloring matter1 
but are usually colorless and1 as a     
rule1 of small size2 among them are     
included such forms as the mushrooms1   
smuts1 rusts and mildews1 as well as the
 molds and yeasts4 ,the bacteria are    
closely allied to this latter class4    
,when first discovered they were thought
 to be animals because of the ability of
 some forms to move about in liquids4   
,the bacteria1 like other kinds of      

living organisms1 possess a definite    
form and shape4 ,they are the simplest  
in structure of all the plants1 the     
individual organism consisting of a     
single cell4 ,the larger and more highly
 organized forms of life are made up of 
many microscopic cells1 and the life of 
the individual consists of the work of  
all the cells4 ,the bacteria are very   
comparable to the single cells of the   
higher plants and animals1 but in the   
case of the bacteria the single cell is 
able to exist apart from all other cells
 and to carry out all of its life       
processes including reproduction4       
,forms of bacteria4 ,with the           
multicellular organisms much variation  
in form is possible1 but with these     
single-celled organisms the possible    
variation in form is greatly limited4   
,three well marked types occur among the
 bacteria3 the round or coccus form     
7plural cocci72 the rod-shaped or       
bacillus 7plural bacilli72 and the      
twisted or spirillum type 7plural       

spirilla74 ,most organisms of special   
significance in dairying belong to the  
coccus or bacillus group4  ,size of     
bacteria4 ,the bacteria1 as a class1 are
 among the smallest of living objects4  
,none of them are individually visible  
to the naked eye1 and they can be so    
seen only when clumps or masses are     
formed in the process of growth4        
,illustration3 ,fig4 #a4--;,forms of    
,bacteria4 ,a1 coccus2 ,b1 bacillus2 ,c1
 spirillum4  ,while there is            
considerable relative variation in size1
 yet in actual dimensions1 this         
difference is so small as to make       
careful microscopic determinations      
necessary4 ,an average diameter may be  
taken as about one thirty-thousandth of 
an inch1 while the length varies        
naturally several fold1 depending upon  
whether the type under observation is a 
coccus or a bacillus4  ,it is very      
difficult to conceive of the minuteness 
of the bacteria2 the following may give 
some idea of their size4 ,in a drop of  

cream ready for churning may be found as
 many as #aj1jjj1jjj and in a piece of  
fresh cheese as large as a cherry there 
may be as many living bacteria as there 
are people on our earth4 ,while the     
bacteria are very minute1 the effect    
which they exert in milk and other dairy
 products is great on account of their  
enormous numbers4  ,manner of growth4   
,the cells of which all plants and      
animals consist increase in numbers by  
the division of each cell into two cells
 through the formation of a division    
wall across the cell4 ,the new cells    
divide and the plant or animal continues
 to grow4 ,the same cell division occurs
 in the bacteria but since the bacteria 
are single celled1 division of the cells
 means an increase in numbers rather    
than growth as in the higher forms of   
life4  ,illustration3 ,fig4             
#b4--;,division of ,bacteria4  ,the     
bacteria increase in numbers by the     
division of each cell into two cells4   
7,after ,novy47  ,in the case of those  

bacteria that have a greater length than
 diameter1 the new wall is formed at    
right angles to the long axis of the    
cell4 ,as soon as the division is       
complete each cell is a complete        
individual1 capable of carrying on all  
of its life processes4 ,the cells may1  
however1 cohere and thus form           
distinctive groupings that may serve to 
identify certain types4 ,some of the    
cocci form long chains and the term     
streptococcus is applied to such4 ,other
 groupings may be similar to a bale of  
twine or they may be massed in clusters 
with no regularity distinguishable4     
,spores4 ,just as ordinary plants form  
resistant structures1 known as seeds1   
capable of retaining vitality under     
conditions unfavorable for growth       
thereby perpetuating the species1 so    
with certain of the bacteria1 definite  
structures1 known as spores1 that are   
analogous in some respects to the seeds 
of the higher plants1 are produced      
within the mother cell4 ,the spores are 

exceedingly resistant to the influence  
of an unfavorable environment1 such as  
heat1 cold1 drying1 and even chemical   
agents4 ,it is this property of the     
spores which makes it so difficult to   
destroy the bacterial life in the       
process of sterilizing milk4 ,the       
property of spore-formation is          
fortunately confined to a comparatively 
small number of different species of    
bacilli4  ,movement4 ,many of the       
bacteria are provided with vibratory    
organs of locomotion1 known as cilia    
7singular cilium7 which are variously   
distributed on the surface of the cell4 
,by the movement of these relatively    
long1 thread-like appendages the        
individual cell is able to move in      
liquids4 ,it must be remembered1 when   
these moving cells are observed under   
the microscope1 that their apparent rate
 of movement is magnified relatively as 
much as their size4  ,conditions for    
growth4 ,all kinds of living things need
 certain conditions for growth such as  

food1 moisture1 air and a favorable     
temperature4 ,the bacteria prefer as    
food such organic matter as milk1 meat1 
and vegetable infusions4 ,those living  
on dead organic matter are known as     
saprophytes1 while those which are      
capable of thriving in the tissues of   
the living plant or animal are known as 
parasites4 ,certain of the parasitic    
forms are capable of causing disease in 
plants and animals4 ,in the first group 
are embraced most of the bacteria that  
are able to develop in milk or its      
products1 such as those forms concerned 
in the spoiling of milk or its          
fermentation4 ,it is true that milk may 
contain disease-producing bacteria      
coming either from a diseased animal or 
from a diseased human being4 ,it is also
 true that some of such harmful forms   
are able to grow in milk1 such as the   
organisms causing typhoid fever and     
diphtheria4  ,food4 ,the bacteria like  
all other plants must have their food in
 solution4 ,where they apparently live  

on solids1 such as meats1 fruits1 etc41 
they dissolve the food substances before
 utilizing the same4 ,if the solutions  
are highly concentrated1 as in the case 
of syrups1 preserves and condensed milk1
 the bacteria cannot readily grow1      
although all of the necessary food      
ingredients are present4 ,when such     
concentrated solutions are diluted1     
bacterial growth will take place and the
 solutions will spoil4  ,illustration3  
,fig4 #c4--,photomicrograph of ,lactic  
,acid ,bacteria4  ,each cell is an      
individual organism1 magnified #abej    
diameters4  ,generally speaking the     
bacteria grow best in a neutral or      
slightly alkaline solution rather than  
in acid liquids4  ,temperature4 ,one of 
the most important conditions           
influencing the rate of growth of       
bacteria is the temperature4 ,each form 
has a minimum temperature below which   
growth can not take place2 also a       
maximum above which growth is again     
impossible4 ,for the majority of species

 the minimum temperature ranges from #dj
 to #de ,f4 the maximum from #aje to    
#aaj ,f4 ,growth takes place most       
rapidly at the optimum temperature1     
which1 for each species1 lies close to  
the maximum temperature at which growth 
can occur4 ,most of the bacteria of     
importance in the dairy grow well at    
from #gj to #ajj ,f4  ,there are forms  
that can grow below the freezing point  
of water when they are in solutions that
 do not freeze at this temperature4     
,there are still other bacteria that can
 grow at #adj ,f4 a temperature that is 
quickly fatal to most forms4 ,these are 
of importance in the dairy since they   
limit the temperatures at which milk can
 be stored for long periods of time4    
,air supply4 ,living organisms1 both    
plant and animal1 require air or oxygen 
for the combustion of their food and for
 the production of energy4 ,most        
bacteria use1 as do the green plants and
 animals1 the free oxygen of the air for
 their respiration4 ,such organisms are 

called aerobic or air-living4 ,a much   
smaller group possess the power of      
taking oxygen from organic compounds    
such as sugar and the like and therefore
 are able to live under conditions where
 air is excluded4 ,these are called     
anaerobic bacteria4 ,a large number of  
bacteria are able to live either in the 
presence or in the absence of free      
oxygen4 ,most of the bacteria of        
importance in the dairy are of this     
nature4  ,rate of growth4 ,when there is
 an abundant supply of food and when the
 temperature conditions are favorable1  
the bacteria increase in numbers with   
astounding rapidity4 ,it has been       
determined by actual experiment that the
 process of cell division under         
favorable conditions takes place in a   
few moments4 ,barber has shown that one 
of the forms of bacteria constantly     
found in milk will divide in #ag minutes
 at #ih ,f4 and that a single organism  
kept at this temperature for ten hours  
would increase to #a1bdj1jjj1jjj4 ,if   

the temperature is reduced to #ej ,f41  
the time required for division is       
increased to several hours4 ,the        
explanation for the rapid spoiling of   
milk that is not well cooled is thus    
apparent4 ,the initial rapid rate of    
increase cannot be maintained for any   
length of time as the conditions become 
more and more unfavorable as growth     
continues1 due to the accumulation of   
the by-products of the cell activity4   
,thus1 the growth of acid-forming       
organisms in milk becomes checked by the
 formation of acid from the fermentation
 of the sugar4  ,detrimental effect of  
external conditions4 ,environmental     
conditions of a detrimental character   
are constantly at work tending to       
repress the activity of bacteria or to  
destroy them4 ,these act more readily on
 the vegetating cells than on the more  
resistant spores4 ,it is of the utmost  
importance that those engaged in dairy  
work be familiar with these antagonistic
 forces since it is constantly necessary

 to repress or to kill outright the     
bacteria in milk and other dairy        
products4 ,in many lines of dairy work  
it is likewise important to be familiar 
with the conditions favorable for       
bacterial growth4  ,effect of cold4     
,while it is true that chilling largely 
prevents fermentative action1 and actual
 freezing stops all growth processes1   
still it does not follow that exposure  
to low temperatures will effectually    
destroy the vitality of bacteria1 even  
in the growing condition4 ,numerous     
non-spore-bearing species remain alive  
in ice for a prolonged period1 and      
experiments with liquid air show that   
even a temperature of-#caj ,f4          
maintained for hours does not kill all  
exposed cells4  ,effect of heat4 ,high  
temperatures1 on the other hand1 will   
destroy any form of life1 whether in the
 vegetative or latent spore stage4 ,the 
temperature at which the vitality of the
 cell is lost is known as the thermal   
death point4 ,this limit is dependent   

not only upon the nature of the         
organism1 but upon the time of exposure 
and the condition in which the heat is  
applied4 ,in a moist atmosphere1 the    
penetrating power of heat is great1     
consequently cell death occurs at a     
lower temperature than in a dry         
atmosphere4 ,an increase in time of     
exposure lowers the temperature point at
 which death occurs4  ,for growing      
organisms1 the thermal death point of   
most species ranges from #acj to #adj   
,f4 for ten minutes4 ,when spores are   
present1 resistance is greatly          
increased1 some forms being able to     
withstand steam at #bab ,f4 from one to 
three hours4 ,in the sterilization of   
milk1 it is often necessary to heat for 
several hours1 where a single exposure  
is made1 to destroy the resistant       
spores1 that seem to be more abundant   
under summer than winter conditions4    
,steam under pressure is a much more    
effective agent1 as the temperature is  
thus raised considerably beyond #bab ,f4

 ,an exposure of twenty minutes1 at a   
temperature of #bcj to #bdj ,f4 will    
kill all spores4 ,where heat is used in 
a dry state1 it is much less effective1 
a baking temperature of #bfj to #cjj ,f4
 for an hour being necessary to kill    
spores4 ,this condition is of the utmost
 importance in the destruction of       
bacteria in the dairy and creamery4     
,effect of drying4 ,the spore-bearing   
bacteria withstand effects of           
desiccation without serious injury1 and 
many of the non-spore-producing types   
retain their vitality for some months4  
,the bacteria found in the air are      
practically all derived from the soil1  
and exist in the air in a dried         
condition1 in which they are able to    
remain alive for considerable periods of
 time4 ,in a dried condition1 active    
cell growth is not possible1 but when   
other conditions1 such as moisture and  
food supply are present1 resumption of  
growth quickly begins4 ,this property is
 also of importance in the dairy as in  

the preparation of dry starters for     
creameries and cheese factories4        
,effect of light4 ,bright sunlight      
exerts a markedly injurious effect on   
bacterial life1 both in a spore and in a
 growing condition4 ,where the direct   
sunlight strikes1 more or less complete 
disinfection results in the course of a 
few hours1 the effect being produced by 
the chemical or violet rays1 and not by 
the heat or red rays of the spectrum4   
,this action1 however1 does not         
penetrate opaque objects1 and is        
therefore confined to the surface4 ,in  
diffused light1 the effect is much      
lessened1 although it is exerted to some
 extent4 ,sunlight exerts a beneficial  
effect on the general health and        
well-being of animal life1 and is a     
matter of importance to be taken into   
consideration in the erection of        
buildings for animals as well as for    
people4  ,effect of chemicals4 ,a great 
many chemical substances exert a more or
 less powerful toxic action on various  

kinds of life4 ,many of these are of    
great service in destroying bacteria or 
holding them in check4 ,those that are  
toxic and result in the death of the    
cell are known as disinfectants2 those  
that merely inhibit1 or retard growth   
are known as antiseptics4 ,all          
disinfectants must of necessity be      
antiseptic in their action1 but not all 
antiseptics are disinfectants1 even when
 used in large amounts4 ,disinfectants  
have no place in dairy work1 except to  
destroy disease-producing bacteria1 or  
to preserve milk for analytical         
purposes4 ,the so-called chemical       
preservatives used to keep milk depend  
for their effect on the inhibition of   
bacterial growth4 ,in this country1 most
 states prohibit the use of these       
substances in milk4 ,their only function
 in the dairy should be to check        
fermentative and putrefactive processes 
outside of milk and so keep the air free
 from taints4  ,products of growth4 ,all
 bacteria1 as a result of their growth  

in food substances1 form more or less   
characteristic compounds that are known 
as by-products4 ,the changes brought    
about are those of decomposition and are
 collectively known as fermentations2   
they are characterized by the production
 of a large amount of by-products as the
 result of the development of a         
relatively small amount of cell life4   
,the souring of milk1 the rotting of    
eggs1 the spoiling of meats1 the making 
of vinegar from cider are examples of   
fermentations caused by different       
bacteria4  ,if the substances decomposed
 contain but little sugar1 as do animal 
tissues1 the conditions are favorable   
for the growth of the putrefactive      
bacteria1 and foul-smelling gases are   
formed4 ,when sugars are present1 as in 
milk1 the environmental conditions are  
most favorable for the acid-forming     
bacteria that do not as a rule produce  
offensive odors4  ,many of the bacteria 
form substances known as enzymes which  
are able to produce certain             

decomposition changes in the absence of 
the living cells1 and it is by virtue of
 these enzymes that the organisms are   
able to break down such enormous        
quantities of organic matter4 ,most of  
these enzymes react toward heat1 cold1  
and chemical poisons in a manner quite  
similar to the living cells4 ,in one    
respect1 they are readily               
differentiated1 and that is1 that       
practically all of them are capable of  
producing their characteristic chemical 
transformations under conditions where  
the activity of the cell is wholly      
suspended as in a saturated ether or    
chloroform atmosphere4 ,the production  
of enzymes is not confined to bacteria1 
but they are found throughout the animal
 and plant world1 especially in those   
processes that are concerned in         
digestion4 ,rennet1 used in cheese      
making1 is an example of an animal      
enzyme4  ,distribution of bacteria4 ,as 
bacteria possess greater powers of      
resistance than almost any other form of

 life1 they are found very widely       
distributed over the surface of the     
earth4 ,in soil they are abundant1      
because of the fact that all of the     
conditions necessary for growth are here
 best satisfied4 ,they are1 however1    
distributed with reference to the layers
 of the soil2 the soil proper1 i4e41    
that turned over by the plow1 is        
extremely rich in them on account of the
 abundance of organic matter4 ,but at   
the depth of a few feet they decrease   
rapidly in numbers1 and in the deeper   
layers1 from six to ten feet1 or more1  
they are normally not present1 because  
of the lack of proper food supply and   
oxygen4 ,the fertility of the soil is   
closely associated with their presence4 
,the bacteria are found in the air      
because of their development in the soil
 below4 ,they are unable to grow even in
 a moist atmosphere1 but are so readily 
dislodged by wind currents from the soil
 that over land areas the lower strata  
of the air always contain them4 ,they   

are more numerous in summer than in     
winter2 city air contains larger numbers
 than country air4 ,wherever dried fecal
 matter is present1 as in barns1 the air
 contains many forms4  ,water generally 
contains enough organic matter in       
solution1 so that certain types of      
bacterial life find favorable growth    
conditions4 ,water in contact with the  
soil surface takes up many impurities1  
and is of necessity rich in bacteria4   
,as the rain water percolates into the  
soil1 it loses its germ content1 so that
 the normal ground water1 like the      
deeper soil layers1 contains practically
 no bacterial life4 ,springs1 therefore1
 are relatively deficient in germ life1 
except as they become contaminated with 
soil organisms1 as the water issues from
 the ground4 ,wells vary in their germ  
content1 depending upon manner of       
construction1 ease of contamination at  
surface1 etc4 ,wells are too frequently 
insufficiently protected from surface   
leachings1 and consequently may contain 

all kinds of organisms found in the     
surface soil4 ,typhoid fever is very    
frequently disseminated in this way1 as 
is cholera and a number of animal       
maladies4  ,while the inner tissues of  
healthy animals are free from bacteria1 
the natural passages1 as the respiratory
 and digestive tracts1 being in more    
direct contact with the exterior1 become
 readily infected4 ,this is particularly
 true with reference to the intestinal  
tract1 and in the undigested residue of 
the food1 bacterial activity is at a    
maximum4 ,the result is that fecal      
matter of all kinds contains enormous   
numbers of organisms so that the        
pollution of any food medium1 such as   
milk1 with such material is sure to     
introduce elements that seriously affect
 its quality4     ,,chapter ,,ii4       
,,methods ,,of ,,studying ,,bacteria4   
,necessity of artificial cultivation4   
,the bacteria are so extremely small1   
that it is impossible to study          
individual germs separately without the 

aid of powerful microscopes4 ,little    
advance was made in the knowledge of    
these lower forms of plant life until   
the introduction of culture methods1    
whereby a single organism could be      
cultivated1 and the progeny of this cell
 increased to such an extent in a short 
course of time that the resulting mass  
of cells would be visible to the unaided
 eye4 ,this is done by growing the      
bacteria on various kinds of nutrient   
media that are prepared for the purpose1
 but inasmuch as bacteria are so        
universally distributed1 it becomes an  
impossibility to cultivate any special  
form alone1 unless the medium in which  
they are grown is first freed from all  
pre-existing forms of germ life4  ,food 
materials4 ,many kinds of food          
substances are used for the cultivation 
of bacteria in the laboratory4 ,in fact1
 bacteria will grow on almost any       
organic substance1 whether it is solid  
or liquid1 provided the other essential 
conditions of growth are furnished4 ,the

 food substances that are used for      
culture purposes are divided into two   
classes1--solids and liquids4  ,solid   
culture media may be either permanently 
solid1 like potatoes and coagulated egg1
 or they may retain their solid         
properties only at certain temperatures1
 like gelatin or agar4 ,the latter two1 
which were devised by ,robert ,koch1 are
 of utmost importance in bacteriological
 research1 for their use permits the    
separation of the different forms of    
bacteria that may happen to be in any   
mixture4 ,gelatin is advantageously     
used1 because the majority of bacteria  
present wider differences1 due to growth
 upon this medium1 than upon any other4 
,it remains solid at ordinary           
temperatures1 becoming liquid at about  
#hj ,f4 ,agar1 a gelatinous product     
derived from a ,japanese seaweed1 has a 
much higher melting point1 and is used  
especially with those organisms whose   
optimum temperature for growth is above 
the melting point of gelatin4  ,besides 

these solid culture media1 different    
liquid substances are extensively used1 
such as beef broth1 milk and infusions  
of various vegetable and animal tissues4
 ,skim milk is of especial value in     
studying the milk bacteria1 and may be  
used in its natural condition1 or a few 
drops of litmus solution may be added1  
in order to detect any change in its    
chemical reaction due to the bacteria4  
,sterilization4 ,the various ingredients
 that are used in the preparation of    
culture media are not free from         
micro-organisms1 hence the media would  
soon spoil if they were not destroyed1  
and the media subsequently protected    
from contamination from the air1 etc4   
,the process of rendering the media free
 from living micro-organisms is known as
 sterilization4 ,it may be accomplished 
in a number of ways1 but most often is  
done by the use of heat4 ,for culture   
material1 which is always organic in    
character1 moist heat is employed4 ,the 
various culture media1 in appropriate   

containers1 are subjected to a thorough 
steaming in a steam cooker4 ,this       
destroys all of the vegetating cells but
 not the resistant spores that may be   
present4 ,the media are then stored1 for
 twenty-four hours1 at temperatures     
favorable for the germination of the    
spores and are then again heated4 ,three
 such applications on successive days   
are usually sufficient to free the media
 from all living germs1 since between   
the heating periods the spores germinate
 and the resulting vegetative cells are 
more easily destroyed4 ,the sterile     
media will keep for an indefinite period
 in a moist place4  ,the media are      
usually placed in glass containers which
 may be sterilized before use by heating
 them in an oven1 it being possible to  
thus secure a much higher temperature   
than with streaming steam4 ,all glass or
 metal articles may be sterilized by the
 use of dry heat but for organic media1 
to avoid burning1 moist heat must be    
used4  ,all kinds of materials may be   

sterilized by treatment with steam under
 pressure4 ,an exposure for a few       
moments at #bej ,f41 a temperature      
attained with #ae pounds steam pressure1
 will destroy all kinds of bacteria and 
their spores4 ,this method of           
sterilization is used in the canning of 
meats and vegetables and in the         
preparation of evaporated milk4 ,to     
avoid contamination of the media after  
sterilization1 the flasks and tubes are1
 after being filled1 stoppered with     
plugs of cotton-wool1 which effectually 
filter out all bacteria and mold spores 
from the air1 and yet allow the air to  
pass freely in and out of the           
containers4  ,methods of determining the
 number of bacteria4 ,the method of     
determining the number and kinds of     
bacteria in any substance can be        
illustrated by the process as applied to
 milk4 ,for this purpose the method of  
procedure is as follows3 ,sterile       
gelatin in glass tubes is melted and    
then cooled until it is barely warm4 ,to

 this melted gelatin a definite quantity
 of milk is added4 ,the medium is gently
 shaken1 so as to thoroughly mix the    
milk and gelatine1 and the mixture then 
poured into a sterile1 flat1 glass dish1
 and quickly covered1 where it is       
allowed to cool until the gelatin       
hardens4 ,after the culture plate has   
been left for twenty-four to thirty-six 
hours at the proper temperature1 tiny   
spots will begin to appear on the       
surface1 or in the depth of the         
culture-medium4 ,these spots are called 
colonies1 and are composed of an almost 
infinite number of individual cells1 the
 result of the continued growth of a    
single organism that was in the drop of 
milk and which was firmly held in place 
when the gelatin solidified4 ,the number
 of these colonies represents           
approximately the number of living      
bacteria that were present in the amount
 of milk added to the tube of gelatin4  
,if the plate is not too thickly sown   
with the bacteria1 the colonies will    

continue to grow and increase in size1  
and as they do1 minute differences will 
begin to appear4 ,these differences may 
be in the color1 the contour1 and the   
texture of the colony1 or the manner in 
which it acts toward gelatin4           
,illustration3 ,fig4 #d4--,plate        
,culture4  ,each of the dots is a colony
 that has been formed by the growth of  
an organism embedded in the solid       
culture-medium4 ,by counting the        
colonies1 the number of living bacteria 
in the amount of milk added to the      
culture is determined4  ,in order to    
make sure that the number of colonies is
 not so numerous as to prevent counting 
and further study of their              
characteristics1 a series of plate      
cultures is usually made in which       
varying amounts of milk are added to the
 tubes of gelatine4 ,this is attained by
 adding a definite amount of the milk or
 other substance to be examined to a    
measured amount of sterile water1 e4g41 
one cubic centimeter of milk to         

ninety-nine cubic centimeters of water4 
,one cubic centimeter of this mixture   
may be used for the inoculation of the  
plate culture4 ,this dilution may be    
carried on to any desired extent2 in the
 examination of many dairy products1 it 
is necessary to use very minute         
quantities of material1 often only one  
one-millionth of a cubic centimeter4    
,to study further the peculiarities of  
the different bacteria1 small portions  
of the individual colonies are          
transferred to tubes of sterile         
culture-media4 ,in order to do this the 
colony is touched with a piece of       
platinum wire2 the minute amount of     
growth that adheres to the wire is      
sufficient to seed the tube of fresh    
culture-medium4 ,the inoculating needle 
must always be sterilized before use by 
passing it through a gas flame4  ,a     
culture thus obtained is called a pure  
culture since it contains but a single  
kind of an organism1 as the colony is   
the result of the growth of a single    

cell4 ,these cultures then serve as a   
basis for continued study1 and must be  
planted and grown upon the different    
kinds of media that are obtainable4 ,in 
this way the slightest variations in the
 growth of different forms are detected1
 and the peculiar characteristics are   
determined1 so that the student is able 
to recognize this form when he meets it 
again4  ,illustration3 ,fig4            
#e4--;,different ,kinds of ,bacteria    
,growing in ,gelatin4  ,a1 meager       
growth1 no liquefaction or surface      
growth2 ,b1 profuse surface growth1     
radiating filaments from the growth     
below the surface2 ,c1 a rapid          
liquefying form2 ,d1 a gas producer that
 grows equally well in the presence or  
absence of air2 ,e1 form that grows only
 in the absence of air1 an anaerob4     
,these culture methods are of essential 
importance in bacteriology1 as it is the
 only way in which it is possible to    
secure a quantity of germs in a pure    
state4  ,the microscope in bacterial    

investigations4 ,in order to verify the 
purity of the cultures1 the microscope  
is in constant demand throughout all the
 different stages of the isolating      
process4 ,for this purpose it is        
essential that the instrument used shall
 be one of high magnifying powers 7#fjj 
to #hjj diameters71 combined with sharp 
definition4  ,the microscopical         
examination of any germ is quite as     
essential as the determination of       
culture characteristics1 in fact1 the   
two must go hand in hand4 ,the          
examination reveals not only the form   
and size of the individual germs but the
 manner in which they are united with   
each other1 as well as any peculiarities
 of movement that they may possess4  ,in
 carrying out the microscopical part of 
the work1 not only is the organism      
examined in a living condition1 but     
colored preparations are made by using  
solutions of anilin dyes as staining    
agents4 ,these are of great service in  
bringing out almost imperceptible       

differences4 ,the art of staining has   
been carried to the highest degree of   
perfection in bacteriology1 especially  
in the detection of germs that are found
 in diseased tissues in the animal or   
human body4  ,in studying the           
peculiarities of any special organism1  
not only is it necessary that these     
cultural and microscopical characters   
should be closely observed1 but special 
experiments must be made in different   
ways1 in order to determine any special 
properties that the germ may possess4   
,thus1 the ability of any form to act as
 a fermentative organism can be tested  
by fermentation experiments2 the        
property of causing disease1 studied by 
the inoculation of pure cultures into   
experimental animals1 like rabbits1     
guinea pigs and white mice4  ,the       
methods of the bacteriologist in his    
laboratory are in their effect not      
dissimilar to those which the farmer    
employs in securing his crop of         
pure-bred grain4 ,the laboratory farmer 

kills the weed seeds in his culture     
field by the application of heat4 ,his  
field1 which is embraced in his culture 
dish1 has been fertilized and prepared  
by the addition of certain favorable    
ingredients4 ,when he has garnered his  
crop1 he maintains its purity by keeping
 his selected seed1 the pure culture1   
free from all contamination4 ,the       
dairyman1 even though he may not expect 
to carry on the detailed operations of  
the laboratory1 will understand the     
reason for the directions which he is   
often required to follow much better if 
he knows how the simple operations of   
the laboratory are carried out4 ,for a  
fuller knowledge of these matters1 the  
reader is referred to the special texts 
on bacteriology4     ,,chapter ,,iii4   
,,contamination ,,of ,,milk4   ,spoiling
 of milk4 ,materials of animal origin   
are peculiarly prone to undergo changes1
 rendering them unfit for use1 and of   
these1 milk is exceedingly susceptible  
to such changes4 ,this is due to the    

fact that the composition of milk is    
especially adapted to bacterial growth1 
and that the opportunity for entrance of
 such organisms is likewise such as to  
permit of abundant contamination4 ,the  
consequence is that milk readily        
undergoes fermentative changes1 due to  
the development of one or another type  
of micro-organism4  ,milk1 a suitable   
bacterial food4 ,while milk is designed 
by nature for the nourishment of        
mammalian life1 it is1 curiously enough1
 equally well adapted to the growth of  
these lowest forms of vegetable life4   
,the nutritive substances required by   
bacteria are here sufficiently dilute to
 make possible rapid growth4  ,milk also
 contains all the necessary chemical    
substances to make a suitable bacterial 
food supply4 ,of the nitrogenous        
compounds1 albumen is in a readily      
assimilable form4 ,casein1 the principal
 nitrogenous constituent of milk1 exists
 in an insoluble condition1 and cannot  
be directly utilized1 until it is acted 

upon by digesting enzymes4 ,the fat in  
milk does not readily decompose1 and    
while there are a few bacteria capable  
of splitting this substance1 the        
majority of organisms are unable to     
utilize it4 ,milk sugar1 on the other   
hand1 is an excellent food for most     
species4  ,illustration3 ,fig4          
#f4--;,fat ,globules and ,bacteria4     
,note the relative size of the fat      
globules of milk and the lactic acid    
bacteria4  ,sources of contamination4   
,inasmuch as milk is especially exposed 
to the inroads of bacterial growth1 and 
because of the fact that much of the    
contamination can easily be prevented1  
it is highly important that the milk    
producer and dealer should be thoroughly
 cognizant of the various sources of    
contamination4 ,the different factors   
concerned in contamination may be       
grouped as follows3 the interior of the 
udder2 utensils1 including all apparatus
 with which the milk is brought in      
contact subsequent to withdrawal from   

the animal2 infection coming from the   
animal herself1 from the milker1 and the
 surrounding air4  ,condition of milk   
when secreted4 ,immediately after       
withdrawal from the udder1 milk always  
contains bacteria1 yet in the secreting 
cells of the udder of a healthy cow1    
germ life does not seem to be present4  
,only when the gland is diseased are    
bacteria found in any abundance4 ,in the
 passage of the milk from the secreting 
cells to the outside1 it receives its   
first infection1 so that when drawn from
 the animal it generally contains a     
considerable number of organisms4  ,a   
study of the structure of the udder     
shows the manner in which such infection
 occurs4  ,structure of the udder4 ,the 
udder is composed of secreting tissue   
7gland cells7 that is supported by      
fibrous connective tissue4 ,the milk is 
elaborated in these cells and is        
discharged into microscopic cavities1   
from whence it flows through the        
numerous channels 7milk sinuses7 that   

ramify through the substance of the     
udder1 until finally it is conveyed into
 the milk cistern1 a common receptacle  
holding about one half pint that is     
located just above the teat4 ,this      
cavity is connected with the outside by 
a direct opening 7milk duct7 through the
 teat4 ,during the process of milking1  
the milk is elaborated rapidly in the   
gland cells1 and their contents upon    
rupture of the milk cells1 flow down    
into the cistern4 ,the normal           
contraction of the muscles at the lower 
opening of the outer duct prevents the  
milk from passing out except when       
pressure is applied1 as in milking4 ,the
 inner walls of the milk duct and       
cistern are always more or less moist1  
and therefore afford a suitable place   
for bacteria to develop1 if infection   
once occurs1 and conditions are         
favorable for growth4  ,manner of       
invasion4 ,two possible sources of      
invasion of the udder by bacteria may   
exist4 ,if bacteria are present in the  

circulating blood1 there is the         
possibility of organisms passing        
directly through the tissues into the   
milk-secreting cells4 ,the other        
alternative is the possible direct      
contamination from the outside by       
organisms passing up through the milk   
duct1 and so spreading through the open 
channels in the udder4  ,illustration3  
,fig4 #g4--,sectional ,view of ,udder4  
,teat with milk duct connecting the     
exterior with the milk cistern4 ,milk   
sinuses which conduct the milk from the 
secreting tissue to the milk cistern4   
7,after ,moore  ,ward47  ,number of     
bacteria in fore-milk4 ,if a            
bacteriological examination is made of  
the milk drawn from each teat at        
different periods during the milking    
process1 it will be found that the      
fore-milk1 i4e41 the first few streams1 
contains1 as a rule1 many more organisms
 per cubic centimeter than that removed 
later4 ,not infrequently thousands of   
organisms per cubic centimeter may be   

found in the first streams while the    
middle milk1 or strippings1 will contain
 much smaller numbers4  ,distribution   
and nature of bacteria in udder4 ,if the
 udder itself is carefully examined as  
to its bacterial content1 it appears    
that the majority of organisms found is 
confined to the lower portion of this   
organ1 in the teat1 milk-cistern and    
large milk-ducts2 while bacteria occur  
in contact with the secreting tissue1   
they are relatively less abundant4 ,this
 would seem to indicate that the more   
probable mode of infection is through   
the open teat4  ,while there is no      
constant type of bacteria found in the  
fore-milk1 yet it is noteworthy that    
nearly all observers agree that the     
organisms most commonly found are not   
usually the acid-producing1 or          
gas-generating type1 so abundant on the 
skin or hairy coat of the udder and     
which predominate in ordinary milks4    
,coccus forms1 belonging to both        
liquefying and non-liquefying types are 

most generally present4 ,many of these  
produce acid slowly and in small        
quantities4  ,the bacteria coming from  
the interior of the udder are of small  
practical significance since they do not
 grow rapidly at the temperatures at    
which milk is stored4 ,if the milk is   
protected from contamination from other 
sources1 the bacteria from the udder    
will ultimately cause it to spoil1 but  
under ordinary conditions other forms   
are present in such greater numbers1 and
 grow so much more rapidly in milk1 that
 the udder forms have small opportunity 
to exert any effect4  ,it is interesting
 to note that the bacteria found in the 
udder are similar to those that seem to 
be most abundant in such glandular      
tissues as the liver and spleen4 ,this  
fact increases the probability that     
these comparatively inert coccus forms  
of the udder may originate directly from
 the blood stream4 ,the organisms that  
normally are found in the udder exert no
 harmful effects on the gland4 ,it might

 be thought that due to the presence of 
abundant food and a favorable           
temperature that growth would be        
abundant1 but such is not the case4 ,at 
times the udder may be invaded by forms 
that are not held in check by the       
natural factors and an inflammation of  
the udder is likely to result4          
,germicidal property of milk4 ,it has   
been claimed that freshly drawn milk1   
like other body fluids1 possesses       
germicidal properties1 i4e41 the power  
of destroying bacteria with which it may
 be brought in contact4 ,if milk is     
carefully examined bacteriologically1   
hour by hour1 after it is withdrawn from
 the udder1 it will generally be found  
that there is at first not only no      
increase in number of organisms during a
 longer or shorter period when it is    
kept at temperatures varying from #dj to
 #gj ,f41 but that an actual reduction  
not infrequently takes place4 ,when     
cultures of bacteria1 such as ,b4       
prodigiosus1 a red organism1 lactic acid

 organisms1 and even the yellow1        
liquefying coccus1 so commonly found in 
the fore-milk1 are artificially         
introduced into the udder1 it has been  
found that no growth occurs and that in 
the course of a few days the introduced 
organisms actually disappear4 ,whether  
this failure to colonize can be regarded
 as evidence of a germicidal property or
 not is questionable4 ,in fact1 this    
question is a matter of but little      
practical importance in the handling of 
milk since1 under the best of           
conditions1 the keeping quality of the  
milk is not materially enhanced4 ,it may
 be of importance in inhibiting growth  
in the udder4  ,rejection of fore-milk4 
,the fact that the fore-milk contains   
per cubic centimeter so much more germ  
life than the remainder of the milk has 
led some to advocate its rejection when 
a sanitary milk supply is under         
consideration4 ,while from a purely     
quantitative point of view1 this custom 
may be considered advantageous1 in      

practice1 however1 it is hardly worth   
while since it is not at all certain    
that the rejection will have any effect 
on the keeping quality or healthfulness 
of milk4 ,this is especially true if the
 ends of the teats are thoroughly       
cleaned before milking4 ,it is true that
 the fore-milk is relatively deficient  
in fat so that the loss of butter fat   
occasioned by the rejection of the first
 few streams is comparatively slight4   
,contamination from utensils4 ,one of   
the most important phases of            
contamination is that which comes from  
the utensils used to hold the milk from 
the time it is drawn until it is        
utilized4 ,not only is this important   
because it is a leading factor in the   
infection of milk1 but because much     
improvement can be secured with but     
little trouble1 and it is especially    
necessary that the dairy student should 
be made familiar with the various       
conditions that obtain4 ,pails and cans 
used to hold milk may be apparently     

clean to the eye1 and yet contribute    
materially to the germ content of the   
milk placed in them4 ,not only does much
 depend upon their condition1 but it is 
equally important to take into          
consideration their manner of           
construction4 ,dairy utensils should be 
simple in construction1 rather than     
complex4 ,they should be made so that   
they can be readily and easily cleaned1 
or otherwise the cleaning process is apt
 to be neglected4  ,of first importance 
are those utensils that are used to     
collect the milk and in which it is     
handled while on the farm4 ,the warm    
milk is first received in pails1 and    
unless these are scrupulously cleaned1  
an important initial contamination then 
occurs4 ,as ordinarily washed1 the      
process falls far short of ridding the  
utensils of the bacterial life that is  
adherent to the inner surface of the    
pail4 ,then1 too1 all angles or crevices
 afford an excellent hiding place for   
bacteria1 and it is very important to   

see that all seams are well soldered4   
,round corners and angles flushed with  
solder greatly facilitate thorough      
cleaning of utensils4 ,tin utensils are 
recognized as most satisfactory4        
,shipping cans are likely to serve as   
greater infecting agents than pails for 
they are subject to more wear and tear  
and are harder to clean4 ,as long as the
 surface is bright and smooth1 it may be
 easily cleaned1 but large utensils1    
such as cans1 are likely to become      
dented and rusty in spots on the inner  
side4 ,the storage of milk in such      
utensils results in its rapid           
deterioration4 ,the action of rennet has
 been found to be greatly retarded where
 milk comes in contact with a rusty iron
 surface4 ,it is also probable that some
 of the abnormal flavors in butter are  
due to the action of acid cream on iron 
or copper surfaces from which the tin   
has been worn4 ,it is equally important 
that attention be paid to the care of   
strainers1 coolers1 and the small       

utensils4 ,cloth strainers are more or  
less of a hotbed for bacterial growth1  
for unless they are boiled1 and then    
dried quickly and thoroughly1 germ      
growth will continue apace in them1 as  
long as they contain any moisture4      
,milking machines and farm separators4  
,the introduction of these special types
 of dairy machinery in the handling of  
milk on the farm has materially         
complicated the question of the care of 
milk4 ,both of these types of apparatus 
are much more complicated than the usual
 milk utensil2 consequently1 the danger 
of imperfect cleaning is thereby        
increased4 ,this is still further       
accentuated by the fact that cleansing  
of utensils on the farm can never be    
done so well as at the factory or milk  
depot where steam is available4 ,the    
milking machine may be easily kept in a 
comparatively germ-free condition1 but  
unless this is done1 it contributes its 
quota of germ life to the milk4  ,the   
farm separator is more widely used than 

the milking machine and in actual       
practice the grossest carelessness      
prevails in the matter of its care4     
,frequently it is not taken apart and   
thoroughly cleansed1 but is rinsed out  
by passing water through the machine4   
,it is impossible by such a treatment to
 remove the slime that collects on the  
wall of the bowl2 the machine remains   
moist and bacterial growth can go on4   
,such a machine represents a most       
important source of contamination of    
milk and cream and it is probable that  
the widespread introduction of the hand 
separator has contributed more to lower 
the quality of cream delivered at the   
factory than any other single factor4   
,contamination from factory by-products4
 ,the custom of returning factory       
by-products in the same set of cans that
 is used to bring fresh milk is a       
prominent cause of bad milk4 ,whey and  
skim milk are rich in bacterial life1   
and not infrequently are so handled as  
to become a foul1 fermenting mass4 ,if  

the cans used to transport this material
 are not scrupulously cleaned on the    
farm1 transfer of harmful bacteria to   
the milk is made possible4 ,in this way 
the carelessness of a single patron may 
be the means of seeding the whole       
factory supply4 ,this custom is not only
 liable to produce a poor quality of    
milk1 but it is more or less of a menace
 to all the patrons of a factory1       
inasmuch as the opportunity always      
obtains that disease-producing organisms
 may thus be introduced into the supply4
 ,not infrequently is tuberculosis thus 
spread through the medium of factory    
by-products4  ,illustration3 ,fig4      
#h4--,whey ,disposal4  ,whey barrels at 
a ,wisconsin ,swiss cheese factory4     
,each patron's share is placed in a     
barrel which is so situated that it is  
impossible to empty it completely2 thus 
it is not cleaned during the season4    
,the manufacture of ,swiss cheese       
presents a striking example of the      
disregard which factory operators show  

toward the employment of bacteriological
 principles4 ,in these factories1 the   
custom is widely practiced of           
apportioning the patrons' allotment of  
whey into individual barrels which are  
supposed to be emptied each day4 ,as    
these barrels are1 however1 rarely ever 
cleaned from the beginning to the end of
 the season1 they become very foul1 and 
the whey placed in them from day to day 
highly polluted4 ,it is this material   
which is taken back to the farms in the 
same set of cans that is used for the   
fresh milk4 ,when one recalls that the  
very best type of milk is essential for 
the making of a prime quality of ,swiss 
cheese1 and that to secure such1 the    
maker insists that the patron bring the 
product to the factory twice daily1 the 
before mentioned practice appears       
somewhat inconsistent4  ,treatment of   
factory by-products4 ,to overcome the   
danger of infecting milk from factory   
by-products with either undesirable     
fermentative organisms1 or              

disease-producing bacteria1 the most    
feasible process is to destroy these    
organisms by the application of heat4   
,in ,denmark1 some portions of ,germany1
 and in some of the states in this      
country1 laws exist which require the   
heating of all skim milk before it is   
returned to the farm4 ,this is done by  
the direct use of exhaust steam1 or     
running the product through heaters4    
,the treatment of whey in cheese factory
 practice is especially important since 
the warm whey must be stored for a      
number of hours before it is returned to
 the farms4 ,even under the best of     
conditions the whey is certain to be in 
an advanced state of fermentation when  
placed in the milk cans1 and it only    
needs the infection of the whey tank    
with harmful bacteria to cause great    
loss on account of the injury of the    
product by these bacteria4 ,among       
,canadian factories the custom of       
heating the whey as it passes from the  
cheese vat to whey tank has been        

introduced1 and where ever adopted has  
been retained1 because1 it has resulted 
in such an improvement of the cheese    
that the gain was much greater than the 
cost1 which is estimated at not over    
fifty cents per ton of cheese4 ,the whey
 is heated not to exceed #aee ,f42 the  
hot whey serves to scald the whey tank  
and as the mass of whey is usually quite
 large1 it does not cool to a point     
where bacterial growth can take place   
for a number of hours4 ,the whey is thus
 quite sweet when returned to the farm  
and has greater feeding value4 ,the     
heating also prevents the creaming of   
the whey in the tank and thus avoids the
 soiling of the cans with grease which  
is most difficult to remove4  ,where    
compulsory legislation is in force it is
 generally required that these          
by-products be heated to a temperature  
of at least #agf ,f4 ,this is done so as
 to destroy effectually the organisms of
 tuberculosis1 and especially to permit 
of the utilization of the so-called     

,storch test1#a which enables a person  
to determine quickly whether milk or    
whey has been heated or not4      #a    
,storch 7#dj ,rept4 ,expt4 ,stat41      
,copenhagen1 #ahih7 has devised     a   
test whereby it can be determined       
whether this treatment has     been     
carried out or not2 milk contains a     
soluble enzyme known as     peroxidase  
which has the property of decomposing   
hydrogen     peroxid4 ,if milk is heated
 to #agf ,f41 7#hj ,c47 or above1 this  
enzyme is destroyed1 so that the above  
reaction no longer takes     place4 ,if 
potassium iodide and starch are added to
 unheated milk     and the same treated 
with hydrogen peroxid1 the decomposition
 of     the latter agent releases oxygen
 which acts on the potassium     salt1  
which in turn gives off free iodine that
 turns the starch     blue4  ,cleaning  
utensils4 ,various processes are applied
 to dairy utensils to cleanse them4 ,in 
removing visible dirt and foreign       
matter1 much of the bacterial life is   

mechanically eliminated1 but most of the
 cleaning processes fail to destroy the 
germ life in these utensils4  ,in       
rinsing1 washing1 or even scalding1 the 
water is not applied at a sufficiently  
high temperature to destroy effectively 
the bacteria4 ,these processes are      
primarily used for the removal of dirt  
and other matter4 ,to facilitate such   
removal1 washing powders of various     
kinds are frequently employed2 some of  
these possess considerable disinfecting 
action4 ,all utensils after cleansing   
should be thoroughly rinsed in clean1   
hot water4 ,even where no further       
treatment is given1 a careful cleaning  
may so reduce the germ content on the   
inner surface of utensil as to render   
contamination therefrom relatively      
unimportant4 ,most of the contamination 
in a well cleaned utensil comes from the
 cracks and angles1 which permit of the 
collection of the dirt4 ,if these are   
properly attended to1 thorough cleaning 
and rinsing alone will accomplish much4 

,to exert an actual germ-destroying     
effect on the bacterial content of the  
utensil1 resort must be had to boiling  
or steaming4 ,to treat utensils so as to
 render them wholly germ-free would be  
impractical under ordinary commercial   
conditions1 as it would consume too much
 time1 although with proper apparatus1  
this process is not impossible1 but it  
is well within the limits of            
practicability in factory treatment to  
apply steam for a short period of time4 
,where cans1 pails and such utensils1   
are steamed for a minute or so after    
being thoroughly cleaned1 the germ      
content is greatly reduced4 ,in a series
 of tests by ,harrison1 the germ content
 of a set of cans cleaned in an ordinary
 way was #ddb1jjj bacteria per cubic    
centimeter in #ajj cubic centimeters of 
wash water2 in a set washed in tepid    
water and then scalded--the best farm   
practice--it was #ed1jjj per cubic      
centimeter1 while in cans carefully     
washed and then steamed for #e minutes1 

it was reduced to #hhj per cubic        
centimeter4 ,it would not be worth while
 to institute measures that would       
accomplish the destruction of this small
 residual content4  ,the use of steam1  
therefore1 is of great service in       
eliminating bacterial life in all       
utensils4 ,in apparatus of at all       
complicated design1 it is absolutely    
necessary4 ,of course1 ordinarily1 steam
 can be applied only at the factory1 as 
the farm does not usually afford        
facilities for its easy generation4     
,this fact has led in some cases to the 
adoption of the method of cleaning and  
sterilizing the cans at the factory     
rather than to await their arrival at   
the farm4 ,this custom is most          
frequently followed in milk supply      
plants4  ,it is also very important in  
cleaning dairy utensils to see that they
 are rapidly and thoroughly dried after 
being washed and steamed4 ,as pointed   
out above1 the short period of steaming 
that can be followed in practice does   

not kill all the bacteria4 ,if moisture 
is retained1 conditions permit of the   
growth of the undestroyed organisms4    
,tests made on glass milk bottles showed
 that considerable growth occurred in   
the condensation water even after quite 
thorough sterilization4 ,some of the    
devices used for the sterilization of   
such utensils as milk cans are so       
arranged that1 after steam has been     
introduced1 hot air is passed into the  
can until it is thoroughly dried4 ,other
 utensils such as cloth strainers become
 sources of contamination unless the    
articles are thoroughly and quickly     
dried after cleaning4  ,in a general    
way1 it may be said that whenever a     
utensil is so constructed and in such a 
condition that every portion of its     
surface can be reached by a cloth or a  
brush1 it can be kept in a sanitary     
condition4 ,but whenever any portion    
cannot be thus reached1 whether it is an
 angle or a seam in a pail or can1 the  
interior of the separator bowl1 or in   

the pipes used for conducting milk1     
contamination is certain to result from 
such places1 unless extreme care is     
taken to destroy the bacteria therein by
 steaming4  ,contamination from the     
animal4 ,in the process of milking1 the 
bacterial content of the milk is        
materially increased4 ,in part this     
comes from the utensils into which the  
milk is drawn1 but the animal herself1  
the milker1 as well as the surrounding  
air1 also contribute to a varying       
extent4 ,of these factors1 the one      
fraught by far with the most            
consequence1 is the influence of the    
animal herself4 ,it is a popular belief 
that the organisms found in milk are    
derived from the feed and water which   
the animal consumes1 but under normal   
conditions1 the bacteria consumed in    
food pass through the intestinal canal  
and do not appear in the circulation4   
,it must not be assumed1 however1 that  
the character of feed and water supply  
is of no moment4 ,stock should be given 

pure and wholesome water and no         
decomposed or spoiled food should be    
used4  ,the infection traceable directly
 to the cow is modified materially by   
the conditions under which the animal is
 kept and the character of the feed     
consumed4 ,the nature of the fecal      
matter is in part dependent upon the    
character of the food4 ,the more        
nitrogenous the ration fed1 the softer  
are the fecal discharges1 producing a   
condition which is more likely to soil  
the coat of the animal unless care is   
taken4 ,the same is true with animals   
kept on pasture in comparison with those
 fed dry fodder4  ,stall-fed animals1   
however1 are more likely to have their  
flanks fouled1 unless special attention 
is paid to the removal of the manure4   
,all dairy stalls should be provided    
with a manure drop which should be      
cleaned as frequently as circumstances  
will permit4  ,illustration3 ,fig4      
#i4--;,bacteria on ,hairs4  ,each colony
 on the hair represents one or more     

bacteria that were adherent to the hair 
when it was placed on the surface of the
 solid culture-medium4  ,the animal     
contributes materially to the quota of  
germ life finding its way into the milk 
through the dislodgment of dust and     
filth particles adhering to its hairy   
coat4 ,the nature of this coat is such  
as to favor the retention of these      
particles4 ,unless care is taken1 the   
flanks and udder become polluted with   
fecal matter1 which upon drying is      
displaced with every movement of the    
animal4 ,every hair or dirt particle so 
dislodged and finding its way into the  
milk-pail adds its quota of organisms to
 the liquid4 ,this can be readily       
demonstrated by placing cow's hairs on  
the moist surface of gelatin culture    
plates4 ,almost invariably bacteria will
 be found in considerable numbers       
adhering to such hairs1 as is indicated 
in ,fig4 #i4  ,dirt particles are even  
richer in germ life4 ,not only is there 
the dislodgment of hairs1 epithelial    

scales1 and masses of dirt and filth1   
but during the milking process1 as at   
all other times1 every motion of the    
animal is accompanied by a shower of    
invisible particles1 more or less       
teeming with bacterial life4 ,all of    
this material contains organisms that   
are more or less undesirable in milk4   
,bacteria concerned in gassy            
fermentations and those capable of      
producing obnoxious taints are          
particularly common1 so that this type  
of pollution is especially undesirable  
in milk4  ,amount of dirt in milk4 ,when
 one remembers that the larger part of  
fresh manure is of such a nature that it
 does not appear as sediment1 the       
presence of evident filth in milk must  
bespeak careless methods of handling4   
,the sediment or dirt test is used quite
 extensively to ascertain the amount of 
dirt milk may contain4 ,by means of a   
cotton filter1 the insoluble residue is 
removed and is made evident upon a layer
 of absorbent cotton4 ,milk that would  

show with difficulty any evidence of    
dirt upon ordinary examination reveals  
such defects very readily in this test4 
,exclusion of dirt4 ,it is better to    
keep bacteria out of milk1 so far as    
practicable1 rather than to attempt to  
remove them after they have once gained 
entrance4 ,as is usual1 prevention of   
trouble is much more easily accomplished
 than removing the difficulty after it  
once occurs4  ,illustration3 ,fig4      
#aj4--;,dirt from ,milk4  ,the dirt     
adherent to each of the filters was     
obtained from one pint of milk4 ,the    
milks tested were produced on different 
farms4  ,much reduction as to the amount
 of dirt that finds its way into milk   
may be accomplished by improved stable  
environment4 ,the fouling of the udder  
and flanks comes from wading in dirty   
water1 muddy yards1 and from improper   
type of stalls4 ,barnyards are often a  
disgrace through the accumulation of    
manure and seepage4 ,cows wading in such
 mire cannot but accumulate mud and     

filth to a material degree on the teats 
and udder4 ,greater care as to drainage 
of the barnyard and the paving of same  
with gravel1 cinders1 etc41 will permit 
of its being kept clean1 and so prevent 
the fouling of animals4 ,but more       
important than the yard is the stall    
which the animal occupies in the stable4
 ,the essential feature is to have a    
stall of such construction as to keep   
the animal out of her own manure when   
she lies down4 ,to accomplish this1 it  
is necessary to have a manure drop      
behind the stall proper so that the     
feces and urine are kept out of the bed 
of the stall as much as possible4       
,illustration3 ,fig4 #aa4--,the ,model  
,stall4  ,a stall of this type keeps the
 animals clean1 and thus aids greatly in
 producing good milk4  ,most of the     
stalls widely advertised in the farm    
press seek to accomplish this in one way
 or another1 usually by some arrangement
 by which the cow is forced back when   
standing and drawn forward on lying     

down4 ,in ,fig4 #aa a type of stall is  
illustrated that accomplishes this most 
successfully2 the essential feature     
being a #bc-;inch wood strip nailed to  
the stall floor immediately in front of 
the hind feet of the animal when in a   
standing position4 ,when the animal lies
 down1 she crowds forward to avoid lying
 on this strip1 and thus is out of      
contact with the manure1 except such as 
is carried onto the bedding by the hind 
feet4 ,by the use of this stall it is   
possible to keep the animals free from  
all accumulations of manure4  ,effort   
should be made to prevent fouling of the
 animals rather than in cleaning them   
after once soiled4 ,it is very evident  
that where the cattle come to the milker
 with muddy udders1 they will not be so 
cleaned before milking as to prevent a  
large amount of such dirt from entering 
the milk4 ,however1 when all that can be
 done towards keeping the cows clean has
 been accomplished1 a small amount of   
grooming will greatly reduce the        

contamination coming from them4  ,the   
kind of bedding used in the stalls may  
have a marked influence on the          
contamination coming from the animal4   
,if the straw is dusty1 partially rotten
 and moldy1 the bacteria and molds      
adhere to the coat of the animal and are
 thus introduced into the milk4 ,in the 
case of cattle on pasture1 no visible   
evidences of dirt are usually present   
but the hair is covered with the dust   
coming from the soil4 ,there is very    
good reason to believe that the quality 
of milk is influenced by the type of    
pasture on which the cows graze1 due to 
the difference in the types of bacteria 
in the surface soil4 ,the milk from     
animals on low land is more likely to   
show undesirable fermentations than that
 from those grazing on higher lands4    
,this is not due to the influence of the
 feed as is often supposed but rather to
 the dirt from the coat of the animal4  
,washing the udder4 ,if a surface is    
moist1 dust and the adherent bacteria   

cannot be easily dislodged4 ,the air    
over snow-covered mountains or over     
oceans is relatively free from bacteria4
 ,the udder and flanks of the animals   
can be carded to remove the loose hairs 
and the evident dirt2 the fine dust can 
now be removed by wiping with a clean   
damp cloth just before the milking      
process4 ,the actual washing and wiping 
of the udder and flanks still further   
reduces the contamination coming from   
the animal2 experiments show a reduction
 of fully three-fourths of total        
contamination4 ,clipping the udder and  
flanks also aids in keeping the animal  
clean4  ,it is often asserted that the  
treatment of the animals in these ways  
reduces the yield of milk4 ,it is       
certain that such an effect will persist
 for only a short time and there is     
reason to believe that grooming         
increases the yield4  ,illustration3    
,fig4 #ab4--,sanitary ,milk ,pails4     
,the small opening is very efficient in 
keeping the dirt out of milk4  ,sanitary

 milk pails4 ,the entrance of organisms 
into the milk can be greatly reduced by 
lessening the area of the milk pail     
exposed to the dust shower4 ,to         
accomplish this purpose a number of     
so-called sanitary or hygienic milk     
pails have been devised4 ,in some cases1
 these are the regular type of pail     
provided with a cover having a small    
opening through which the milk is       
received4 ,in other cases1 a strainer is
 interposed so as to remove more        
effectually the coarse particles4 ,while
 pails of this type are successful in   
the removal of a large part of the dirt1
 and consequently reduce materially the 
bacterial content of the milk1 yet they 
must be of simple construction1 so that 
they can be kept in a clean condition in
 order to adapt them for general        
practical use4 ,the use of such a       
utensil increases materially the keeping
 quality of the milk4  ,illustration3   
,fig4 #ac4--,sanitary ,milk ,pails4     
,the ,stadtmueller pail and the ,truman 

pail1 two of the most practical of the  
small-topped pails4  ,stocking has shown
 that under ordinary barn conditions1   
the use of small-topped pails reduced   
the number of bacteria #ie per cent2    
with dirty cows the reduction in        
bacteria amounted to #ig per cent4 ,a   
six-inch opening presents only          
one-fourth as large an exposure as a    
twelve inch1 so that the reduction in   
bacterial content is greater than the   
lessening in the size of the openings of
 the pails4 ,the ordinary pail receives 
dust not only from the udder1 but also  
from the flank which is usually a more  
important source of contamination than  
the udder itself1 while the small-topped
 pail receives only that from the udder4
  ,illustration3 ,fig4 #ad4--use of     
,sanitary ,milk ,pails4  ,the open pail 
is fully exposed to the falling dust    
while the hooded pail excludes much of  
the dust and dirt coming from the       
animal4  ,milking machines4 ,where the  
milk is removed from the udder by       

machine methods1 instead of by hand1 it 
is possible to eliminate nearly all     
external contamination from the animal  
and her surroundings4 ,the only         
opportunity for infection is then       
through the leakage of air around the   
teat cups4 ,care should be taken to see 
that the teats are in a clean condition 
before applying the suction cups4 ,the  
main problem in the use of a milking    
machine is to keep the apparatus in an  
aseptic condition4 ,immersion of the    
teat cups and the rubber connections in 
lime water1 brine solution1 or other    
mild antiseptics1 prevents bacterial    
development4 ,hastings has found that   
milk having a germ content of less than 
#aj1jjj bacteria per cubic centimeter   
may be produced by the use of a properly
 handled milking machine4               
,contamination from the milker4 ,while  
the milker is a small factor in         
comparison with the animal in the matter
 of contamination1 yet he can not be    
neglected1 as it is within his power to 

affect profoundly the quality of the    
milk4 ,his personal habits as to        
cleanliness and his appreciation of the 
precautions necessary in the production 
of clean milk have much to do with the  
contamination of the milk4 ,the milking 
should be done with dry hands1 although 
a little vaseline may be used with      
effect4 ,the hands should be washed     
before milking as milk is certain to    
come in contact with them to some       
extent4 ,the milking should be done with
 the whole hand rather than stripping   
between the thumb and finger2 the       
clothing should be covered with clean   
overalls and jumper1 or at least a clean
 apron should be worn during the        
milking4 ,if these are of white         
material1 more frequent laundering is   
likely to result4  ,contamination from  
air4 ,it is difficult to disassociate   
the contamination arising from the      
condition of the air from that derived  
directly from the animal4 ,barn         
operations of various kinds result in   

the production of dust1 particularly    
where dry forage1 such as hay or straw1 
is handled4 ,where manure is given an   
opportunity to dry1 dust is readily     
produced1 and such material is          
particularly replete with bacterial     
life4 ,some kinds of dust1 such as that 
originating from ground grains1 or      
shavings that may be used for bedding1  
contain a small amount of bacterial life
 in comparison with the dust from hay1  
or other dry fodder4 ,in a dried        
condition1 the slightest movement is apt
 to dislodge these fine particles1 and  
they float in the air for considerable  
periods of time4 ,if milk is drawn and  
exposed to the air of the barn during   
the feeding operations1 it is subject to
 the dust shower that is present4 ,where
 the storage can is allowed to stand in 
the stable during the milking1 even     
though it is covered with a strainer1   
this accumulation of microscopic        
particles is added to the milk1 as they 
readily pass the meshes of the finest   

strainer4  ,illustration3 ,fig4         
#ae4--;contamination ,from the ,air4    
,this culture plate1 three inches in    
diameter1 was exposed for #cj seconds in
 the barn during feeding of dry fodder4 
,a #ab-;inch pail exposes over #ah times
 the surface of this plate4  ,removal of
 dirt after introduction4 ,the more     
primitive method of improving the       
quality of milk1 so far as its dirt     
content is concerned1 is to attempt to  
remove the grosser particles of         
contamination after entrance4 ,in the   
case of straining1 the method is usually
 applied at the time of milking1 but in 
the case of filtering and clarifying1 it
 is carried out at the milk station1 in 
an effort to improve the appearance of  
milk and overcome the influence of      
careless methods of the producer4 ,by   
the use of strainers1 either metallic or
 cloth1 it is possible to remove        
particles of hair1 undissolved dirt and 
manure1 but it must be remembered that  
these grosser visible particles of      

pollution are not really the cause of   
the troubles which may ensue in         
improperly handled milk4 ,the bacteria  
which are adherent to these foreign     
particles are in large measure washed   
off in the process of straining1 and    
pass through the meshes of the finest   
strainer4 ,the main service1 therefore1 
of straining is to improve the          
appearance of the milk1 and it has no   
effect on the quality in any way4       
,production of clean milk4 ,the problem 
of clean milk is important1 whatever may
 be the use to which milk may be put4   
,it is important in the manufacture of  
butter1 but owing to the fact that the  
fat is not readily acted upon by        
bacteria1 it is not so sensitive to     
bacterial conditions1 as when the milk  
is made into cheese4 ,in this product1  
the bacterial condition of the milk is a
 matter of prime importance4 ,in milk   
destined for direct consumption1 the    
exclusion of the bacteria becomes yet   
more important4 ,while it is impossible 

to exclude bacteria so completely that  
milk will not undergo fermentative      
changes1 yet for domestic consumption it
 is preferable to have milk with as low 
bacterial content as can readily be     
secured4 ,the highest type of market    
milk1 that known as sanitary1 or        
certified1 is produced under such       
extreme conditions of care as to contain
 the minimum germ content4 ,to          
accomplish these results requires such  
stringent control as to increase greatly
 the cost of the product4 ,pure1 clean  
milk can be produced at a very slight   
increase in cost over the regular       
expense of milk production1 if the right
 kind of attention is given to certain  
details of a practical character4       
,improvement in our milk supplies must  
largely come from this source1 for any  
improvement to be permanent must be made
 to pay1 and it requires considerable   
education to secure the co-operation of 
consumers and their willingness to pay  
for any material increase in the quality

 of the product4  ,in the foregoing     
factors concerned in the contamination  
of milk1 it is of course impossible to  
measure accurately the influence of the 
different sources of infection1 as these
 are continually subject to variation in
 every case4 ,as a rule1 the most       
important factors are those pertaining  
to the utensils and the condition of the
 animal herself4 ,if these two factors  
are brought under reasonable control1   
the major portion of contamination that 
ordinarily obtains is done away with4   
,the application of the remedial or     
preventive measures heretofore mentioned
 will greatly reduce the germ content of
 the milk4  ,cooling of milk on farm4   
,bacterial growth is directly related to
 temperature conditions1 and with summer
 temperatures1 such development goes on 
apace1 unless it is checked by early    
cooling4 ,the larger portion of bacteria
 that find their way into milk1         
especially those that are previously in 
contact with the air1 are in a dormant  

condition1 and are therefore not        
stimulated into immediate growth1 unless
 reasonably high temperatures prevail4  
,in milk1 which comes from the animal at
 blood heat1 this growth is greatly     
stimulated4 ,to counteract this effect1 
milk should be chilled as soon after    
milking as possible4 ,if the temperature
 is immediately lowered to #ej ,f41 or  
lower1 actual cell development is       
greatly retarded1 and the rate of       
souring1 and other fermentative changes 
thereby diminished4 ,in this country ice
 is liberally used in accomplishing this
 result4 ,in ,europe1 the use of ice is 
much less common4 ,the employment of    
such artificial means of refrigeration  
makes possible the shipment of milk for 
long distances by rail4 ,new ,york city 
now receives milk that is produced in   
,canada and northeastern ,ohio4         
,illustration3 ,fig4 #af4--;,effect of  
,cooling ,milk4  ,aeration of milk4 ,the
 custom has been extensively recommended
 of subjecting milk to the influence of 

air in the belief that such exposure    
permits of the interchange of gases that
 would improve the quality4 ,in         
practice1 this process1 known as        
aeration1 is carried on in different    
ways4 ,in some cases1 air is forced into
 the milk2 in others1 the milk is       
allowed to distribute itself in a thin  
sheet over a broad surface1 falling in  
drops or tiny streams through the air4  
,whenever this process is carried on at 
a temperature lower than that of the    
milk1 it results in more or less rapid  
cooling4  ,in earlier times1 aeration   
was generally recommended and practiced1
 especially in connection with the      
cheese industry1 but carefully          
controlled experiments fail to show that
 the process exerts any material        
influence on the rate of germ           
development4 ,if it is carried out in an
 atmosphere more or less charged with   
bacteria1 as in the barn or stable1 it  
is more than likely to add to the       
bacterial content of the milk4 ,while to

 some extent odors may be eliminated by 
the process1 the custom is not followed 
so generally now as it used to be some  
years ago4  ,absorption of taints4 ,a   
tainted condition in milk may result    
from the development of bacteria1 acting
 upon various constituents of the milk1 
and transforming these in such a way1 as
 to produce by-products that impair the 
flavor or appearance of the liquid2 or  
it may be produced by the milk being    
brought in contact with any odoriferous 
or aromatic substance1 under conditions 
that permit of the direct absorption of 
such odors4  ,this latter class of      
taints is entirely independent of       
bacterial action1 and is largely        
attributable to the physical property   
which milk possesses of absorbing       
volatile odors4 ,this direct absorption 
may occur before the milk is withdrawn  
from the animal1 or afterwards if       
exposed to strong odors4  ,it is not    
uncommon for the milk of animals        
advanced in lactation to have a more or 

less strongly marked odor and taste2    
sometimes it is apt to be bitter1 at    
other times salty to the taste4 ,it is a
 defect that is peculiar to individual  
animals1 and is liable to recur at      
approximately the same period in        
lactation4 ,the peculiar cowy or animal 
odor of fresh milk is an inherent       
peculiarity that is due to the direct   
absorption of volatile elements from the
 animal herself4  ,many kinds of feed   
consumed by the animal produce a more or
 less pronounced taint or flavor in the 
milk4 ,with some plants1 such as garlic1
 leeks1 turnips1 and cabbage1 the odor  
is so pronounced as to render the milk  
quite unfit for use4 ,in some states    
along the ,atlantic seaboard1 wild      
plants of this character in woodland    
pastures may be so abundant as to make  
it impossible to pasture milch animals4 
,the difficulty in such cases is due to 
absorption of the volatile principles   
into the circulation of the animal1 and 
if such feed is consumed shortly before 

milking1 the characteristic odors appear
 in the milk4 ,if consumed immediately  
after the milk is withdrawn from the    
animal1 sufficient time may elapse so   
that the peculiar odors are dissipated  
before the milk is again secreted4 ,the 
same principle applies in a lesser      
degree to the use of certain green      
fodders that are more suitable for feed1
 such as rape1 green rye1 or even       
silage4 ,silage produces a distinct1 but
 not unpleasant odor in milk1 but newly 
pastured rye often confers so strong an 
odor as to render the milk unusable4    
,where certain drugs are employed in the
 treatment of animals1 such as          
belladonna1 castor oil1 sulfur1 or      
turpentine1 the peculiar odors may      
reappear in the milk4 ,such mineral     
poisons as arsenic have been known to   
persist for a period of three weeks     
before elimination4  ,on account of the 
elimination of many drugs1 unchanged1   
from the animal in the milk1 the milk of
 any animal that is receiving medicine  

should not be used for human food4 ,when
 such milk is mixed with that of a      
number of other animals and when it is  
used by adults1 no harm is likely to    
result1 but when the dilution is not    
great and the milk is used for young    
children it may affect them through its 
content of the drug4 ,the feed may not  
only affect the quality of milk but its 
value as food4 ,one of the most         
prominent of ,american dairymen1 who has
 for many years produced milk especially
 for children's use1 has said that he   
could feed his cows so as to make ill   
every child receiving the milk4         
,absorption of odors after milking4 ,if 
milk is brought in contact with strong  
odors after being drawn from the animal1
 it will absorb them readily1 as in the 
barn1 where frequently it is exposed to 
the odor of manure and other fermenting 
organic matter4  ,it has long been a    
popular belief that milk evolves odors  
and cannot absorb them so long as it is 
warmer than the surrounding air1 but    

from experiments of one of us 7,r71 it  
has been definitely shown that the      
direct absorption of odors takes place  
much more rapidly when the milk is warm 
than when cold1 although under either   
condition1 it absorbs volatile          
substances quite rapidly4  ,the custom  
of straining the milk in the barn has   
long been deprecated as inconsistent    
with proper dairy practice1 and in the  
light of the above experiments1 an      
additional reason is evident why this   
should not be done4  ,even after milk is
 thoroughly cooled1 it may absorb odors1
 as is noted where the same is stored in
 a refrigerator with certain fruits1    
meats1 fish1 etc4  ,distinguishing      
bacterial from other taints4 ,in        
perfectly fresh milk it is relatively   
easy to distinguish between taints      
caused by the growth of bacteria and    
those attributable to direct absorption4
 ,if the taint is evident at time of    
milking1 it is in all probability due to
 character of feed consumed1 or possibly

 to medicines4 ,if1 however1 the        
intensity of the taint grows more       
pronounced as the milk becomes older1   
then it is probably due to living       
organisms which require a certain period
 of incubation before their by-products 
are most evident4  ,moreover1 if the    
difficulty is of bacterial origin1 it   
can be frequently produced in another   
lot of milk 7heated or sterilized is    
preferable7 by inoculating the same with
 some of the original milk4 ,not all    
abnormal fermentations are able1 though1
 to compete with the lactic acid        
bacteria1 and hence outbreaks of this   
sort soon die out by the                
re-establishment of more normal         
conditions4  ,factory contamination4 ,as
 the time element is of importance in   
the production of troubles due to       
bacteria1 it follows that infection of  
milk on the farm is fraught with more   
consequence than factory contamination1 
as the organisms introduced would have a
 longer period of development4          

,nevertheless1 the conditions in the    
factory are by no means to be ignored1  
as they not infrequently permit the milk
 to become seeded with highly           
undesirable types4 ,a much more rigid   
control can be exercised in the factory1
 where steam is at hand as an aid in the
 destruction of organisms4 ,in the      
cleaning of pumps and pipes1 steam is   
absolutely necessary to keep such       
apparatus in a sanitary condition4  ,the
 water supply of the factory is a matter
 of prime importance1 as water is used  
so extensively in all factory           
operations4 ,when taken from a shallow  
well1 especially if surface drainage    
from the factory is possible1 the water 
may be contaminated to such an extent as
 to introduce undesirable bacteria in   
such numbers that the normal course of  
fermentation may be changed4 ,the       
quality of the water1 aside from flavor1
 can best be determined by making a curd
 test 7p4 #ii7 which is done by adding  
some of the water to boiled milk1 and   

incubating the same4 ,if gassy          
fermentations occur1 it signifies an    
abnormal condition4 ,in deep wells1     
pumped as thoroughly as is generally the
 case with factory wells1 the germ      
content should be very low1 ranging from
 a few score to a few hundred bacteria  
per cubic centimeter at most4 ,the      
danger from ice is much less1 for the   
reason that good daily practice does not
 sanction using ice directly in contact 
with milk or cream4 ,then1 too1 water is
 largely purified in the process of     
freezing1 although if secured from a    
polluted source1 reliance should not be 
placed in this method of purification1  
for even freezing does not destroy all  
vegetating bacteria4  ,the ordinary     
house fly is an important source of     
contamination in creameries1 cheese     
factories and city milk plants4 ,they   
are of importance not only in increasing
 the number of fermentative bacteria in 
milk but they may serve to contaminate  
it with disease-producing organisms4    

,the windows of all places where milk is
 handled1 whether on the farm or        
elsewhere should be screened4  ,it      
should be kept in mind in the handling  
of milk and other dairy products that   
human food is being prepared and that   
cleanliness is desirable from every     
point of view1 and that the methods of  
handling and production should compare  
with those used in the preparation of   
foods which like milk cannot be cleaned 
when once polluted4 ,desirability1      
keeping quality1 healthfulness and the  
value of every product made from milk   
depends upon the extent and amount of   
contamination4     ,,chapter ,,iv4      
,,infection ,,of ,,milk ,,with          
,,pathogenic ,,bacteria4   ,that the    
disease-producing1 or pathogenic        
bacteria1 are able to infect milk       
supplies is shown by the fact that      
numerous epidemics of contagious disease
 have been directly traced to milk      
infection4 ,milk is generally consumed  
in a raw state1 and as a considerable   

number of this class of organisms are   
able not only to live but actually grow 
in milk1 which is such an ideal         
culture-medium for the development of   
most bacteria1 it is not surprising that
 disease processes should be traced to  
this source4 ,the organisms in milk     
capable of causing disease do not alter 
or change its physical properties       
sufficiently to enable their presence to
 be detected by a physical examination4 
,origin of pathogenic bacteria in milk4 
,disease-producing bacteria may be      
grouped1 with reference to their        
relation toward milk1 into two classes1 
depending upon the manner in which      
infection occurs3  ,class ,i4           
,disease-producing bacteria capable of  
being transmitted directly from a       
diseased animal to man through the      
medium of infected milk4  ,class ,,ii4  
,bacteria pathogenic for man but not for
 cattle1 which are capable of thriving  
in milk after it is drawn from the      
animal4  ,in the first group1 the       

disease produced by the specific        
organism must be common to both cattle  
and man4 ,the organism must live a      
parasitic life in the animal1 developing
 in the udder1 and so infect the udder4 
,it may1 of course1 happen that diseases
 toward which domestic animals alone are
 susceptible may be spread from one     
animal to another in this way without   
affecting human beings4  ,in the second 
group the bacterial species live a      
saprophytic existence1 growing in milk1 
as in any other nutrient medium1 if it  
happens to find its way therein4 ,in    
such cases1 milk indirectly serves as an
 agent in the dissemination of disease1 
by giving conditions favorable to the   
growth of the disease germ4  ,by far the
 most important of diseases that may be 
transmitted directly from animal to man 
through a milk supply is tuberculosis1  
but in addition to this1 foot and mouth 
disease 7aphthous fever in children71   
,malta fever1 and acute enteric troubles
 have also been traced to a similar     

source of infection4  ,the most         
important specific diseases that are    
disseminated through subsequent         
infection of the milk are typhoid fever1
 diphtheria1 scarlet fever1 and cholera1
 but1 of course1 the possibility exists 
that any disease germ capable of living 
and thriving in milk may be spread in   
this way4 ,in addition to these diseases
 that are caused by the introduction of 
specific organisms 7the causal organism 
of scarlet fever has not yet been       
definitely determined71 there are a     
large number of more or less illy       
defined troubles of an intestinal       
character that occur especially in      
infants and young children that are     
undoubtedly attributable to the activity
 of micro-organisms that gain access to 
milk during and subsequent to the       
milking1 and which produce changes in   
milk before or after its ingestion that 
result in the formation of toxic        
products4  ,tuberculosis4 ,this disease 
is by far the most important bacterial  

malady that affects man and beast4 ,in  
man1 it assumes a wide variety of       
phases1 ranging from consumption1       
tuberculosis of the lungs1 which is by  
far the most common type1 to scrofulous 
glands in the neck1 cold abscesses1     
hip-joint1 and bone diseases1 as well as
 affection of the bowels4 ,these various
 manifestations are all produced by the 
inroads of the specific organism1       
,bacillus tuberculosis4 ,the bovine1 as 
well as swine1 fowls1 and other         
warm-blooded animals1 are also affected 
with similar diseases4 ,in man1 the     
importance of the malady is recognized  
when it appears that fully one-seventh  
of the human race die of this scourge4  
,in cattle1 the disease is equally      
widespread1 particularly in those       
countries where live stock has been     
intensively developed4 ,in the northern 
countries of ,europe1 such as ,denmark1 
,germany1 ,england1 ,france1 and the    
,netherlands1 as well as in ,canada1 and
 this country1 this disease has been    

most widely disseminated4 ,this has been
 occasioned1 in large measure1 because  
of the exceedingly insidious nature of  
the disease in cattle1 thereby          
permitting interchange of such diseased 
stock without the disease being         
recognized4 ,tuberculosis is found more 
abundantly in this country in dairy than
 in beef stock4 ,dairy cattle are1      
however1 not more susceptible1 but the  
closer environment in which milch cattle
 are kept1 and the fact that there has  
been greater activity in the matter of  
introducing improved strains1 accounts  
for the larger percentage of affected   
animals4  ,it has been a disputed       
question for some years whether the     
organisms producing bovine and human    
tuberculosis are identical or from the  
practical standpoint1 whether the bovine
 type of disease is transmitted under   
natural conditions to man4 ,the         
bacteriologist can readily detect       
differences in appearance1 in growth of 
cultures1 and in disease-producing      

properties between the two strains4 ,of 
the two1 the bovine is much the more    
virulent when inoculated into           
experimental animals4 ,in a considerable
 number of cases1 record of accidental  
infection from cattle to man has been   
observed4 ,these have occurred in       
persons making postmortem examination on
 tuberculous animals1 and the tubercular
 nature of the wound proven by excision 
and inoculation4  ,more recently1 since 
the agitation by ,robert ,koch of       
,germany1 a number of scientific        
commissions have studied particularly   
the problem of transmission4 ,it is now 
estimated that perhaps seven per cent of
 the tuberculosis in man is of bovine   
origin4 ,this is almost wholly confined 
to children4 ,the portions of the body  
that become diseased1 when the infection
 has resulted from the use of milk1 are 
the glands of the neck and of the       
abdomen4  ,manner of infection in man4  
,in the main1 the source of the malady  
may be traced either to air infection or

 to the food1 if one disregards the     
comparatively small number of cases of  
wound infection4 ,air is frequently a   
medium by which the germ is transferred 
from one person to another4 ,the sputum 
is exceedingly rich in tubercle bacilli 
and since this material is carelessly   
distributed by tubercular people1 the   
air of the cities1 villages and public  
buildings will frequently contain       
tubercle organisms4 ,some of the        
organisms in the air find their way into
 the lungs1 there to develop and produce
 consumption4 ,the organisms in the air 
may be deposited in the nasal passages  
and throat1 and ultimately find their   
way into the tissues of the body by     
penetrating the walls of the throat or  
of the intestine4 ,it is probable that  
the tubercle bacilli thus introduced may
 find their way to the lungs and there  
develop without leaving any trace of    
their path4  ,food may also possibly    
serve as a medium of infection4 ,the    
contamination of solid food from flies  

and other sources is1 of course1 a      
possibility1 but tuberculous meat from  
cattle and swine is much more likely to 
occur1 although it must be said that the
 processes of preparing such food for   
use 7roasting1 frying1 and boiling7 are 
sufficient to destroy the vitality of   
the causal organism4 ,the fact that most
 food products of this character are now
 inspected renders this possibility less
 likely to occur4  ,unquestionably1 the 
likelihood of ingesting tubercle        
organisms is much greater with milk than
 with any other food supply1 as milk is 
consumed usually in an uncooked state1  
and as microscopic and physiologic tests
 indicate that not infrequently milk    
from tuberculous animals contains these 
organisms4  ,distribution of the disease
 in animals4 ,as practically any organ  
of the body may be affected with        
tuberculosis1 it naturally follows that 
the lesions of this disease are widely  
distributed4 ,the disease germ is       
introduced1 in the main1 through the    

lymph and not the blood system2         
consequently1 in the initial stages the 
evidence of tuberculosis is often       
comparatively slight1 and the lesion is 
restricted in its development4 ,where   
such a condition obtains1 it is known as
 closed1 in contradistinction to open   
tuberculosis1 where the diseased tissue 
is more or less broken down and is      
discharging into the circulation1 or    
elsewhere4 ,manifestly1 the danger of   
spreading not only in the affected      
animal itself1 but to the outside1 is   
much greater in the case of the open    
lesion4 ,especially is this true where  
the disease is present in the lungs or  
organs that have an exterior opening so 
that the material containing the        
organisms is discharged from the body in
 the sputum1 manure1 urine or milk4 ,the
 intestines themselves are rarely       
affected1 but the lymph glands          
associated with the intestinal tract are
 not infrequently involved4  ,infection 
of milk with tubercle bacilli4 ,in a    

small percentage of cases1 the udder    
itself becomes involved4 ,where this    
condition obtains1 one or more hard     
lumps are formed1 which slowly increase 
in size1 usually being restricted to one
 quarter of the udder4 ,sometimes the   
affected quarter may develop to an      
enormous size1 producing a hard1        
painless tumor4 ,not often does the     
affected tissue break down into pus2    
consequently1 no abnormal appearance is 
to be noted in the milk secretion until 
the disease has made very extended      
progress1 in which case the percentage  
of fat generally diminishes4 ,whenever  
the udder shows physical manifestation  
of this disease1 the milk almost        
invariably is rich in tubercle bacilli4 
,tubercle organisms may also appear in  
milk of animals in which no physical    
symptoms of the disease are to be found4
 ,this fact has been demonstrated by    
microscopic and animal experiments1 but 
it is also abundantly confirmed by the  
frequent contraction of the disease by  

calves and hogs when fed on factory     
by-products4 ,this latter class of      
animals is particularly dangerous1      
because there is no way in which the    
danger can be recognized4               
,illustration3 ,fig4 #ag4--;a           
,tuberculous ,animal4  ,the animal      
appears perfectly healthy although she  
has had the disease for five years4  ,it
 has also been proven that milk may     
become infected through the feces4 ,in  
coughing up material from the lungs and 
associated glands1 the matter is        
swallowed1 instead of expectorated1 as  
in man4 ,the organisms retain their     
vitality in the intestine1 and are      
voided in the feces4 ,under ordinary    
conditions1 the flanks and udder become 
more or less polluted with such filth1  
and the evidence is conclusive that     
infection of milk is not infrequently   
occasioned in this way4 ,the fact that  
hogs following tuberculous steers in the
 feeding lots are very likely to acquire
 the disease is explained by the        

presence of tubercle organisms in the   
manure of such animals4  ,illustration3 
,fig4 #ah4--;a ,tuberculous ,animal4    
,the last stages of generalized         
tuberculosis4 ,note the emaciated       
condition4  ,it must be kept in mind    
that many animals may be infected with  
tubercle bacilli and therefore have     
tuberculosis in the incipient stages1   
without their being able to disseminate 
the disease to others4 ,in the early    
stages1 they are bacillus-carriers      
without being necessarily dangerous at  
that particular time1 but the           
possibility always exists1 as the       
disease develops in the system1 that the
 trouble may assume a more formidable   
character1 and that slowly developing   
chronic lesions may become acute1 and   
open1 in which case1 the affected animal
 becomes a positive menace to the herd4 
,as the time when the lesions change    
from the closed to the open type and the
 animal becomes a source of danger      
cannot be determined1 the only safe way 

to do is to exclude the milk of all     
tuberculous animals from the general    
supply1 whether for direct consumption1 
or for manufacture into dairy products  
and to look upon every diseased animal  
as a menace to the herd4 ,this is       
rendered all the more necessary when the
 milk is used for the feeding of        
children1 who are relatively more       
susceptible to intestinal infection than
 the adult4 ,the early stages of the    
disease in cattle are1 however1 so      
insidious that no reliance can be placed
 upon the detection of the malady by    
physical means4 ,fortunately1 in the    
tuberculin test1 a method is at hand1   
which in a simple1 but effective manner1
 enables the disease to be distinguished
 in even the early stages1 long before  
recognition is possible in any other    
way4  ,tubercle bacilli in dairy        
products4 ,when infected milk is used   
for the preparation of butter and       
cheese1 the organisms inevitably are    
incorporated in them4 ,in the separation

 of milk a relatively large part of the 
tubercle organisms in the milk appear in
 the cream4 ,in the making of cheese    
even more of the organisms are held in  
the curd4 ,in butter and cheese1 as in  
milk1 no growth of the organism can take
 place2 however1 the vitality of the    
organism is retained for a considerable 
number of months4 ,it is not believed   
that these products are of much         
importance in the spread of tuberculosis
 in the human family1 since they are not
 consumed by children to any extent4    
,cream is to be considered as a means of
 distribution since it is often used by 
children4  ,treatment of tuberculous    
milk4 ,it is easily possible to treat   
milk or factory by-products so as to    
render them positively safe4 ,the       
process of pasteurization or            
sterilization is applicable to whole    
milk1 and when effectively done destroys
 entirely the vitality of any tubercle  
bacilli4 ,in making such exposure1 care 
should be taken to prevent the formation

 of the scalded layer1 as the resistance
 of the organism toward heat is greatly 
increased under these conditions4 ,in a 
closed receptacle1 #adj ,f4 for #ae to  
#bj minutes has been found thoroughly   
effective in destroying this organism4  
,a momentary exposure at #agf ,f4 is    
likewise sufficient4 ,this is the method
 that is almost universally used in     
,denmark in the manufacture of the      
finest butter4  ,in the treatment of    
factory by-products1 heat should also be
 employed4 ,in ,denmark1 compulsory     
pasteurization at not less than #agf ,f4
 is required4 ,this treatment prevents  
not only the dissemination of           
tuberculosis among hogs and young       
cattle1 but is equally efficacious in   
preventing the spread of foot and mouth 
disease4  ,the per cent of tuberculous  
milch cows varies widely in different   
sections of the country1 being greatest 
in the older dairy sections1 and in     
those supplying milk to the cities1 on  
account of the constant buying and      

selling of animals1 thus giving more    
frequent opportunity of introducing the 
disease into the herds4 ,throughout the 
country at large1 probably less than ten
 per cent of the cows are tuberculous1  
and it is estimated that at least one   
per cent of the diseased animals have   
tuberculous udders4 ,it has been        
suggested that the dilution of the milk 
of such animals with that of healthy    
cows would remove a great part of the   
danger from milk4 ,in the case where the
 milk of a large number of herds is     
mixed1 this may be of some importance1  
but in no case is it safe to assume that
 dilution of the milk of tuberculous    
cows is any guarantee of safety4  ,it   
has been shown that milk1 perfectly     
normal in appearance1 coming from a     
tuberculous udder could be diluted a    
million times and still produce the     
disease on inoculation into experimental
 animals4 ,in the case of swine1 the    
susceptibility is so great that a single
 feeding of infected milk1 even in a    

very dilute condition1 causes with      
certainty the production of the disease4
  ,some observers maintain that the     
contamination of the milk with the      
manure of tuberculous animals is of     
greater hygienic importance1 than that  
coming from diseased udders1 since the  
number of animals having tuberculosis of
 the lungs and intestines is far greater
 than those with diseased udders4       
,economic aspects of bovine             
tuberculosis4 ,not only is this disease 
invested with much importance because of
 its inter-relation with the human1 but 
from an economic point of view alone1 it
 is undoubtedly the greatest scourge    
that affects the dairyman4 ,its         
insidiousness makes it exceedingly      
difficult to recognize4 ,the consequence
 is that many fine herds become         
seriously involved before its presence  
is recognized4 ,in the main1 the disease
 is introduced into a herd by purchase1 
often by buying in pure-bred stock to   
improve the quality of the herd4 ,where 

the disease has been established in a   
region for some time1 there is also     
danger that unheated factory            
by-products1 as skim milk and whey1 may 
function in its spread4 ,where such     
conditions prevail1 the spread of the   
disease in the creamery district is     
exceedingly rapid4 ,when once introduced
 into a herd1 the disease sooner or     
later spreads from the originally       
affected animal to others in the herd4  
,close contact1 and close confinement in
 ill ventilated stables facilitate the  
spread of the disease1 and sooner or    
later1 other animals acquire the        
trouble4 ,this may all occur while all  
animals appear in a healthy condition4  
,the symptoms of the disease in the     
earlier stages are quite indefinite4 ,as
 the disease progresses1 the nutritive  
functions appear to be disturbed1 and   
sooner or later1 the body weight begins 
to decline1 and finally marked          
emaciation ensues4 ,accompanying this   
condition1 especially when the disease  

is in the lungs1 is a cough1 which is   
generally aggravated with active        
exercise4 ,while the run-down condition 
permits frequently of the detection of  
the disease in the advanced stages1 it  
is wholly impossible with any accuracy  
to diagnose the trouble in the incipient
 stages4 ,it is at this stage that the  
tuberculin test comes to the aid of the 
stockman4  ,tuberculin test4 ,this test 
is made by the injecting beneath the    
skin of the animal a small quantity     
7about #b c4 c47 of tuberculin1 and     
noting the temperature of the animal1   
before and after the injection4         
,tuberculin1 a product of the growth of 
the tubercle bacillus1 when injected    
into the body causes a marked rise in   
temperature1 in the case of an animal   
affected with the disease1 and no such  
elevation in the case of a healthy      
animal4 ,the process of preparing       
tuberculin makes it absolutely free from
 danger1 so far as liability of         
producing the disease1 or in any way    

injuring the animal1 is concerned4 ,fig4
 #ai shows the temperature range of both
 reacting and non-reacting animals4     
,while the test is not absolutely       
infallible1 it is so far superior to any
 and all other methods of diagnosis that
 it should take precedence over them4   
,miscellaneous diseases4 ,there are a   
number of diseases that affect both     
human beings and cattle1 the causal     
organisms of which may be transmitted   
through the milk4 ,foot and mouth       
disease is one wide spread in ,european 
countries but which has not yet gained a
 permanent foothold in this country4    
,the ingestion of the milk1 which always
 contains the causal organism1 produces 
the disease in both humans and cattle4  
,in the human the disease is very       
similar to that in cattle2 it may end in
 death4 ,vesicles are produced in the   
mouth1 on the lips1 nose and fingers4   
,the causal organism1 which has not yet 
been demonstrated1 may occur in butter  
or cheese4 ,it is easily destroyed by   

pasteurizing the milk4  ,illustration3  
,fig4 #ai4--,temperature ,curves4  #a1  
the temperature curve of a healthy      
animal after injection with tuberculin2 
#b and #c1 the temperature curves of    
tuberculous animals after injection with
 tuberculin4 7,after ,moore47  ,anthrax1
 actinomycosis 7lumpy jaw71 rabies1 and 
malta fever are diseases the organisms  
of which have been found in the milk of 
affected animals4 ,in case of the first 
three1 while the possibility exists of  
the infection of human beings by milk1  
it is improbable that such infection    
does normally occur4 ,malta fever is    
becoming an important disease in        
portions of southern ,europe4 ,it is    
produced in man by the use of milk of   
goats suffering from the disease4  ,the 
organism causing contagious abortion in 
cattle is known to be present in the    
milk of the infected animal at the time 
of its withdrawal from the udder4 ,it is
 not probable that the organism is of   
any sanitary significance as far as man 

is concerned4 ,it has been shown that   
the organism is able to produce a       
disease in guinea pigs on artificial    
inoculation that is very similar1 so far
 as the lesions are concerned1 to       
tuberculosis4 ,it is also probable that 
the by-products of creameries and cheese
 factories may serve to spread the      
disease from one herd to another4       
,inflammation of the udder 7garget7 is a
 frequent trouble in every herd4 ,it is 
marked by the swelling of one or more   
quarters1 by the appearance of fever and
 changes in the appearance and          
composition of the milk4 ,the           
inflammation may be caused by cold or   
injury1 or by the invasion of the udder 
with pus-forming bacteria4 ,in the first
 case the trouble is not likely to      
persist for any length of time1 and does
 not spread to other members of the     
herd4 ,the milk may be more or less     
stringy1 and may show a slimy flocculent
 sediment4 ,it cannot be asserted that  
such milk is harmful to man but it      

should be rejected on general sanitary  
grounds1 and because it cannot always be
 differentiated from that coming from an
 udder in which the inflammation is     
produced by bacteria4  ,inflammation    
caused by the invasion of the udder with
 specific bacteria is usually of greater
 severity1 the entire gland often       
becoming involved4 ,the secretion of    
milk may cease and the function of the  
diseased quarters may never be restored4
 ,the milk in the less severe cases may 
not be abnormal in appearance1 but with 
increasing severity1 the nature of the  
milk changes1 until it may be a watery  
liquid4 ,the milk of any animal         
suffering from any form of garget should
 be rejected1 as it may cause trouble1  
especially in children4 ,there is some  
reason to believe that organisms coming 
from cases of garget have been          
responsible for the extensive outbreaks 
of septic sore throat that have occurred
 in some parts of the country4  ,the    
milk of animals suffering from          

indigestion1 diarrhea1 abscesses on any 
part of the body1 as from those which   
have retained the afterbirth should be  
likewise rejected4 ,in short only the   
milk of healthy animals should be used  
for human food2 that from any animal    
suffering from any disease or which is  
receiving medical treatment should not  
be so used4  ,typhoid fever4 ,the most  
important disease germ1 distributed     
through the medium of milk1 that is     
unable to produce a diseased condition  
in the cow is the organism of typhoid   
fever4 ,this malady is an intestinal    
affliction of man1 and the germ causing 
the same is found abundantly in the     
dejecta1 both solid and liquid1 as well 
as in the blood in certain stages of the
 disease4 ,while the causal organism    
does not leave the body through the     
expired air1 it is found abundantly in  
both the urine and feces4 ,therefore1   
the dejecta1 and any articles that may  
be soiled with the same become a        
positive menace4  ,many different       

methods of transmitting the contagion   
exist1 such as water1 food infected in  
various ways1 contact with infected     
persons1 and through the medium of milk4
 ,milk is not so frequently the cause of
 dissemination as the other factors1 but
 where milk supplies become             
contaminated1 epidemics of considerable 
magnitude are wont to occur4 ,the danger
 from milk is also aggravated by the    
fact that the typhoid bacillus is       
capable of withstanding considerable    
amounts of acid1 and consequently finds1
 even in raw milk containing the normal 
lactic acid bacteria1 conditions        
favorable for its growth4 ,in a         
considerable percentage of cases1 the   
disease is not sufficiently severe to   
cause the patient to take to his bed4   
,these so-called walking typhoid cases  
are particularly dangerous1 because they
 serve to spread the disease organism   
more widely4  ,a very considerable      
proportion of the people that recover   
from typhoid fever still continue to    

harbor the typhoid bacillus in their    
urinary and gall bladders4 ,this        
condition may obtain for years1 and     
since such individuals are in perfect   
health and are ignorant of their own    
condition1 and since they give off the  
organisms more or less constantly1 they 
are often the cause of extensive milk   
borne epidemics4 ,such persons are known
 as typhoid carriers and constitute one 
of the gravest problems the public      
official has to contend with in his     
struggle to prevent the spread of       
typhoid fever4  ,where outbreaks are    
caused by milk1 they can readily be     
traced by means of the milk route1 as   
there are always a sufficient number of 
susceptible persons1 so that outbreaks  
of epidemic proportions develop4 ,in the
 ,stamford1 ,conn41 outbreak in #ahie1  
#chf cases developed on one milk route4 
,in this case it was shown that the     
carrying cans were thoroughly washed1   
but were later rinsed out with cold     
water from a polluted shallow well4     

,the mode of infection of milk varies1  
but in general1 the original pollution  
is occasioned by the use of infected    
water in washing the utensils1 or a case
 of walking typhoid or bacillus carrier1
 who directly infects the milk4 ,in case
 of sickness in rural families1 some    
member of the household may serve in the
 dual capacity of nurse and milkmaid1   
thus establishing the necessary         
connection4 ,busey and ,kober report    
twenty-one outbreaks1 in which dairy    
employees also acted in the capacity of 
nurses4 ,the fact that the urine of a   
convalescent may retain the typhoid germ
 in large numbers for some weeks renders
 the danger from this source in reality 
greater than from feces1 as1 naturally1 
much less care is exercised in the      
disposition of the urine4  ,the house   
fly is now regarded as one of the       
important means of spreading typhoid    
fever1 indeed it is often called the    
typhoid fly4 ,the infectious material   
deposited in an open vault may serve as 

a source from which the fly carries the 
organisms to milk and other foods in the
 house or elsewhere4 ,the protection of 
vaults and the screening of every place 
where human food is handled or prepared 
is the only protection4  ,it should be  
emphasized that in the case of the      
tubercle organism1 no growth ever occurs
 in milk1 but with the typhoid bacillus 
growth is possible4 ,it thus needs but  
the contamination of the milk with the  
smallest particle of material containing
 them to seed the milk4 ,by the time it 
is consumed it may contain myriads of   
the disease-producing organisms4        
,diphtheria4 ,this is a highly          
infectious disease1 affecting children  
primarily and is characterized by the   
formation of membranous exudates in the 
throat and air passages1 which are      
teeming with the causal organism1 the   
diphtheria bacillus4 ,this organism is  
capable of forming highly toxic         
products1 and it is to the effect of    
these poisons that its fatal result is  

generally due4 ,the organism is thrown  
out from the body1 in the main1 through 
the mouth1 the surroundings of the      
patient being infected directly from the
 air1 and indirectly1 by contact with   
polluted hands1 lips1 etc4 ,thus1 the   
germ deposited from the lips of a case  
of the disease1 on the common drinking  
cup1 slate1 lead pencils1 toys1 and the 
like1 may easily pass from child to     
child4 ,not infrequently1 the causal    
organism persists in the throat long    
after all evidence of membranous growth 
has subsided1 and so the child itself   
may act as a bacillus carrier4  ,not so 
many epidemics of diphtheria as of      
typhoid have been traced to milk1 but   
the evidence is sufficient to indict    
milk as a disseminator of contagion4 ,in
 several cases1 the diphtheria germ has 
actually been isolated from infected    
milk supplies4 ,actual growth of the    
diphtheria germ is said to take place in
 raw milk more rapidly than in          
sterilized4  ,scarlet fever4 ,while the 

germ of scarlet fever has not yet been  
isolated1 and therefore its life history
 in relation to milk cannot be depicted 
so accurately1 yet milk-borne epidemics 
of this disease are sufficiently        
abundant to leave no doubt but that this
 food medium may sometimes serve as a   
means of disseminating such troubles4   
,infection of the milk doubtless comes  
in the case of this disease from direct 
contact with a person suffering from the
 malady4  ,cholera4 ,while this disease 
is of no practical importance in        
,america1 owing to its relative         
infrequency1 yet outbreaks of cholera   
have been traced to milk1 in spite of   
the fact that the causal organism is    
more sensitive to the action of acids   
than most disease-producing bacteria4   
,in several outbreaks in ,india1 milk   
has been the medium through which the   
disease was spread4 ,generally1         
infection of the milk has been traced to
 the use of polluted water4  ,children's
 diseases4 ,an exceedingly high         

mortality exists among infants and young
 children in the more congested centers1
 especially during the summer months4   
,in the main1 the cause of these        
troubles is due to intestinal           
disturbances1 and unquestionably1 the   
character of the food enters largely    
into the problem4 ,as milk constitutes  
such a large proportion of the diet of  
the young1 and is so susceptible to     
bacterial invasion1 it would appear     
probable that much of the trouble of    
this character is due to the condition  
of this food supply4 ,this is rendered  
more probable when it is remembered that
 bottle-fed infants suffer a much higher
 mortality than breast-fed children1 due
 probably to the fact that the          
lengthened period between the time the  
milk is drawn and consumed permits of   
abundant bacterial growth4 ,much        
carelessness also prevails among the    
poor in cities1 relative to the care of 
utensils used in feeding children4      
,nursing bottles often serve to infect  

the milk4 ,where milk is pasteurized1 or
 properly heated1 it has been found that
 the mortality rate has been greatly    
reduced1 thus indicating that the       
condition of the milk was directly      
responsible for the death rate4 ,in     
fact1 the mortality from these          
indefinite intestinal troubles probably 
exceeds that from all of the specific   
infectious diseases combined4 ,improved 
care in handling this sensitive food    
supply will do much to better conditions
 in this direction4  ,ptomaine          
poisoning4 ,acute poisoning affecting   
adults as well as children1 not         
infrequently occurs from the use of     
foods of various kinds4 ,cases of       
poisoning arising from the use of shell 
fish1 canned meats1 ice cream1 cheese1  
and other dairy products1 are from time 
to time reported4 ,these troubles are   
due to the production of toxic          
compounds1 in the main1 probably caused 
by bacterial decompositions4 ,often such
 troubles may affect a number of        

persons1 as at banquets and such        
gatherings1 thereby giving the semblance
 of an epidemic4 ,while such troubles   
are doubtless to be ascribed to         
bacterial activity1 they are not        
transmissible from person to person4    
,in the case of troubles arising from   
ice cream and such confections1 the     
probable cause is due to the storage of 
milk or cream under refrigerator        
conditions1 where germ growth can go on 
in the product1 and yet the temperature 
be sufficiently low to prevent the usual
 acid fermentations4     ,,chapter ,v4  
,,fermentations ,,of ,,milk4   ,milk1   
under normal conditions1 is always      
contaminated with bacteria coming from  
the most varied sources4 ,if it is      
produced under clean conditions1 the    
number of bacteria will be small1 but in
 any case1 the number of kinds of       
bacteria that find their way into milk  
will be large4 ,many of them find in    
milk at ordinary temperatures suitable  
conditions for growth2 they use a       

portion of some of the constituents of  
the milk as food1 producing certain     
other compounds that are known as       
by-products4 ,these by-products impart  
to milk a taste and odor that is not    
found in fresh milk4 ,the effect of the 
action of bacteria may also be made     
evident by the change in the appearance 
of the milk4 ,when these various changes
 become evident to the senses1 either by
 taste1 smell or sight1 the milk usually
 is so modified as to be unfit for many 
ordinary purposes4 ,the preservation of 
milk1 a subject to be treated later1 is 
a study of the ways of preventing or    
retarding the growth of bacteria in     
milk1 and thus delaying the time when   
evidences of their action first become  
apparent4  ,each class of bacteria      
produces more or less specific changes  
in the milk as a result of their growth4
 ,certain bacteria are of the greatest  
benefit to the butter and cheese maker1 
while others are distinctly harmful to  
the manufacturer of dairy products4 ,the

 changes produced by the different      
bacteria are called fermentations of    
milk1 each being most commonly named    
from the most important by-product      
formed4  ,acid fermentation of milk4    
,fresh milk has a sweet taste and little
 or no odor1 but if it is allowed to    
stand at ordinary temperatures1 it      
sours2 the taste is no longer sweet     
because the sweetness of the sugar of   
the milk is masked by the acid produced 
from the decomposition of a portion of  
the sugar by the bacteria4 ,the change  
in odor and taste of milk is apparent   
long before the appearance is altered   
and increases in intensity as the       
acid-fermentation progresses4 ,the first
 alteration in appearance is most       
usually one of consistency2 the liquid  
milk is transformed into a semi-solid   
mass4 ,the terms curdling and sour are  
usually synonymous4 ,milk is1 however1  
often said to be sour as soon as the    
acid fermentation has progressed to a   
point where it is evident to taste or   

smell4 ,this process of souring1 or the 
acid fermentation is so common a change 
that raw milk which does not show this  
type of fermentation is looked upon with
 suspicion1 and1 usually1 justly so4    
,the process in the past was thought to 
be something inherent in the milk1 a    
natural and inevitable change4 ,it is   
now known that this is not so1 but that 
it is due to certain kinds of bacteria1 
and that if these are prevented from    
getting into milk1 it will not sour1 but
 will undergo some other less desirable 
type of decomposition4  ,the            
acid-forming bacteria comprise but a    
very small part of the total number of  
organisms that find their way into the  
milk during its production on the farm1 
yet in sour milk scarcely any other     
kinds of bacteria can be found4 ,at     
ordinary air temperatures1 the          
acid-forming bacteria grow more rapidly 
in milk than do any other forms1 and the
 acid produced by them renders the milk 
an unfavorable medium for the growth of 

other bacteria4 ,this is the reason why 
milk practically always undergoes the   
acid fermentation1 although it is       
contaminated with a host of other kinds 
of bacteria4 ,if a mixture of seeds is  
sown on low wet ground1 certain kinds   
will grow best2 if the same mixture is  
sown on drier land1 other types will    
find most favorable conditions for      
growth1 and the plants which appeared on
 the low land will not appear4 ,the same
 condition is found in milk where the   
environment is most favorable for the   
acid-forming bacteria4  ,amount of acid 
formed in milk4 ,in this country the    
acidity of milk is expressed as so many 
per cent of lactic acid4 ,a milk that   
shows an acidity of one per cent should1
 theoretically1 contain one pound of    
lactic acid in each one hundred pounds  
of milk4 ,the acid determined does not  
actually represent lactic acid1 as there
 are other substances in milk which act 
as acids1 with the reagents used in the 
present methods of determining the      

acidity of milk4 ,for instance1         
perfectly fresh milk has an apparent    
acidity of #j4ac to #j4ah per cent1     
although no fermentation has occurred4  
,other acids than lactic are formed in  
the acid fermentation1 but the entire   
acid content is referred to as lactic   
when speaking of the acidity of milk4   
,when the developing acidity of milk    
reaches #j4be to #j4c per cent1 a sour  
taste becomes evident and the milk will 
curdle on heating4 ,when the acidity    
increases to #j4f to #j4g per cent1 the 
milk curdles at ordinary temperatures4  
,the acidity continues1 however1 to     
increase until it reaches about #a per  
cent1 which is the maximum amount that  
will be produced in milk by the ordinary
 acid-forming bacteria4 ,milk contains  
about #d per cent of milk sugar1 all of 
which is fermentable4 ,if this were all 
decomposed by bacteria1 the acidity of  
the milk would actually exceed #d per   
cent4 ,it is thus evident that the      
reason why more acid is not formed in   

milk is not because of any lack of      
sugar4 ,the bacteria1 like all other    
kinds of living things1 are injured by  
their own by-products1 unless these are 
constantly removed in some way2 in milk 
the bacteria cannot escape the action of
 the acid which they themselves have    
formed1 consequently growth ceases4 ,the
 amount of acid formed is dependent on  
the kind of bacteria present and on the 
composition of the milk4 ,certain       
bacteria will not produce enough acid to
 cause the curdling of the milk2 still  
others will form #b or even #c per cent4
 ,these types1 however1 do not play any 
important part in the spontaneous       
souring of milk4  ,in milk the acid     
first formed combines with the ash      
constituents and the casein to form     
salts which do not seriously affect the 
growth of the bacteria4 ,ultimately1 the
 limit of the ash and casein to take up 
acid is reached1 and free lactic acid   
which is harmful to bacterial growth    
appears4 ,if the content of casein and  

ash constituents is high1 a higher      
degree of acidity will be reached than  
in a milk with a lower content4 ,if a   
large part of the volume of the milk is 
made up of a compound that has no role  
whatever in the acid fermentation1 such 
as the butter fat in cream1 the amount  
of acid formed per unit volume of milk  
will be reduced1 since in determining   
the acidity1 a definite volume of milk  
is taken1 and the acidity is expressed1 
as such a per cent of this amount4      
,types of acid-forming bacteria4 ,when  
substances undergo decomposition1 it is 
a common belief that compounds offensive
 to the odor and taste are formed2 but  
such is not necessarily the case4 ,the  
products of the decomposition may be as 
agreeable and as harmless as the        
compounds decomposed4 ,whether the      
decomposition products of any substance 
are offensive or not is dependent on the
 kinds of micro-organisms acting on it4 
,there are forms of acid-producing      
bacteria that change milk in odor1      

taste1 and appearance1 yet the sour milk
 is not offensive in any sense of the   
word4 ,other bacteria also sour the     
milk1 but produce offensive odors and a 
disagreeable taste4 ,thus1 the          
acid-forming bacteria may be divided    
into two main groups1 which may be      
designated as desirable and undesirable4
 ,this division is of importance to the 
butter and cheese maker and to the      
consumer of milk4  ,desirable           
acid-forming bacteria4 ,if milk is      
produced under clean conditions1 it is  
not likely to have a disagreeable odor  
or taste at any time1 even when it is   
sour2 rather the taste is agreeable like
 that of good butter milk4 ,the curd is 
perfectly homogeneous1 showing no holes 
or rents1 due to the development of gas1
 and there is but little tendency for   
the whey to be expressed from the curd4 
,this type of fermentation is largely   
produced by the group of bacteria to    
which has been given the name1 ,bacillus
 lactis acidi4  ,the main by-product of 

this group of bacteria is lactic acid2  
small amounts of acetic acid and        
alcohol1 with traces of other compounds1
 are also formed4 ,the agreeable odor   
and to some extent the flavor of milk   
fermented by these bacteria is due to   
other by-products than lactic acid1 for 
this has no odor and only a sour taste4 
,the acid fermentation of milk is often 
called the lactic acid fermentation4 ,in
 reality only the fermentation produced 
by the desirable group in which lactic  
acid is the most evident by-product     
should be thus called4  ,illustration3  
,fig4 #bj4--;,different ,types of       
,curds4  ,on the left a solid1          
homogeneous curd produced by desirable  
bacteria2 on the right1 the curd        
produced by harmful bacteria4 ,note the 
gas holes and free whey4  ,the bacteria 
of this group may enter the milk from   
the dust coming from the coat of the    
cow4 ,they are also found in the barn   
dust and on cultivated plants4 ,under   
ordinary farm conditions1 the larger    

part of those found in milk come        
directly from the utensils4 ,if the milk
 is drawn under extremely clean         
conditions and care is taken to         
sterilize the utensils1 but few         
acid-forming bacteria of any kind will  
enter the milk2 under such conditions   
most of the acid-forming bacteria will  
belong to the group in question4 ,they  
find1 however1 such favorable conditions
 for growth in milk that they develop   
more rapidly than most other types with 
which milk becomes seeded2 consequently 
under normal conditions1 they gain the  
ascendency and so control the type of   
fermentation4  ,the desirable type of   
acid-forming bacteria do not form       
spores2 hence1 are easily killed by     
heating the milk4 ,they can grow in the 
presence or in the absence of free      
oxygen4 ,in the bottom of a can of milk 
or in the middle of a cheese1 there is  
no air1 yet these bacteria grow as well 
under these conditions1 as in milk      
exposed to the air4 ,the range of       

temperature for growth varies from #ej  
to #ajj ,f4 but development is most     
rapid at #ij to #ie ,f4 and about #a per
 cent of acid is formed4  ,another group
 of bacteria which may be classed among 
the desirable acid-forming organisms is 
constantly found in milk4 ,they have    
little to do with the ordinary acid     
fermentation as they grow very slowly at
 ordinary temperatures4 ,if a sample of 
raw milk is placed at the temperature of
 the animal body1 the acidity will reach
 #a per cent in a few hours4 ,thereafter
 the acidity will increase slowly and   
may reach three per cent or above4 ,the 
continued increase in acid is due to the
 growth of long rods of the ,bacillus   
,bulgaricus type1 which apparently enter
 the milk with the fecal matter4 ,the   
nature of the change produced by them in
 milk is very similar to that caused by 
,bact4 lactis acidi in that lactic acid 
is the chief product2 no gas is produced
 and hence the curd is uniform in       
appearance4 ,temperatures from #ajj to  

#aaj ,f4 favor their development4       
,organisms belonging to this group are  
used in the preparation of the fermented
 milks now so widely sold in the cities4
  ,these desirable1 acid-forming        
bacteria are of the greatest service in 
every branch of the dairy industry1     
whether in butter or in cheese making1  
or in the sale of milk in the city4 ,the
 dairy industry is dependent upon       
fermentative activity1 as much as the   
manufacture of beer or wine1 and the    
main basis of this is the acid          
fermentation of the milk by these       
desirable types of bacteria4  ,although 
milk contains a large amount of         
nitrogenous substances 7casein and      
albumen71 it does not undergo putrid    
decomposition1 as do meat and eggs1 not 
because it is not fitted for the growth 
of the bacteria causing that type of    
change1 but because the acid formed in  
it stops the growth of the putrefactive 
bacteria4 ,if a sample of milk is placed
 in a stoppered bottle1 it will have    

much the same taste and odor at the end 
of several months as at the end of a few
 days4 ,the acid acts as a preservative1
 like the vinegar in pickles1 or the    
acid in silage and in sauerkraut4 ,meat 
placed in a stoppered bottle which is   
then filled with milk will be preserved4
  ,the products formed in the           
decomposition of meat and eggs are not  
only offensive but may also be injurious
 to the health of the consumer4 ,milk   
that has been fermented by the desirable
 kinds of acid-forming bacteria is not  
harmful4 ,it is consumed in a variety of
 forms 7buttermilk1 cottage cheese7 as a
 common article of food and its use is  
rapidly increasing4 ,the preparation of 
the pure culture buttermilks or         
artificially soured milks that are now  
so frequently recommended for digestive 
troubles rests upon an acid fermentation
 of this type4  ,undesirable            
acid-forming bacteria4 ,other types of  
bacteria capable of forming substances  
that impart to milk an offensive odor   

and a disagreeable taste not            
infrequently appear instead of the      
desirable group4 ,instead of producing  
from the sugar of milk large quantities 
of lactic acid1 these types generate    
other acids1 such as acetic and formic1 
which impart a sharp taste to the milk4 
,besides the acids the bacteria of this 
group form gases from the sugar of the  
milk4 ,some produce small amounts of    
gas2 others so much that the curd will  
be spongy and will float on the surface 
of the whey4 ,the fermentation caused by
 them is often called a gassy           
fermentation and is dreaded by butter   
and cheese makers since the gas is      
indicative of bad flavors that will     
appear in the product4 ,gas may also be 
produced in other types of fermentations
 to be discussed later4  ,this class of 
bacteria enters the milk with the dust1 
dirt1 and manure1 in which materials    
they are especially abundant4 ,no spores
 are formed2 hence they are easily      
killed by heating the milk4 ,they grow  

both in the presence and in the absence 
of free oxygen4 ,high temperatures favor
 their growth1 most rapid development   
taking place at #ajj to #ajc ,f4        
,spontaneous fermentation of milk4 ,the 
normal souring of milk is due to a      
mixture of these two groups of bacteria4
 ,the relative proportions existing     
between the two in any sample of milk is
 dependent on a number of factors1 most 
important of which is the degree of     
cleanliness exercised in the production 
of the milk4 ,where careless conditions 
obtain under which dust and manure      
particles find their way into milk1 it  
becomes more abundantly seeded with     
gas-generating bacteria1 and            
consequently1 the type of fermentation  
is undesirable4 ,if1 however1 the milk  
is drawn into clean utensils and care is
 taken to exclude dirt1 the pure lactic 
acid types are able to control the      
character of the changes produced1 and a
 clean1 pleasant tasting liquid results4
 ,it will be seen that things are well  

arranged by nature2 one of the most     
important food products undergoes a type
 of decomposition that is not offensive 
and when produced under clean           
conditions1 the sour milk is as         
healthful a food as is the fresh        
product4 ,thus there is every reason for
 cleanliness in the production of milk1 
for cleanliness' sake and because clean 
milk means better products1 and greater 
returns to everyone1 producer and       
dealer4  ,there are other kinds of      
acid-forming bacteria in milk but they  
are of small importance compared with   
those just discussed4 ,some of the      
bacteria derived from the inside of the 
udder of the cow form acid1 but these   
forms grow very slowly in milk at       
ordinary temperatures1 and have no      
influence on the keeping quality4       
,illustration3 ,fig4 #ba4--;,different  
,types of ,curds4  ,the flask on the    
left shows the soft curd produced by the
 bacteria that curdle the milk without  
the production of acid4 ,the flask on   

the right shows the gassy curd formed by
 butyric acid bacteria in heated milk4  
,sweet curdling fermentation of milk4   
,samples of milk are sometimes found    
that are curdled1 but which do not taste
 sour1 or have the normal odor of sour  
milk4 ,the curd is usually soft and the 
taste bitter4 ,it is evident that the   
curdling cannot be due to the same      
factors as in the normal souring of     
milk4 ,such a change is similar to the  
action of rennet which is used to curdle
 the milk in cheese making4 ,this       
ferment will curdle perfectly sweet     
milk1 producing a curd that looks like  
that formed in the acid fermentation of 
milk4 ,the cause of these sweet curdling
 milks1 which appear from time to time1 
is due to the introduction of certain   
bacteria which have the power of        
secreting an enzyme resembling that     
found in rennet4 ,in such cases the     
milks curdle prematurely especially when
 warmed4 ,the curd may gradually        
disappear1 for the bacteria also produce

 another enzyme that digests the curd1  
and thus renders it soluble4 ,when this 
advanced phase becomes evident1 it is   
often called the digestive fermentation 
of milk4 ,this change is produced       
largely by putrefactive bacteria of     
various kinds that find their way into  
milk with dust and dirt4 ,many of them  
are spore formers2 hence1 are not killed
 when milk is heated1 as in             
pasteurization1 while the acid-formers  
are destroyed4 ,pasteurized milk is thus
 likely to undergo the sweet-curdling   
fermentation1 if it is kept for any     
length of time4 ,raw milk rarely        
undergoes this type of decomposition1   
since the rennet-forming bacteria under 
ordinary conditions are unable to       
develop in competition with the         
acid-forming bacteria4  ,butyric acid   
fermentation of milk4 ,a fermentation   
that is much less frequently noted than 
the two previously discussed is known as
 the butyric fermentation1 since butyric
 acid is the principal by-product4 ,the 

causal bacteria cannot compete with the 
ordinary acid-forming bacteria in raw   
milk2 hence it is most frequently noted 
in pasteurized milk1 since the organisms
 produce spores and are not killed by   
the heating4 ,pasteurized milk under the
 action of the butyric acid bacteria    
undergoes a gassy fermentation1         
developing a pronounced acidity and the 
disagreeable odor of butyric acid1 which
 resembles that of rancid butter4 ,the  
butyric acid bacteria are anaerobic1 and
 thus can grow in butter and cheese away
 from the air4  ,slimy or ropy          
fermentation of milk4 ,a slimy or ropy  
condition of milk is frequently noted on
 the farm and in the dairy4 ,several    
causes for this abnormal condition      
exist4 ,sometimes the milk may be slimy 
when milked from the cow4 ,this occurs  
most frequently in the case of          
inflammation of the udder which may or  
may not be due to bacteria4 ,the direct 
cause of the abnormal condition in milk 
is the presence of fibrin and white     

corpuscles from the blood which form    
masses of slimy material2 in such cases 
the trouble does not increase in        
intensity with age1 nor can it be       
propogated by transference to another   
sample of fresh milk4  ,illustration3   
,fig4 #bb4--,slimy ,milk4  ,it does not 
mix with water when poured into it4     
,another type of slimy milk is produced 
by the growth of certain types of       
bacteria which enter the milk after it  
is drawn from the udder4 ,these may come
 from various sources4 ,the bacteria    
concerned belong to two groups3 7#a7    
those that grow best in the air and do  
not form acid2 7#b7 those that grow in  
the absence of air1 throughout the      
entire mass of milk and which form acid4
 ,the slimy condition is noted in the   
milk only after the milk has been stored
 for some time2 it usually increases    
with the age of the milk and can be     
produced in a second sample by          
transferring a little of the slimy milk 
to it4  ,the fermentation produced by   

the aerobic bacteria is most often met  
in bottled milk and cream during the    
warmer times of the year4 ,on account of
 their relation to oxygen1 the growth is
 confined to the surface of the milk and
 only the upper layer becomes slimy2    
thus when the cream is removed1 the     
abnormal condition is noted4 ,the       
sliminess is due to the mass of         
bacterial growth rather than to the     
production of any specific substance in 
the milk4 ,this trouble may be of       
considerable economic importance to the 
dealer1 as such abnormal milk is        
objectionable for ordinary use1 but as  
far as is known1 it is incapable of     
affecting the health of the consumer4   
,in numerous outbreaks of this trouble  
the source of contamination has been    
traced to infection from well water or a
 stream1 as the organisms causing the   
trouble are found naturally in water4   
,keeping the milk in a tank in the pump 
house sometimes permits of troubles of  
this sort1 the water used for cooling   

giving opportunity for contamination4   
,cattle wading in a stream sometimes    
pollute their udders and so indirectly  
infect the milk4 ,such outbreaks rarely 
persist for any considerable length of  
time as the common acid organisms soon  
regain the ascendency4  ,creameries and 
cheese factories are sometimes troubled 
with sliminess in starters4 ,this seems 
to be due to some change which the      
ordinary lactic acid bacteria undergo on
 long propagation rather than to        
contamination of the starter4 ,there    
are1 however1 types of acid-producing   
bacteria that are able to form specific 
substances in milk that are slimy in    
character4 ,two of these forms of slimy 
milk are of economic importance4 ,the   
slimy whey 7lange ,wei7 of ,holland is  
added to milk in the manufacture of     
,edam cheese1 apparently serving the    
same purpose as the addition of the pure
 culture starter in cheddar cheese      
making4 ,in ,norway1 a sour1 slimy milk 
7taettemjolk7 is used as food4 ,it is   

produced by the addition of some        
previously fermented milk4 ,this        
beverage is also used in some of the    
,norwegian settlements of ,wisconsin1   
the original seed having been brought   
from ,norway1 and the bacteria          
maintained by constant propagation from 
one sample of milk to another4 ,the milk
 has the odor and taste of butter milk1 
but is not especially appetizing in     
appearance to any one not accustomed to 
it2 it is1 however1 as harmless to      
health as is any other form of sour     
milk4 ,it is not known that any of these
 forms of slimy milk are distinctly     
harmful to the quality of butter or     
cheese4  ,alcoholic fermentation of     
milk4 ,the bacteria as a class are      
incapable of producing alcohol in       
appreciable amounts4 ,the alcoholic     
beverages1 beer1 wine1 and cider1 are   
produced by the growth of yeast1 in such
 sugar containing liquids as fruit      
juices1 extracts of grains1 etc4 ,the   
common types of yeasts are incapable of 

acting on milk sugar1 but they can      
ferment glucose1 maltose1 and cane      
sugar1 forming equal amounts of alcohol 
and carbonic acid gas1 which causes the 
effervescence of fermented and          
carbonated drinks4 ,there are1 however1 
some types of yeasts found in milk and  
its products that are able to ferment   
milk sugar4  ,all yeasts grow best in an
 acid medium1 hence those fermenting    
milk sugar find suitable conditions for 
growth in sour milk or whey4 ,they may  
at times become of economic importance  
in the cheese industry1 because of the  
contamination of the milk with large    
numbers of them4 ,the arrangement of the
 whey vat is often such that it cannot  
be completely emptied and cleaned2 the  
sour whey thus presents favorable       
conditions for the growth of the        
lactose-fermenting yeasts4 ,the return  
of the whey to the farm in the milk can 
that is often imperfectly cleaned may   
serve to contaminate the milk with the  
yeast4 ,in the making of ,swiss cheese  

the whey is often so handled as to favor
 especially the growth of such yeasts1  
and since this type of cheese is        
prepared from sweet milk1 the           
competition between the yeast and the   
acid-forming bacteria is not so sharp as
 in the making of cheddar cheese4 ,the  
writers have found several instances    
where considerable loss was occasioned  
in the ,swiss cheese industry through   
the development of gassy cheese due to  
this type of fermentation4  ,the yeasty 
or alcoholic fermentation may also be of
 importance in butter making4 ,in many  
sections of the country the milk is     
separated on the farm and the cream is  
forwarded to the creamery at more or    
less infrequent intervals4 ,it becomes  
sour and if it has become contaminated  
with yeasts1 they will find favorable   
conditions for growth in the acid       
medium4 ,a large amount of carbon       
dioxide gas is produced4 ,cans of       
gathered cream often foam to such an    
extent as to run over1 and in some cases

 actual explosions have occurred on     
account of the great pressure caused by 
the gas4  ,bitter fermentation of milk4 
,bitterness in milk may be due to       
bacteria that enter the milk after it is
 drawn from the cow1 or it may be caused
 by the feed consumed by the animal4 ,it
 has been previously shown that certain 
specific substances contained in the    
food may be absorbed and reappear in the
 milk4 ,if the animal eats ragweed1     
lupines1 or other plants containing     
bitter substances1 the milk is likely to
 have a bitter taste1 which will be     
noticeable at the time the milk is      
drawn4 ,the milk of cows at certain     
advanced stages of lactation may show a 
bitter taste1 due to a change in the ash
 constituents of the milk in which the  
lime salts are largely replaced by salts
 of sodium4  ,there are many bacteria   
that will impart to milk a bitter taste4
 ,milk that has undergone the           
sweet-curdling fermentation is likely to
 be bitter1 as is the ease with         

pasteurized milk4 ,some of the          
acid-forming bacteria are able to       
develop a bitter principle1 the milk    
retaining a pleasant odor and having the
 normal amount of acid1 while the taste 
is intensely bitter4 ,one of the authors
 7,h7 found in the case of a ,wisconsin 
brick cheese factory1 that the usual    
acid organism was almost wholly replaced
 by a bitter type4  ,storage of milk at 
very low temperatures is conducive to   
the appearance of a bitter taste in     
milk1 the explanation in this case being
 that the acid-forming bacteria are     
unable to grow at a low temperature1    
while some of the putrefactive forms can
 multiply and develop these astringent  
or bitter by-products4  ,miscellaneous  
fermentations of milk4 ,there are a     
number of other abnormal fermentations  
in milk that occur so rarely as to be of
 but little economic importance4 ,some1 
as the colored milks1 are however1 quite
 striking1 and on this account have had 
much attention directed to them in the  

past4 ,there are bacteria that are able 
to produce various colored substances1  
such as red1 yellow1 and blue4 ,in case 
milk becomes seeded with large numbers  
of any of these kinds1 it is very likely
 to be colored by the growth4 ,red milk 
may be due to bacteria1 but more        
frequently is caused by the actual      
presence of blood in the milk1 due to a 
wound in the udder1 or the effect of a  
severe case of inflammation of this     
gland4 ,such a condition may be readily 
distinguished by allowing the milk to   
stand for a short time1 in which case1  
if due to blood1 the red corpuscles will
 soon settle to the bottom of the       
container1 while bacterial troubles     
producing a red coloration are more     
evident on the surface4  ,it is also    
claimed that certain bacteria may impart
 a soapy taste or turnip flavor to milk4
  ,cycle of fermentations in milk4 ,if a
 sample of milk is allowed to stand1 it 
will undergo a certain sequence of      
fermentations that well illustrates the 

principle that one type of organisms is 
dependent on some other type to furnish 
suitable conditions for its development4
 ,this cycle of changes that normally   
occurs in milk is as follows3 7#a7 ,the 
bacteria that come from the interior of 
the udder are the first to develop1 but 
usually the change they produce is not  
evident4  7#b7 ,of the types that gain  
admission1 subsequent to the milking1   
the acid-producing species are able to  
adjust themselves most perfectly to the 
conditions that obtain in milk4 ,within 
a few hours they greatly predominate and
 soon the milk curdles under the        
production of acid4 ,their growth1      
however1 is soon stopped by the         
accumulation of their own by-products4  
7#c7 ,the semi-solid curdled milk1 on   
account of its acid reaction then       
becomes a favorable medium for the      
growth of molds2 a prevalent form1 known
 as ,oidium lactis usually develops as a
 white velvety layer4 ,the molds in     
their growth form alkaline by-products1 

which tend to neutralize the acid       
reaction1 so that in the course of two  
to three weeks1 if the layer of the milk
 is not too deep 7an inch or less71 the 
chemical reaction of the milk becomes   
neutral or alkaline4  7#d7 ,the         
putrefactive bacteria which found their 
way into milk when it was first drawn1  
and which have remained dormant in the  
sour milk1 now find favorable conditions
 for growth4 ,as a result of their      
activity1 the milk soon undergoes a     
putrid decomposition1 which is marked by
 offensive odors4  ,if the milk is      
placed under such conditions as will    
exclude the growth of the mold1 such as 
where the air is excluded from the      
surface1 the sour milk will remain in   
that condition for an indefinite period1
 since the putrefactive bacteria are    
inhibited in their development by the   
acid1 in a manner comparable to the     
preservation of pickles in vinegar1 or  
the keeping of silage because of the    
acid that is produced as a result of the

 changes that the plant tissue undergoes
 when excluded from the air4 ,the       
preservative effect of acids is of much 
importance in the case of certain dairy 
products 7see ,chapter ,,viii74         
,fermented drinks from milk4 ,within the
 last few years a great deal of         
attention has been directed toward the  
preparation of various kinds of drinks  
from milk4 ,the use of such beverages   
has rapidly increased4 ,butter milk is  
one which meets with the greatest       
approval4 ,the true butter milk from    
cream that has been soured by the       
desirable acid-forming bacteria has a   
mild agreeable acid taste1 wholly free  
from any sharpness that is often noted  
in butter milk made from cream in which 
considerable numbers of the undesirable 
acid-forming bacteria have grown4       
,butter milk made from pasteurized cream
 soured with pure cultures will have    
good keeping qualities and is a most    
healthful drink for all classes of      
people1 even for young children4        

,butter milk is also prepared by        
allowing milk to sour and then breaking 
up the curd by stirring4 ,if the type of
 fermentation is controlled as may be   
done 7see ,chapter ,,vii71 such a form  
of fermented milk is a most desirable   
drink4 ,it is probably as healthful and 
has all the therapeutic properties that 
are ascribed to other forms of fermented
 milks such as the ,bulgarian ,yoghurt4 
,this type of fermented milk is produced
 by an acid-forming organism that can   
form large amounts of acid1 #b4j or #c4j
 per cent4 ,the casein is dissolved to  
some extent and the remainder so        
changed1 that it will remain in         
suspension for a long time in a finely  
divided form1 after the curd has been   
broken up4 ,such milk is sold under     
various names at home and abroad4 ,one  
of the authors 7,h7 has found such      
organisms in practically all milks      
examined4 ,if raw milk is kept warm 7#ih
 to #ajj ,f47 in a stoppered bottle     
which is filled full1 the acidity will  

be found to increase slowly from day to 
day1 reaching a maximum in ten to       
fourteen days4 ,if the milk is then     
examined1 it will be found to contain   
large numbers of an acid-forming        
organism very different in appearance   
from the bacteria causing the rapid     
souring of milk at ordinary             
temperatures4 ,this organism is very    
similar if not identical with the one   
found in the ,bulgarian milk to which   
the name ,b4 ,bulgaricus has been given4
 ,the use of the milk fermented by this 
organism has spread rapidly because it  
is claimed by certain ,european         
bacteriologists that it has a favorable 
effect on the health of people1         
especially those suffering from         
intestinal troubles4 ,it is not at all  
certain that ordinary sour milk or      
butter milk will not have the same      
effect2 in fact in many of the fermented
 milks sold in ,europe1 ,b4 ,bulgaricus 
has not been found1 but only the        
ordinary lactic acid bacteria4  ,several

 alcoholic drinks made from milk1 such  
as kefir and koumiss1 have been         
originated among the nomadic tribes of  
,western ,asia4 ,kefir is prepared from 
cow's milk by adding the kefir ferment  
in the form of grains which contain a   
number of kinds of bacteria and a yeast4
 ,the acid-forming bacteria impart a    
sour taste to the fermented milk1 while 
the yeast forms carbon dioxide and about
 two per cent of alcohol4 ,if the milk  
is allowed to ferment in stoppered      
bottles1 the resulting product will be  
an acid effervescing drink1 which is    
claimed to be more easily digested than 
sweet milk4 ,this drink is used         
frequently in the treatment of invalids 
but it is improbable that it is more    
easily digested than ordinary soured    
milk or butter milk4 ,the grains are    
removed from the fermented milk1 and are
 then added to a quantity of fresh milk1
 or they may be dried and kept for      
future use4 ,when needed again1 they are
 soaked in water1 then added to the     

milk4  ,koumiss is made in ,russia from 
mare's milk and has much the same       
composition as kefir4 ,in ,america and  
,europe it is made from cow's milk1 by  
adding cane sugar and compressed yeast4 
,the yeast ferments the cane sugar while
 the acid-forming bacteria ferment the  
milk sugar4 ,there is thus obtained a   
drink that is similar in composition to 
the real koumiss1 in which both the acid
 and the alcohol come from the          
fermentation of the milk sugar4 ,in     
koumiss and kefir the curd is very      
finely divided and will remain in       
suspension for a long time as with      
butter milk4  ,determination of the     
cause of taints in milk4 ,it is often of
 the greatest importance to be able to  
locate the cause of abnormal odors or   
tastes in milk1 since methods for       
overcoming the trouble can be           
intelligently applied only when the     
actual cause is known4 ,an abnormal     
condition may be caused either by the   
direct absorption of odors before or    

after the milk is drawn from the animal1
 or it may be due to bacteria4 ,if the  
milk appears bad-flavored when first    
drawn1 and if such taint becomes less   
pronounced as the milk becomes older1 it
 is likely that the trouble is due to   
some characteristic of the feed4        
,certain feeds1 like green rye1 rape1   
cabbage1 and certain of the root crops1 
like turnips1 impart a strong odor to   
milk1 if the same are fed shortly before
 milking4 ,if the tainted condition     
appears only some time after the milk is
 drawn1 it may be due to the direct     
absorption of taints from the           
surroundings in which the milk is kept1 
or it may be caused by bacteria4 ,these 
causes can often be differentiated1 by  
noting whether the taint tends to       
increase in intensity with age4 ,if such
 is the case1 it is likely that the     
cause is of germ origin1 but if the     
reverse is true1 it cannot be ascribed  
with certainty to bacteria and recourse 
must be had to other methods1 such as   

the transfer of a small quantity of the 
tainted milk to a sample of perfectly   
fresh milk1 or preferably to some milk  
that has been heated to the boiling     
point and then cooled4 ,in the case of  
an odor due to direct physical          
absorption1 it will not appear in the   
inoculated sample1 since the small      
amount transferred is not sufficient to 
be noted4 ,if it is due to living       
organisms1 the inoculation of the       
smallest quantity into a fresh sample is
 likely to reproduce the same change as 
originally noted4  ,tests for the       
bacteriological condition of milk4      
,within certain limits milk can be      
indirectly examined as to its bacterial 
content without any special equipment4  
,milk when drawn from the cow has an    
apparent acidity ranging from #j4af to  
#j4ah per cent4 ,by the use of any of   
the methods of determining acidity in   
milk1 much can be told concerning the   
number of bacteria in the milk1 and     
hence concerning its keeping quality4   

,milk that has an acidity of over #j4b  
per cent is certain to contain many     
bacteria1 and consequently will keep    
poorly4 ,such milk is of low value for  
market milk1 but may not be             
objectionable for butter or cheese      
making4 ,if the acidity is below #j4b   
per cent1 but little can be told as to  
the numbers of bacteria1 since any      
increase in acid is always preceded by  
an enormous increase in the numbers of  
acid-forming bacteria4  ,a more         
important test than the acid test1 from 
the standpoint of the butter and cheese 
maker1 and even the milk dealer1 is the 
fermentation test4 ,in its simplest     
form1 it consists in placing a sample of
 the milk to be tested in a warm place  
and noting the time required to curdle  
and the type of curd formed4 ,in this   
country the fermentation test has been  
largely supplanted by the ,wisconsin    
curd test which possesses the advantage 
of detecting the presence of bacteria   
harmful in cheese making1 especially the

 gas forming bacteria4  ,the curd test  
is helpful in detecting the source of an
 abnormal condition in a milk supply    
coming from diverse sources4 ,the milk  
furnished by each patron can be tested  
separately and the trouble located1     
perhaps in an individual herd2 the      
offending herd determined1 the test may 
then be used on the milk of individual  
cows4 ,the cheese maker and the milk    
dealer should be able not only to detect
 which of the patrons furnish him poor  
milk1 but he should be able to give the 
patron definite instructions how to     
avoid the sources of such trouble4 ,this
 information can be given only when the 
source is positively known4             
,illustration3 ,fig4 #bc4--;,curd ,test4
  ,a good curd obtained from milk       
containing no harmful bacteria but many 
desirable acid-forming organisms4  ,the 
,wisconsin curd test is made as follows3
 ,samples of the milk to be tested are  
placed in sterile pint fruit jars4 ,the 
milk is warmed to #ij ,f41 ten drops of 

rennet are added to each sample1 and as 
soon as the curd is solid1 it is cut    
into small pieces with a case knife so  
as to facilitate the expulsion of the   
whey4 ,as the curd settles to the bottom
 of the vessel1 the whey is poured off  
at intervals so that a pat of firm curd 
is left4 ,as the milk curdles the       
bacteria are enmeshed and are carried   
with the curd4 ,the jars are kept at a  
temperature of #ajj to #aje ,f41 since  
this temperature is favorable to growth 
of the bacteria that are sought1 the    
gas-forming organisms4 ,at the end of   
ten to twelve hours1 the jars are       
examined2 if the curd is solid1 the     
texture firm1 not mushy or slimy on the 
surface1 if the odor is agreeable1 it   
indicates that the milk contains few or 
none of the undesirable forms of        
bacteria4 ,if the curd is full of gas   
holes1 it is apparent that undesirable  
bacteria are present and under such     
circumstances the curd will not have an 
agreeable odor4 ,if the gas-forming     

bacteria are numerous1 the curd may even
 be spongy from the abundance of gas    
holes1 and the undesirable odor more    
pronounced4 ,such curds are tough and   
rubbery4 ,in some cases a bad flavor or 
odor is apparent even though the texture
 of the curd is not open and full of    
holes4 ,the curd1 the surface of which  
is slimy indicates undesirable          
organisms4 ,a solid curd of agreeable   
odor is indicative of the presence of   
the desirable acid-forming bacteria4    
,such a milk is excellent from the      
standpoint of the butter or cheese      
maker1 but may not be so desirable from 
the standpoint of the milk dealer on    
account of its poor keeping qualities4  
,on the other hand a milk suitable from 
the standpoint of the milk dealer1 on   
account of its low germ content1 and    
hence good keeping quality1 may give a  
poor curd test4 ,it is certain to       
contain some bacteria1 especially those 
from the interior of the udder while it 
may contain none of the desirable       

acid-forming organisms without which a  
curd of good texture and flavor can not 
be obtained4 ,the bacteria in the clean 
milk will grow rapidly at the high      
temperatures at which the curds are kept
 and the changes they will produce as to
 flavor and odor may be undesirable4    
,the milk might be judged as poor when  
in reality it might be a most excellent 
sample1 and if kept at the ordinary     
storage temperatures1 it might keep for 
days4 ,the test when used for market    
milk should be interpreted with this in 
mind4  ,illustration3 ,fig4 #bd4--;,curd
 ,test4  ,the curd obtained from milk   
containing many gas-forming bacteria4   
,the irregular1 angular holes are       
mechanical1 due to the imperfect fusion 
of the pieces of curd4  ,if the results 
are to be of any value1 the test must be
 made with care to avoid all sources of 
error2 the tester must know that the    
bacteria causing the gas and bad flavors
 in the sample were originally present  
in the milk at the time the sample was  

taken1 and that they have not come from 
the containers used or from other       
sources4 ,to insure these conditions the
 jars must be thoroughly cleaned and    
then sterilized just before use by      
placing them in cold water and bringing 
them to the boiling point1 or sterilized
 by a thorough steaming4 ,the sample of 
milk of a patron must be taken so as to 
avoid contamination from the milk of the
 other patrons4 ,this can best be done  
by filling the jars as the milk is      
poured from the patron's can into the   
weigh can4 ,in cutting the curds1 the   
knife used must be dipped in hot water  
between each test to cleanse the same4  
,in short1 the test should be carried   
out with great care so that the tester  
is certain of the results obtained4     
,other tests for the bacteriological    
condition of milk will be described in  
,chapter ,,ix4  ,overcoming abnormal    
fermentations4 ,the lactic acid bacteria
 are often looked upon as normal to     
milk1 and it is certain that they are to

 be classed as harmful1 only as they    
injure the keeping qualities of milk4   
,in milk designed for butter and cheese 
their presence is necessary4 ,at times  
these desirable forms of bacteria may   
disappear1 and be replaced by less      
desirable types4 ,in one case it was    
observed that the usual lactic bacteria 
had been replaced in a cheese factory   
supply by an acid-forming organism that 
produced an intensely bitter taste in   
the milk1 thus rendering the cheese of  
no value4 ,when such harmful forms      
appear1 they must be overcome1 and the  
normal types of bacteria replaced4 ,a   
thorough cleaning of the milk utensils1 
attention to the cattle and all places  
from which such bacteria may find their 
way into the milk is often sufficient to
 cause a disappearance of the trouble4  
,if the acid-forming bacteria have      
disappeared1 the inoculation of the milk
 with cultures in ways later to be      
discussed is often of advantage4 ,at    
times more stringent measures must be   

employed in order to destroy the harmful
 bacteria1 such as the use of strong    
disinfectants4  ,disinfection and       
disinfectants4 ,if any building or room 
becomes infected with disease-producing 
bacteria1 or if organisms causing       
abnormal fermentations become           
established in a factory1 the use of a  
disinfectant that will destroy with     
great rapidity the life of bacteria is  
necessary4 ,the disinfection of all     
types of dairy apparatus and utensils   
can be accomplished by thorough         
cleansing1 and by the use of steam or   
boiling water4 ,the disinfection of     
rooms and stables cannot be so readily  
accomplished4  ,consideration must      
always be given to the resistance of the
 organism it is desired to destroy4     
,those that form spores are very        
resistant toward all chemical agents1   
while those that do not produce these   
resistant bodies are easily killed4 ,in 
the dairy and factory1 it is often      
necessary to destroy the organisms that 

develop in decomposing organic matter4  
,here1 as in all disinfection1 a        
thorough cleaning should precede the    
application of any disinfectant4 ,some  
chemicals act as deodorants1 i4e41      
destroy the offensive odor1 without     
removing the cause4 ,it is impossible   
effectually to destroy bacteria embedded
 in a mass of organic matter1 and       
through the removal of the material     
itself1 the larger part of the bacteria 
will be removed4 ,the disinfectant then 
comes in direct contact with the surface
 to be disinfected1 consequently        
destroys the bacteria not removed in the
 cleaning4  ,all places in which dairy  
work of any kind is done should be      
provided with an abundance of light and 
air4 ,the direct rays of the sun have a 
powerful disinfecting action1 and light 
makes evident accumulations of dirt that
 in a darker room would be unnoticed4   
,ventilation keeps the rooms dry and    
thus prevents the growth of mold and the
 development of a musty odor4           

,disinfectants are divided into two     
classes3 7#a7 solid materials used in   
suspension1 or in watery solutions2 7#b7
 gaseous substances4 ,the latter are    
preferable for room disinfection when   
their use is permissible1 for the gas   
penetrates to every part of the space1  
even into the cracks4 ,gaseous          
disinfectants can only be used when the 
space is tightly closed1 for the gas    
must be confined for several hours in   
the room1 in order to make the process  
effective4 ,such disinfectants can often
 be used to advantage in the treatment  
of refrigerators and cheese rooms to    
destroy mold spores4 ,in less tightly   
closed spaces1 reliance must be placed  
on the use of the solid or liquid       
disinfectants4  ,lime4 ,quick lime or   
stone lime has a considerable           
disinfecting action4 ,on exposure to the
 air1 quick lime becomes air slaked1 and
 then has no disinfecting action        
whatever4 ,water-slaked lime used in the
 form of white wash1 lime water1 or the 

powder is effective4 ,air-slaked and    
water-slaked lime are similar in        
appearance1 but a difference can be     
noted by placing a particle of each on  
the tongue2 the air-slaked tastes like  
chalk while the water-slaked material   
causes the tongue to burn4  ,white wash 
is one of the most effective agents that
 can be used in the disinfection of     
barns1 milkrooms1 etc4 ,besides being a 
fairly strong disinfectant1 it has a    
tendency to absorb odor1 it encrusts the
 walls and lightens the interior of     
rooms4 ,it can be applied with a brush  
or with a spray pump4  ,carbolic acid   
and cresol compounds4 ,these substances 
are among the cheapest and best         
disinfectants1 but their use in the     
dairy is not advisable1 on account of   
the penetrating and lasting odor4 ,they 
can be used to advantage on the farm4   
,some of the proprietary compounds1 as  
,zenoleum1 ,kresol1 etc41 are easily    
applied1 since they mix readily with    
water in all proportions1 forming a     

milky-white emulsion that can be easily 
applied4 ,they are less caustic and less
 poisonous than carbolic acid4          
,corrosive sublimate4 ,corrosive        
sublimate is the most efficient         
disinfectant under ordinary conditions4 
,it is such an intense poison that it   
must be used with caution in places to  
which stock have access1 or in the      
dairy4 ,a solution of one part of the   
salt to a thousand parts of water 7half 
ounce to #d gallons of water7 is the    
standard generally used4  ,for gutters1 
drains1 and waste pipes in factories1   
ferrous sulphate 7green vitriol71 and   
copper sulphate 7blue vitriol71 can be  
used to advantage4 ,they are to be      
classed as deodorants rather than as    
true disinfectants4 ,since they have no 
odor of their own1 they can be used in  
any amount in the dairy4  ,sulphur can  
be used to advantage in the destruction 
of mold spores in cheese rooms1 but the 
effect of the vapors of burning sulphur 
on germ life is relatively slight1      

unless there is an abundant supply of   
moisture in the air of the enclosed     
space1 in which case sulphurous acid is 
formed which has a much greater effect4 
,to have the desired effect sulphur     
should be burned at the rate of three   
pounds to each one thousand cubic feet  
of space1 and the room kept sealed for  
at least twelve hours4 ,if the sulphur  
is placed in an iron kettle which is set
 in a vessel of water1 danger from fire 
will be avoided1 and the heat generated 
by the burning sulphur will evaporate   
sufficient water to increase the effect 
of the fumes4  ,formalin4 ,another      
disinfectant that may be used as a      
liquid or as a gas is formalin1 which is
 a watery solution of the gas1          
formaldehyde4 ,it is much more powerful 
in its action than sulphur1 and has a   
great advantage over corrosive sublimate
 and other strong disinfectants in that 
it is not so poisonous to animals as it 
is to bacteria and fungi4  ,it can be   
used as a solution 7one to five per     

cent7 for the washing of woodwork1 or   
for the treatment of any object1 since  
it has no corrosive action4 ,it can also
 be employed as a gaseous disinfectant  
for the treatment of rooms4 ,it is most 
conveniently applied by suspending large
 cloths in the room and spraying them   
with the solution1 then closing the room
 for a number of hours4  ,bleaching     
powder4 ,chloride of lime1 or bleaching 
powder as it is often called1 is a good 
disinfectant1 as well as a deodorant4   
,it is used as a wash in the proportion 
of four to six ounces to a gallon of    
water4 ,it must be used with care in    
factories since the free chlorine that  
is given off has a penetrating odor4    
,,chapter ,,vi4  ,,preservation ,,of    
,,milk4   ,it has been shown in a       
previous chapter that milk becomes      
contaminated with a multitude of        
bacteria not only on the farm where it  
is produced1 but during the various     
stages prior to its use4 ,many of the   
bacteria which find their way into milk 

are readily able to develop1 and by     
their growth1 render the milk unfit1 or 
even harmful for human food4 ,with the  
most stringent precautions that can     
reasonably be taken1 it is impossible to
 avoid all contamination2 hence1 all    
grades of milk will soon spoil1 unless  
some means of preservation is employed4 
,indeed1 of all the foods classed as    
perishable1 milk is the one that most   
rapidly deteriorates4 ,produced under   
ordinary conditions1 it is unfit for    
ordinary use in a few hours if kept at  
#gj ,f4  ,there are three possible ways 
by which milk may be preserved3 7#a7    
,the removal of bacteria that have      
gained entrance to it2 7#b7 ,the        
prevention of growth of the contained   
bacteria2 7#c7 ,the destruction of the  
contained organisms4 ,in practice at    
least two and sometimes all of these    
methods are employed4 ,the prevention of
 contamination1 a subject discussed in  
,chapter ,,iii is in reality one of the 
most efficient means of preserving milk4

 ,in milk production1 as elsewhere1     
prevention is preferable to cure4 ,milk 
produced under such conditions that its 
germ content is but a few thousand per  
cubic centimeter will keep much longer  
than that handled in the ordinary       
manner4  ,it might naturally be supposed
 that any method by which dirt is       
removed from milk would improve the     
keeping quality of milk1 due to the     
reduction of bacteria1 yet while the    
straining of the milk at the time of    
milking removes dirt of various kinds1  
it does not appreciably enhance the     
keeping quality1 owing to the fact that 
the bacteria adherent to the dirt       
particles are washed off in straining1  
and pass through the pores of the       
strainer4  ,filtration of milk4 ,it is  
possible to remove all bacteria from    
water and other fluids and thus render  
them sterile by passing through filters 
of unglazed porcelain4 ,this process can
 not be used with milk for the fat      
globules are larger than the bacteria   

7see ,fig4 #f7 and any process that     
would remove the latter would also      
remove the former4 ,the term filtration 
is applied to a process used in some    
,european cities for the removal of the 
insoluble dirt that has been introduced 
into the milk4 ,suitable containers are 
filled with layers of coarse sand at the
 bottom and with finer sand at the top4 
,the milk is introduced at the bottom   
and is forced upward through the sand4  
,such a filtering process is a very     
efficient means of removing the dirt2   
but unless the filters are kept         
scrupulously clean1 the bacteria are    
likely to grow in the filtering         
material1 so that the number of         
organisms in the milk may actually be   
increased by the filtering process4 ,it 
is necessary to remove the sand daily   
and thoroughly wash and sterilize the   
same4 ,the extra care required in       
keeping these sand filters in sanitary  
condition has been the great objection  
to their employment in this country4    

,filters of other material such as      
cellulose have been employed but with no
 marked success4  ,clarifying milk4 ,a  
much more efficient and less troublesome
 means of removing the insoluble foreign
 particles from milk is to pass it      
through a cream separator1 allowing the 
cream and skim milk to mix in the same  
container4 ,the slime that collects on  
the wall of the separator bowl is made  
up of dirt1 casein1 bacteria1 and the   
cellular debris from the interior of the
 udder4 ,the bacteria are heavier than  
the milk serum1 and would1 therefore1 be
 deposited on the wall of the bowl were 
it not for other factors that in a      
measure prevent this4 ,the movement of  
the fat toward the center of the bowl   
carries into the cream a considerable   
proportion of the bacteria in the milk4 
,the slime will always contain many more
 bacteria than the milk1 but the per    
cent of bacteria thus removed is        
relatively low1 due to the small amount 
of slime obtained from the milk1 so that

 the actual effect of clarification on  
the keeping quality of milk is          
insignificant4 ,the complete removal of 
all insoluble and therefore visible dirt
 is1 however1 regarded of sufficient    
value to warrant the use4  ,machines    
designed especially for the             
clarification of milk are now widely    
used4 ,they differ from the cream       
separator in that the milk is introduced
 at the outside of the bowl and hence   
there is no separation of the fat from  
the serum4 ,it is claimed that the      
removal of the dirt1 cells from the     
interior of the udder and bacteria is as
 efficiently done as when the separator 
is used4 ,the advantages claimed for the
 machine are that it has no effect on   
the subsequent gravity creaming of the  
milk and that less power is demanded    
than for the separator4  ,from the      
standpoint of the consumer1 all         
processes by which dirt is removed from 
milk are objectionable1 since they make 
the milk appear cleaner and better than 

it really is1 the harm having been done 
when the dirt with the adherent bacteria
 found its way into the milk4 ,the      
removal of the foreign matter that has  
been introduced into the milk will have 
but little effect in reducing the number
 of bacteria1 since a large part of the 
organisms will have been washed off the 
insoluble material4 ,all of these       
processes improve the appearance of the 
milk but have little or no influence in 
increasing its keeping quality or its   
healthfulness4  ,preservation by cold4  
,the only legitimate way of preventing  
the growth of bacteria in milk is by    
holding it at temperatures at which the 
ordinary forms of bacteria cannot       
thrive4 ,bacterial growth is greatly    
checked at temperatures approximating   
#ej ,f41 or below1 although certain     
types multiply at the freezing point or 
slightly above4 ,if food products are   
actually congealed1 no germ growth      
occurs1 and they may be kept quite      
indefinitely1 but this process cannot be

 successfully applied to milk1 as the   
fat and casein are physically changed1  
so that a normal emulsion can not again 
be made when the frozen milk is melted4 
,the fat separates in visible masses as 
though the milk had been partially      
churned4 ,on account of this fact milk  
must be stored at temperatures above the
 freezing point4 ,in ,denmark efforts   
have been made to preserve milk1 that is
 to be shipped long distances1 by       
freezing a portion of the milk1 and     
placing a block of the frozen milk in   
each can after cooling the main mass of 
milk nearly to the freezing point4 ,even
 this method has not proven practical1  
and at present reliance is placed on    
thorough chilling of the milk4 ,at #cb  
,f41 the lactic bacteria cannot grow1   
but other types1 such as certain of the 
putrefactive forms grow slowly2 the milk
 may1 therefore1 have no objectionable  
odor or taste and yet be swarming with  
bacteria4 ,in cities the practice is    
followed of placing cream in            

cold-storage during the cooler periods  
of summer in preparation for an         
increased demand1 during hot weather or 
on holidays4 ,it seems probable that    
poisoning from ice cream may1 at times1 
be due to the use of such cream4        
,preservation by the use of antiseptics4
 ,many chemical substances prevent the  
growth of bacteria when added to food   
supplies2 such substances thus used are 
called preservatives4 ,in the past some 
of these have been used in milk to a    
great extent1 but at present1 on account
 of stringent pure food laws1 they are  
employed only to a slight extent4 ,there
 is a great temptation for the small    
milk dealer in the city to employ them  
to preserve the excess of milk from day 
to day1 as through the use of a few     
cents worth of some preparation1 many   
dollars worth of milk may be kept from  
spoiling until it can be sold to the    
unsuspecting consumer4  ,formalin has   
been most widely used in milk because it
 is a most efficient preservative2 it is

 cheap and cannot be detected by the    
consumer1 although it injures the       
digestibility of the casein4 ,one ounce 
will keep one thousand pounds of milk   
sweet for twenty-four to forty-eight    
hours4 ,borax1 boric acid1 and salicylic
 acid have also been used1 but these    
substances must be employed in much     
larger quantities than formalin4        
,bicarbonate of soda has sometimes been 
used although it is not a true          
preservative4 ,its effect is based upon 
the neutralization of the acid produced 
by bacterial growth4 ,the treated milk  
does not taste sour so quickly1 and the 
curdling of the milk is also delayed4   
,many proprietary compounds for milk    
preservation have been placed on the    
market in the past1 but the use of all  
of these is illegal in most states4 ,the
 federal law also prohibits their use in
 all dairy products that pass into      
interstate commerce4  ,within recent    
years a method for the preservation of  
milk was introduced by a ,danish        

engineer1 ,budde1 which consists of     
adding to milk a very small amount of   
peroxid of hydrogen which is a very     
efficient antiseptic4 ,the peroxid is   
decomposed by some substance in the     
milk2 the products of decomposition     
being water and free oxygen4 ,the       
peroxid together with the application of
 heat at a comparatively low temperature
 7#abb ,f47 is sufficient to destroy the
 larger part of the bacteria in the     
milk4 ,practical difficulties are       
encountered in the commercial           
application1 so that it is probable the 
process will never be a commercial      
success4  ,for the preservation of      
composite samples of milk for analytical
 purposes1 such as the ,babcock test1   
strong disinfectants1 as corrosive      
sublimate1 are employed4 ,this material 
is very poisonous1 and leaves the milk  
unchanged in appearance4 ,some coloring 
matter is therefore usually mixed with  
the sublimate in making the preservative
 tablets1 so as to render their use more

 conspicuous4 ,corrosive sublimate not  
only stops all bacterial growth1 but    
quickly destroys the life of the cells4 
,bichromate of potash is generally      
employed in the preservation of         
composite samples for the ,hart casein  
test4  ,destruction of bacteria in milk4
 ,actual destruction of the life of     
bacterial cells by heat is one of the   
most important ways for preserving milk4
 ,heat easily destroys the vegetating1  
growing bacteria1 while the spores1 of  
which there are always a number in milk1
 are very resistant4 ,if1 however1 the  
growing organisms are destroyed1 the    
milk will keep much longer than if it   
had not been so treated4  ,the process  
of pasteurization was first used by the 
,french bacteriologist1 ,pasteur1 for   
the treatment of the wines of his native
 district which were likely to undergo  
undesirable types of fermentations due  
to bacteria4 ,from the wine industry it 
was applied in the brewing industry1 and
 was later found to be of the greatest  

service in the dairy industry4 ,the     
process of pasteurization may be briefly
 defined1 as the heating of milk to     
temperatures1 varying from #adj ,f4 and 
upward for a longer or shorter time1 and
 subsequently cooling to a low          
temperature1 so as to prevent the       
germination of the spores that are not  
destroyed by the heating4  ,effect of   
heat on milk4 ,when milk is heated it   
undergoes more or less profound changes1
 depending on the temperature and time  
of heating4 ,some of these changes are  
of practical importance1 since they are 
more or less evident1 and objectionable 
to the consumer4  ,in raw milk the fat  
globules are largely found in larger or 
smaller aggregates1 rather than         
uniformly distributed throughout the    
serum4 ,the surface of a mass of fat    
globules is smaller in proportion to the
 volume of the mass than is the case    
with single globules1 hence globule     
clusters encounter less resistance in   
their passage through the serum1 either 

as they rise to the surface in gravity  
creaming1 or in the separator bowl4 ,if 
these clusters are broken up1 so that   
the globules are uniformly distributed1 
the milk will cream much less rapidly   
and completely4 ,in the process known as
 homogenization of milk1 the individual 
fat globules are broken into such small 
globules1 that they cannot overcome the 
viscosity of the serum1 and they remain 
distributed throughout the milk4 ,in    
such cases1 no cream rises1 and even the
 cream separator is unable to remove the
 fat from such milk4  ,in selling       
bottled milk1 it is highly desirable    
that the cream line should show         
distinctly4 ,in normal milk1 this line  
forms in a few hours1 but where milk is 
heated to a high temperature1 and       
agitated at the same time1 the clusters 
of fat globules are broken apart and the
 creaming power injured4 ,this physical 
change is dependent not only on the     
temperature1 but also on the time of    
exposure4 ,a momentary exposure at #afj 

,f41 or for #bj minutes at #ade ,f41 is 
about the maximum limit which can be    
applied to milk without material injury 
to the creaming property4               
,illustration3 ,fig4 #be4--;,fat        
,globules in ,raw ,milk4  ,in raw milk  
the fat globules are in masses of       
varying sizes4 ,these rise to the       
surface quickly in gravity creaming4    
,the body or consistency of pasteurized 
cream may be restored by allowing the   
cream to stand for several days at low  
temperatures1 or by the addition of a   
small amount of sucrate of lime4 ,this  
substance1 known to the dairy trade as  
viscogen1 is made by adding to a thick  
solution of cane sugar1 some freshly    
slaked lime4 ,the sugar solution permits
 of the dissolving of a much larger     
amount of the lime than is possible in  
water4 ,when the liquid is allowed to   
settle1 the clear solution is then      
decanted off and is used at the rate of 
about one part to #ajj to #aej parts of 
cream4 ,the fat globules are1 by its    

action1 brought into aggregates and the 
body of the cream thus restored4        
,viscogen contains nothing that is at   
all harmful1 but milk and cream to which
 it is added must be sold under some    
distinctive name as visco-cream1 since  
the laws of practically all states do   
not allow the addition of any substance 
whatever to milk or cream4              
,illustration3 ,fig4 #bf4--;,fat        
,globules in ,heated ,milk4  ,when milk 
is heated the masses of globules are    
broken up and fat globules are uniformly
 distributed throughout the milk4       
,illustration3 ,fig4 #bg4--;,creaming of
 ,milk4  ,the cylinder on the left      
contains raw milk2 that in the center1  
milk heated to #adj ,f4 for twenty      
minutes2 on the right1 milk heated to   
#afj ,f4 for twenty minutes4 ,the dark  
line indicates the depth of the cream   
after twenty-four hours4 ,the breaking  
up of the fat globule clusters delays   
greatly the rising of the cream4        
,heated milk has a taste unlike that of 

raw milk2 to one not accustomed to it   
the taste is objectionable4 ,this change
 is due to some extent to the expulsion 
of the carbon dioxide from the milk4    
,the insipid taste of boiled water is1  
in part1 due to its freedom from carbon 
dioxide4 ,the production of this cooked 
flavor is dependent upon the time and   
temperature of exposure4 ,it has been   
claimed that heated milk is less        
digestible than raw1 and a considerable 
amount of experimental work has been    
done1 both on animals and children1 in  
order to determine the relative         
digestibility of heated and raw milk4   
,the results obtained have been         
contradictory4 ,it is claimed that      
heated milk causes such diseases as     
rickets1 scurvy and marasmus in         
children4 ,it is probably true that milk
 heated to the boiling point is less    
fitted as food for the young child than 
raw milk1 but1 on the other hand1 it has
 not been proven that properly          
pasteurized milk is an unsuitable food  

for children4 ,the best evidence has    
been accumulated in recent years1 in    
many of the large cities of this country
 and of ,europe1 where pasteurized milk 
has been used with the greatest success 
in the feeding of children of all ages4 
,the heated milk does not curdle readily
 when rennet is added due to the        
precipitation of the lime salts by heat4
 ,the curdling power can be restored by 
the addition of soluble lime salts or of
 acids4  ,purpose of pasteurization4    
,there are two reasons for the          
pasteurization of milk3 7#a7 ,to improve
 the keeping quality2 7#b7 ,to destroy  
any pathogenic bacteria it may contain4 
,the first may be called the economic   
reason2 the second1 the hygienic reason 
fur pasteurization4 ,in the selection of
 a proper pasteurizing temperature1 two 
factors must be taken into account3     
,first1 the effect of heat on milk1 and 
second1 the temperature necessary to    
destroy those forms of bacteria that are
 of the greatest importance1 as far as  

the keeping properties are concerned1   
and the pathogenic bacteria that might  
possibly be present in the milk4 ,the   
lactic acid bacteria are                
non-spore-bearing and are not resistant 
to heat4 ,most of them are destroyed    
when the milk is heated to #adj ,f4 for 
fifteen minutes or to #afj ,f4 for a    
moment4 ,to insure proper keeping       
quality1 somewhat higher temperatures   
must be employed1 such as #ade to #aej  
,f4 for fifteen to twenty minutes4      
,milk pasteurized at these temperatures 
will1 as a rule1 undergo an acid        
fermentation in much the same manner as 
will raw milk4 ,the rate with which the 
acid develops is of course much slower  
than in the raw milk1 due to the        
destruction of #ie to #ii per cent of   
the acid-forming bacteria4 ,if the milk 
has been pasteurized at higher          
temperatures1 the acid fermentation may 
not appear4 ,the spores of the          
spore-bearing organisms will be left2   
these may germinate and cause their     

characteristic change in milk1 which1 as
 previously noted1 is usually a         
sweet-curdling or a digesting           
fermentation4 ,since the changes they   
produce in the milk are not evident at  
first1 it might be used as food even    
though it was so far advanced in        
decomposition as to be undesirable or   
even harmful as food4 ,indeed one of the
 objections urged against pasteurization
 is that it destroys the natural safe   
guard1 the acid-forming bacteria4 ,many 
people are so accustomed to use this as 
the indication of spoiled milk that they
 will use milk long after it should be  
used if it does not show an acid        
fermentation4  ,the butyric acid        
organisms are spore forming and may at  
times produce their characteristic      
fermentation in pasteurized milk4 ,the  
milk shows gas formation and develops an
 objectionable odor4  ,the pathogenic   
bacteria most likely to be present in   
the milk are the typhoid and the        
tubercle organisms4 ,the typhoid        

bacillus is no more resistant to heat   
than the ordinary acid-forming bacteria1
 and all milk that has been heated1 so  
as to impart to it satisfactory keeping 
properties1 will certainly be free from 
typhoid bacilli4 ,it has sometimes been 
asserted that the tubercle bacillus is  
very resistant to heat2 some claiming   
that it is necessary to heat milk to    
#bjj ,f4 in order to destroy it4 ,other 
experimenters have asserted that lower  
temperatures would suffice1 but the     
temperatures were still above those at  
which the milk is physically and        
chemically changed by the heating       
process4 ,more recent work has shown    
that not all sources of error were      
avoided in the earlier attempts to      
determine the thermal death point of the
 tubercle bacillus1 as1 for example1 it 
has been shown by the authors that the  
scalded film that forms on the surface  
of milk when heated in an open vessel   
will protect the bacteria imbedded in   
it4 ,it has also been shown by the      

authors that a temperature of #adj ,f41 
for twenty minutes or #afj ,f4 for one  
minute will destroy the tubercle bacilli
 in milk1 in case the heating is done   
with sufficient thoroughness to insure  
all particles of the milk being heated  
to the same temperature for these       
periods of time4  ,the pasteurization of
 milk can be done in such a manner as to
 impart to it good keeping qualities and
 to insure its freedom from pathogenic  
bacteria1 and yet not impair its        
physical and chemical properties1 but   
much of the so-called pasteurized milk  
placed on the market is not treated in  
accordance with proper hygienic methods4
  ,illustration3 ,fig4 #bh4--,the       
,pott's ,discontinuous ,pasteurizer4    
,the milk is placed in the inner        
compartment4 ,for heating and cooling1  
hot or cold water is passed between the 
jackets4  ,methods of pasteurization4   
,in order to destroy the bacteria in    
milk1 it is necessary that the milk be  
heated for a varying time dependent upon

 the temperature employed4 ,a lower     
temperature for a considerable period   
may exert the same effect on the        
bacteria as a higher temperature for a  
shorter time4 ,in practice1 two types of
 pasteurizing machines are employed1    
depending on the temperature at which   
the milk is to be treated4 ,the         
discontinuous machines or intermittently
 operated pasteurizers are those in     
which the milk is heated for any desired
 time at any temperature4 ,such machines
 consist of jacketed containers the     
inner receptacle being filled with milk1
 while the outer space between the walls
 is filled with circulating hot water or
 steam4 ,the milk is kept agitated by   
the rotation of the machine4 ,after it  
is heated1 it is cooled in the same     
container by replacing the hot water    
first with cold water1 then ice water4  
,the disadvantage of this process is    
that the capacity of the machine is     
limited which precludes its use in      
places where large quantities of milk or

 cream are handled2 for the             
pasteurization of limited quantities1 it
 is very successful1 as every particle  
of milk or cream is under the direct    
control of the operator and may be      
thoroughly and efficiently treated4  ,as
 pasteurization was introduced for the  
treatment of market milk1 and for the   
preparation of cream for butter1        
machines have been devised which permit 
large quantities1 as thousands of       
pounds1 to be handled per hour4 ,it is  
evident under these conditions that the 
milk must be heated for only a short    
time1 and hence a higher temperature    
must be employed4 ,these machines are   
called continuous flow pasteurizers     
since the milk passes through them in a 
constant stream4 ,the period of exposure
 is very short1 in some only a few      
seconds2 hence1 they are sometimes      
called flash pasteurizers4              
,illustration3 ,fig4 #bi4--;,a          
,continuous ,pasteurizer4  ,the milk is 
exposed but a short time since it flows 

through the heater in a constant stream4
  ,all machines of this type possess the
 obvious disadvantage that it is        
impossible to heat all of the milk for a
 uniform period4 ,the milk in contact   
with the walls of the machine flows much
 more slowly than in the middle of the  
stream1 just as the current near the    
bank is less rapid than in mid-stream4  
,in none of the machines yet devised    
have the designers been able to overcome
 this disadvantage4 ,in a test of one of
 the most widely used pasteurizers of   
this type1 it was found that some of the
 milk passed through the machine in #ae 
seconds1 while the larger part of it was
 held for about #cj seconds1 and some as
 long as forty-five to sixty seconds4   
,if the temperature employed had been   
such as to destroy the bacteria in that 
part of the milk heated for the minimum 
time1 hygienic safety would be assured1 
but in order to avoid injuring the      
physical properties of the milk1 the    
tendency is to use as low a temperature 

as possible1 so that the milk heated for
 the minimum time may often contain     
organisms that have passed through the  
machine uninjured4  ,many devices have  
been proposed for the heating and       
cooling of the milk4 ,in many of the    
pasteurizers1 the milk flows in a thin  
stream over a metal surface1 on the     
opposite side of which is the heating   
agent1 usually steam2 while in others1  
the milk is allowed to flow through a   
vat in which revolve a series of discs  
into which steam is passed4 ,the discs  
are of considerable size2 thus1 making a
 large heating surface2 the milk is thus
 heated quickly1 and is constantly      
stirred by the rotation of the heating  
discs4 ,in other types the milk passes  
into the bottom of a chamber in which a 
dasher revolves at a rapid rate4 ,this  
catches the milk1 throwing it in a thin 
film onto the wall of the chamber1 which
 is heated with steam on the opposite   
side4 ,from such machines1 of which the 
,fjord1 the ,jensen1 and the ,reid      

machines are types1 the milk may be     
forced to a considerable height4 ,these 
are widely used in this country for the 
pasteurization of milk and cream for    
butter making4  ,milk that has been     
heated must be cooled at once by the use
 of cold water and ice4 ,in order to    
economize in the use of both steam and  
cooling agents1 the so-called           
regenerative machines were devised4 ,the
 essential feature of these machines    
lies in the fact that the cold milk     
inlet and the hot milk outlet are on    
opposite sides of a single partition2   
thus the inflowing cold milk is         
partially heated by means of the already
 treated hot milk which it is desired to
 cool4  ,in order to avoid the          
disadvantages of the continuous         
machines1 viz41 lack of control1 an     
apparatus has recently been devised     
which can handle large quantities of    
milk1 heating the same to any           
temperature for any desired time4 ,in   
such a machine the milk is first heated 

in a continuous heater1 and is then     
passed into large tanks in which it is  
allowed to remain for the desired time1 
and from which it flows over the        
coolers4 ,such an apparatus is called a 
holding machine1 and is probably the    
most feasible type of pasteurizer now on
 the market1 when all factors are       
considered4 ,in some of the continuous  
machines1 an attempt is made to         
accomplish the same result1 by building 
the machine so that the milk requires   
fifteen to twenty minutes for passage   
through the machine1 but in all such    
cases the same disadvantage of variation
 in rate of flow1 as in other continuous
 flow type of machines obtains4  ,tests 
of pasteurizing machines4 ,it is        
possible for the operator to test the   
rate of flow in a machine1 so as to     
determine whether all of the milk is    
heated for a uniform time4 ,this is done
 most easily in the following manner3   
,the machine is first filled with water1
 heating the same to the desired        

temperature1 and regulating the rate of 
flow as it would be if milk was used4   
,the flow of water is then turned off1  
and a stream of milk containing a known 
per cent of fat admitted to the machine4
 ,the time elapsing between the         
admission of milk to the machine1 and   
that at which the first sign of         
turbidity is noted at the outlet1 will  
be the minimum period necessary for any 
portion of the milk to flow through the 
machine4 ,at frequent intervals         
thereafter1 samples of the outflowing   
liquid may be collected1 noting the time
 at which each sample is taken4 ,the    
percentage of fat in the various samples
 is determined by the ,babcock test2 at 
the moment when all of the water has    
been removed1 the sample taken will show
 the same fat content as the milk used4 
,the samples taken previous to this will
 show a lower fat test1 dependent upon  
the relative amount of water and milk4  
,in this manner1 the minimum1 the       
maximum1 and the average period of      

exposure of milk in the machine tested1 
can be determined with exactness4  ,the 
accompanying table gives results that   
were obtained in the testing of one of  
the continuous types of machines4 ,the  
machine in question required about three
 hundred pounds of milk to fill it and  
was supposed to handle #a1jjj pounds per
 hour4 ,thus theoretically it should    
require twenty minutes for any portion  
of the milk to pass through the machine4
 ,as will be seen from the data1 some of
 the milk passed through within seven   
minutes after the water was shut off and
 the milk turned on4 ,the figures also  
show that not all of the water had been 
replaced by the milk in even #de        
minutes4 ,in actual practice like       
results will be obtained1 and a portion 
of the milk will be heated to the       
temperature employed but a short time4  
,in this1 the vegetating bacteria will  
not be wholly destroyed4        ,trial  
,per cent of fat in milk coming from    
machine at following times              

,per                                    
cent------------------------------------
---             of fat                  
,,minutes            in                 
milk------------------------------------
---                     #g  #aa  #ae    
#ai  #bc  #bg  #cf  #dg                 
----------------------------------------
--------   ,no4 ,i      #d4j   #j4b #j4h
 #a4f #b4j #b4d #b4f       ,no4 ,,ii    
#c4h   #j4b #j4f #a4e #a4h #b4b #b4f    
#c4j #c4d   ,no4 ,,iii    #c4e   #j4g   
#a4i #b4d #b4h #b4h #c4j #c4d #c4d      
,pasteurization of small quantities of  
milk4 ,it is often desirable to treat a 
small quantity of milk for home use1 in 
which case the commercial types of      
pasteurizers are out of the question4   
,this treatment can be done in a number 
of ways1 consideration always being paid
 to the manner of heating which should  
be done under such conditions1 as have  
been shown to be necessary for efficient
 pasteurization4 ,milk may be heated in 
tall1 narrow cans which are placed in   

hot water4 ,in the household1 milk may  
be treated by placing the filled bottle 
in a pail having a false bottom so the  
bottle shall not be broken when the pail
 is placed on the stove4 ,the pail      
should be filled with water so that its 
level is about the same as that of the  
milk4 ,the water is then heated to the  
desired temperature1 maintained for the 
requisite period of time1 and is then   
cooled as rapidly as possible4 ,during  
the heating1 the mouth of the bottle    
should be covered1 either with an       
inverted glass tumbler1 or the paper cap
 may be left in place1 simply punching a
 small hole through it so as to permit  
of the insertion of a thermometer4      
,illustration3 ,fig4 #cj4--;,a          
,pasteurizer for ,use in the ,home4  ,a 
milk bottle with a tumbler for a cover4 
,the cover prevents the formation of the
 scalded layer on the milk during the   
heating and also protects the mouth of  
the bottle from dust4  ,efficiency of   
pasteurizing4 ,it is easy to destroy    

over #ii per cent of the bacteria       
present by the use of any of the modern 
types of machines4 ,the number remaining
 after treatment will be largely        
dependent1 other things being equal1    
upon the number of bacteria before      
pasteurization4 ,the pasteurizing       
process is not one by which poor milk   
can be changed into good milk1 nor is it
 legitimate to use the process in place 
of cleanliness1 as is sometimes done4   
,there is a legitimate field for the    
process in the handling of market milk1 
as well as in the creamery2 but it      
should be used to improve the keeping   
quality1 and to insure the freedom of   
the milk from pathogenic bacteria1 when 
other protective measures have been     
carried as far as possible under the    
prevailing conditions4  ,details of     
process4 ,if the process is to be       
successful1 due attention must be given 
to certain details4 ,in the treatment of
 market milk1 care should be taken to   
use only that in which the acidity has  

not materially increased4 ,a fair       
standard is about #j4b per cent4 ,high  
acid milk usually means old milk or     
dirty milk1 either of which is very     
likely to contain many more             
spore-bearing bacteria than clean1 fresh
 milk4 ,the greater the number of       
spores1 the more rapidly will the       
pasteurized milk spoil4 ,if it is       
possible to exercise any selection of   
milk prior to pasteurization1 the rapid 
test for determination of acidity will  
prove of great advantage4  ,care should 
be taken to prevent fluctuations in the 
temperature to which the milk is heated4
 ,with varying steam pressure and       
variations in the rate of flow of milk1 
these fluctuations may be very          
considerable4 ,regulators are now made  
that will control the temperature within
 narrow limits4  ,in all pasteurized    
milk as it flows from the machine1 there
 will remain some living bacteria4 ,the 
spores will not be destroyed by any     
pasteurizing process1 and under         

commercial conditions1 vegetating       
bacteria are also present4 ,if the milk 
is not quickly chilled after heating1   
these forms will grow1 and their        
development is particularly hastened by 
the destruction of the lactic bacteria1 
the acid of which would otherwise hold  
them in check4 ,the result is that1     
unless immediately chilled1 pasteurized 
milk spoils almost as rapidly as though 
it had not been heated at all4          
,efficient and rapid cooling are1       
therefore1 as essential a portion of the
 process as the heating itself4  ,care  
should also be taken to protect the milk
 from contamination after treatment4    
,every utensil with which it comes in   
contact should be sterilized4 ,the      
bottles should be thoroughly washed and 
sterilized and subsequently protected   
from dust until used4  ,sterilization of
 milk4 ,it is possible to render milk   
sterile by the use of temperatures above
 the boiling point of water1 where it is
 heated in a closed vessel1 in which    

steam under pressure is generated4 ,such
 milk is often found in the ,european   
markets4 ,in our own country1 the only  
milk of this kind is the so-called      
evaporated milk4 ,in this process sweet 
fresh milk is evaporated in vacuum pans 
to about one-third of the original      
volume4 ,this is then placed in tin     
cans1 which are treated1 as in the      
canning of such vegetables as peas and  
corn1 by heating the milk to #bcj or    
#bdj ,f4 for a few minutes4 ,in this    
process1 the bacteria 7spores as well as
 vegetating forms7 are completely       
killed1 and the milk acquires a brownish
 tint1 due to the caramelization of the 
sugar4 ,the appearance of the product is
 very similar to cream1 and previous to 
the passage of the pure food law1 it was
 sold as evaporated cream4  ,condensed  
milk is not wholly free from bacteria1  
but is sufficiently thick1 by reason of 
its treatment so that the contained     
bacteria cannot grow4 ,they remain      
dormant in the milk1 but as soon as it  

is diluted to a normal consistency1     
growth takes place1 and the milk rapidly
 spoils4 ,condensed milk is prepared by 
adding cane sugar to fresh sweet milk1  
then evaporating the mixture to         
one-third the original volume1 forming a
 semi-solid product4 ,syrups owe their  
keeping qualities to the same factor1 as
 condensed milk1 i4e41 the high         
consistency4  ,milk is also preserved by
 wholly evaporating the water1 thus     
leaving a dry powder1 which on being    
mixed with water again will have much   
the same properties as the original     
milk4 ,various methods have been devised
 for the preparation of these milk      
powders1 all of which have been patented
 by the inventors4 ,if the powder is to 
be kept for long periods1 skim milk must
 be used1 since the fat slowly undergoes
 changes which cause it to have a rancid
 odor4 ,these dry preparations are      
largely used by bakers in place of fresh
 milk4     ,,chapter ,,vii4  ,,bacteria 
,,and ,,butter ,,making4   ,in the      

making of butter it is necessary to     
concentrate the milk fat into a small   
volume4 ,this process1 known as         
creaming1 may be accomplished by        
gravity1 if the milk is allowed to stand
 undisturbed1 the fat globules rising   
slowly to the surface4 ,much more rapid 
separation may be secured1 by placing   
the milk in a rapidly revolving         
container in which it is subjected to   
centrifugal force1 which causes the     
heavier parts of the milk to pass to the
 outside of the bowl1 while the lighter 
part1 the fat1 collects at the center of
 the revolving bowl4 ,there is an       
enormous number of fat globules in milk1
 over #e1jjj1jjj1jjj in each cubic      
centimeter1 and as these move through   
the milk serum1 they carry with them    
many of the bacteria4 ,the cream is thus
 much richer in bacteria than is the    
skim milk1 or even the milk before      
separation4 ,besides the mechanical     
separation in the manner described1 the 
method of creaming is of importance1 in 

determining not only the number but also
 the kind of bacteria in the cream4     
,methods of creaming4 ,in the           
shallow-pan method of creaming1 the milk
 is kept at ordinary room temperatures4 
,these temperatures favor especially the
 growth of the acid-forming bacteria4   
,the milk is usually sour by the time   
the cream is removed from it2           
consequently1 the bacterial content of  
the cream is high4 ,moreover1 the cream 
is exposed to air contamination1 and is 
thus seeded with molds1 and those forms 
of bacteria that are always found in the
 air4 ,the cream obtained in this manner
 is likely to contain not only numerous 
bacteria1 but a great variety of forms1 
some of which undoubtedly are the cause 
of the poor keeping qualities of butter 
made from such cream4  ,in the more     
modern method of gravity creaming1 in   
which the milk is placed in deep narrow 
cans kept in cold water1 the conditions 
are not favorable for the growth of     
acid-forming bacteria4 ,if the milk is  

produced under clean conditions1 and is 
placed in cold water at once1 the       
bacterial content of the cream will be  
low1 and it will be less likely to      
contain undesirable forms than the cream
 which is obtained from the shallow     
pans4  ,in separator cream the bacteria 
will be represented by the kinds present
 in the milk at time of separation4 ,if 
this milk is quite old1 the cream will  
contain large numbers of bacteria2 if1  
however1 early separation is made and   
the milk is clean1 the bacterial content
 of the cream will be low4  ,types of   
butter4 ,butter may be divided into two 
types--acid or sour-cream1 and          
sweet-cream1 depending upon whether the 
cream is allowed to undergo the acid    
fermentation or not before it is        
churned4 ,in southern ,europe1 it is the
 custom to churn the cream as sweet as  
possible1 and the resulting product     
possesses only the natural1 or primary  
milk flavor4 ,to one accustomed to      
butter made from sour or ripened cream1 

this taste is flat1 and if the butter is
 free from salt1 may remind one of      
grease4 ,sweet-cream butter has a       
delicate flavor when it is made from    
good milk1 and the taste for it is      
rapidly acquired4 ,in some centers1 as  
in ,paris1 the market demands this type 
of butter quite exclusively4  ,if the   
cream is allowed to undergo the acid    
fermentation before churning1 the butter
 has a much higher degree of flavor and 
one that differs materially in kind4    
,under primitive methods1 it was        
difficult to keep the cream sweet until 
it could be churned4 ,on the small farm 
with gravity creaming in shallow vessels
 and infrequent churning1 the cream was 
certain to be sour when churned4        
,undoubtedly1 the making of butter from 
sour cream came into use because of its 
greater convenience2 people became      
accustomed to sour-cream butter1 and at 
the present time it is used in the      
greater part of the world1 and is the   
type made in all of the great dairy     

countries4  ,ripening of cream4 ,in     
modern dairy practice the souring of the
 cream is called the ripening process1  
and is1 where the best methods are      
employed1 largely under the control of  
the butter maker4 ,the changes that go  
on in the ripening process are the same 
as have been discussed in the acid      
fermentation of milk4 ,the increase in  
acid is accompanied by an enormous      
increase in the number of bacteria2 the 
ripe cream will contain hundreds of     
millions of bacteria in each cubic      
centimeter4 ,the effect of this germ    
life is to improve or injure the butter1
 depending upon the class of bacteria to
 which it belongs4 ,the problem of the  
modern butter maker is to control the   
kinds of bacteria growing in the cream4 
,the temperature at which cream is held 
during the ripening process is favorable
 to the growth of the acid-forming      
bacteria2 hence1 in ripe cream1 they are
 practically the only kind of bacteria  
to be found4 ,it must be remembered     

however1 that there are different       
classes of acid-forming organisms1 some 
of which produce desirable flavors1     
while others are distinctly harmful4    
,the intensity of flavor of butter is1  
in a general way1 directly related to   
the amount of acid that is formed in the
 cream4 ,a low acidity at time of       
churning is usually associated with a   
mild flavor1 while a higher degree of   
acidity1 up to a certain point1 imparts 
a more pronounced flavor to the product4
 ,if cream is over-ripened1 the quality 
of the flavor is seriously impaired4    
,in determining the acidity of cream1 a 
definite volume is taken1 and the       
acidity determined by titration1        
expressing the results as such a per    
cent of lactic acid4 ,manifestly1 the   
amount of fat in the cream influences   
the apparent per cent of acidity4 ,the  
acidity will not usually exceed #j4e to 
#j4g per cent1 but in reality the serum 
will contain more than this1 as the acid
 is formed in the serum1 the butter fat 

having no role whatever4 ,in a very rich
 cream1 #dj to #ej per cent fat1 it is  
impossible to develop more than #j4d to 
#j4e per cent of acidity1 and the flavor
 of the butter will be low1 because of  
the relation between the amount of acid 
and fat1 while in a thin cream having   
the same acidity1 the ratio between the 
amounts of fat and acid will be very    
different4 ,for example1 in one hundred 
pounds of #ej per cent cream of #j4e per
 cent acidity there will be one-half    
pound of acid and fifty pounds of fat2  
in the same quantity of cream containing
 #bj per cent of fat and having an      
acidity of #j4e per cent there will be  
one-half pound of acid to twenty pounds 
of fat4 ,the flavor of the butter from  
the rich cream will be quite different  
in intensity from that made from the    
thinner cream4  ,the acidity of cream   
cannot be determined with any degree of 
accuracy by the taste or odor4 ,every   
butter maker should have some method of 
determining the degree of acidity in his

 cream1 so that he may better control   
the flavor of his product4 ,several     
methods have been devised for this      
purpose and the necessary apparatus is  
sold by all dairy supply houses4  ,the  
effect of the ripening of the cream is  
shown not only in the flavor of the     
product1 but in a number of other ways4 
,sour cream churns more easily1 and more
 exhaustively than does sweet cream4 ,it
 is supposed that the fat globules are  
surrounded by a film of albuminous      
material which prevents their coalescing
 readily4 ,during the ripening process1 
the action of the acid apparently       
dissolves this enveloping substance1 and
 the globules cohere more easily in the 
churning process4  ,when raw cream is   
used the ripened-cream butter keeps     
better than that made from sweet cream4 
,in sweet cream there are few lactic    
bacteria1 the majority of the bacteria  
present being of various kinds1 many of 
which may be injurious1 so far as the   
keeping quality is concerned4 ,in       

sour-cream butter the lactic bacteria   
make up over #ii per cent of the        
bacteria present1 and their presence    
tends to prevent the development of     
undesirable non-acid forms4  ,source of 
butter flavor4 ,the flavor of           
ripened-cream butter has been shown to  
be directly connected with the          
acid-fermentation of the cream4 ,the    
amount of lactic acid formed from the   
sugar fermented is dependent upon the   
kind of bacteria present4 ,the          
acid-producing organisms that are       
desirable from the standpoint of the    
butter maker form comparatively small   
amounts of other by-products1 but these 
undoubtedly affect the flavor of the    
butter4 ,as fats have the power of      
absorbing odors1 the butter fat absorbs 
some of the by-products of the acid     
fermentation1 thus acquiring a certain  
aroma and flavor4  ,it is not necessary 
that the cream be ripened1 in order to  
have the fat acquire a flavor1 for if   
sweet cream is churned with a           

considerable proportion of sour milk1   
the butter will have much the same      
flavor1 both as to intensity and kind1  
as though the cream had been allowed to 
sour naturally4 ,a process of butter    
making known as the ,le,clair method is 
based on this principle4 ,the           
flavor-producing substances can also be 
absorbed by the butter after it is      
churned1 by working the butter in       
contact with sour milk4 ,attempts have  
been made to add pure lactic acid to the
 cream1 instead of allowing the acid to 
be formed by the bacteria1 but while the
 physical effect on the cream is the    
same1 the flavor and aroma of the butter
 are deficient1 because the acid itself 
does not supply the necessary aromatic  
products4 ,this emphasizes the          
importance of the by-products of the    
acid fermentation other than the        
lactic-acid4  ,in the past numerous     
attempts have been made to find         
organisms that might be added to the    
cream1 in order to produce the delicate 

flavor characteristic of the best type  
of butter4 ,some bacteriologists have   
claimed that the source of the          
flavor-giving substance was to be found 
in the decomposition products of the    
nitrogenous constituents of the milk4   
,none of these attempts have stood the  
test of practical use in creameries1 and
 it has been demonstrated that the      
finest type of butter can be made by the
 use of lactic bacteria alone4          
,formerly1 when butter was made wholly  
from cream soured under natural         
conditions1 a much higher degree of     
flavor was developed4 ,under present    
market demands1 a less pronounced flavor
 is desired1 a condition more readily   
met by the use of modern methods4       
,importance of butter flavor4 ,the      
importance of flavor in determining the 
commercial value of butter is evidenced 
by the relatively high value placed upon
 this factor in scoring1 viz41 flavor1  
#de points2 body or texture1 #be points2
 color #ae2 salt #aj2 and package #e    

points4 ,the factors on which butter is 
judged1 are with the exception of       
flavor1 wholly under the control of the 
maker1 but as the production of flavor  
is dependent on the kind of bacteria    
present in the cream1 it is a far more  
difficult matter to control1 and yet it 
is of the utmost importance in          
determining the value of the product4   
,the flavor of the butter is dependent  
on the quality of the cream4 ,if this is
 dirty and sour1 the maker has little   
control over the type of fermentation1  
and hence1 little control of the flavor 
of the butter4 ,this has led in some    
cases to the grading of the cream1      
basing the division on the acidity1     
flavor1 and fat content4 ,such practice 
is entirely justifiable1 as a better    
quality of butter can be made from      
fresh1 sweet cream than from that       
already fermented4 ,it is noteworthy    
that the quality of butter has not      
improved since the introduction of the  
centralizer system1 in which cream is   

shipped for long distances4  ,control of
 the type of fermentation4 ,in the older
 methods of butter making1 there was    
little or no control of the type of     
fermentation that took place in the     
cream4 ,where milk is produced under    
clean conditions1 and kept at ordinary  
temperatures1 it will generally undergo 
fermentation changes1 due to the        
desirable type of acid-forming          
organisms4 ,in milk1 which is less      
carefully handled1 the undesirable      
bacteria are more abundant and the      
quality of the butter of lower grade4   
,when butter was made on the farm1      
before the development of the factory   
system1 it was not a question of vital  
importance whether the product was      
uniform from day to day1 but with the   
advent of the modern creamery1 turning  
out thousands of pounds of butter per   
day1 and with the extension of the      
markets for the product1 the question of
 uniformity came to be of much          
importance4 ,a uniform product can be   

secured only by the control of the type 
of fermentation in the cream1 or by the 
control of the kinds of bacteria that   
cause the souring of the cream4 ,modern 
methods of butter making have been      
devised on the basis of an improvement  
in the ripening process4  ,starters4    
,from the earliest practice of allowing 
the cream to stand until sufficient     
quantity had accumulated for churning1  
it was only a step1 but a most important
 one1 to the addition of sour milk1 sour
 cream1 or butter milk1 to hasten the   
ripening process4 ,this was the         
beginning of the modern starter4        
,experience demonstrated that the       
addition of these already fermented     
liquids exercised a desirable effect    
upon the production of butter flavor1   
even though1 at that time1 the          
phenomenon of milk fermentation was not 
satisfactorily understood1 and the      
relation of bacterial by-products to the
 production of flavor in butter was not 
recognized4  ,as a result of experience 

alone1 improvements in the development  
of the home made starter took place4 ,by
 careful selection of clean milk1 and   
the natural fermentation of this under  
carefully controlled conditions1 as well
 as the control of the temperature of   
the cream during the ripening1          
improvement in the technique of cream   
ripening gradually developed4 ,more and 
more attention was given to the         
preparation of the starter1 and its     
propagation from day to day1 under      
conditions which would prevent its      
deterioration4 ,this method of utilizing
 naturally fermented milk or cream was  
gradually extended1 until it became     
almost universal in the larger          
butter-producing districts4  ,in #ahij a
 more refined and scientific process was
 introduced by the ,danish              
bacteriologist1 ,storch4 ,recognizing   
the fact that butter flavor was         
attributable to the development of the  
bacteria present in the ripening cream1 
he conceived the idea of isolating the  

various types of organisms found in milk
 and testing them as to their effect on 
the quality of flavor4 ,selection was   
then made of the most favorable         
flavor-producing types1 and these were  
propagated in suitable culture media1   
such as skim milk1 which was rendered   
more or less perfectly sterile by       
pasteurization or sterilization4 ,under 
such conditions the addition of a       
selected ferment could be made to the   
fresh cream1 and so control the type of 
fermentation which occurred therein4 ,an
 essential requisite in any organism    
used for this purpose must be the       
ability to produce relatively large     
amounts of acid rapidly at ordinary     
ripening temperatures1 and also to form 
sufficient quantities of the proper     
flavor-producing substances to impart a 
suitable flavor to the butter fat4 ,such
 starters are known as pure culture or  
commercial starters1 and are prepared in
 both liquid and dry form4 ,at present  
they are used to a greater or less      

extent in all of the leading dairy      
districts4  ,liquid starters consist of 
a mass of sterile nutrient medium1 milk 
or beef broth1 inoculated with the pure 
culture4 ,the dry starters are made by  
adding liquid cultures1 containing the  
growing bacteria1 to some absorbing     
material1 such as milk sugar1 milk      
powder1 or starch1 the whole mass being 
dried at low temperatures1 so as not to 
injure the bacteria4 ,under such        
conditions the bacteria1 exist in a     
dormant state1 and are protected from   
their own by-products1 to which they    
would be exposed if maintained in liquid
 cultures4 ,the keeping quality1        
therefore1 of dry cultures1 is much     
better than that of liquid cultures4    
,by the use of the pure-culture         
starters1 the butter maker is able to   
add to his cream the same kind of       
bacteria from day to day1 and the butter
 will be more uniform than when the less
 constant home-made starter is employed4
 ,in cream to which the starter is      

added1 there are present a greater or   
less number of acid-forming bacteria1   
depending upon the age of the cream1 and
 upon the condition under which it was  
produced4 ,these will grow during the   
ripening process1 and the flavor of the 
product will be the result of the       
mixture of the bacteria in the cream4   
,the maker can not1 therefore1 be       
certain that the addition of a pure     
culture to raw cream will effectively   
control the type of fermentation4 ,this 
can be secured only by first destroying 
the existing bacteria in the cream1     
before the selected culture is added4   
,heating the cream accomplishes this2   
and in cream thus freed from the various
 kinds of bacteria1 the butter maker can
 insure the dominance of the desirable  
types1 contained in the pure-culture    
starter4 ,if the cream can be obtained  
in a sweet condition1 the maker through 
this process of pasteurization1 and the 
use of pure cultures1 secures almost    
perfect control over the type of        

fermentation that occurs in the cream1  
and thus exercises control over the     
degree and kind of flavor of the        
product4 ,this most scientific type of  
butter making is now used by the most   
progressive butter makers in the leading
 butter-producing regions of the world4 
,pasteurization of the cream also       
distinctly improves the keeping quality 
of butter1 a condition doubtless due to 
the freedom of the same from organisms  
other than the lactic bacteria4 ,this is
 a factor of as much importance as      
uniformity1 because under modern        
business conditions1 the surplus        
production must be kept in storage1 and 
it is essential that the quality should 
not deteriorate materially during this  
time4  ,process of pasteurization for   
butter making4 ,in the pasteurization of
 market milk1 it is necessary to take   
into account the effect of heating on   
the physical and chemical properties of 
the milk1 and the degree of heat that   
can be employed is limited4 ,in         

pasteurizing cream for butter1 there is 
no such limitation1 and the cream may be
 heated to any temperature desired4 ,in 
,denmark where the process of           
pasteurization has been used most       
extensively1 temperatures ranging from  
#agf ,f4 to #aij ,f4 are used4 ,the     
machines are of the continuous flow     
type1 and the cream rather than the     
whole milk is treated4 ,to prevent the  
spread of tuberculosis and other        
diseases1 the ,danish government        
requires that all cream and milk be     
heated to #agf ,f41 before the skim milk
 or butter milk is returned to the      
farms4  ,the heating of the butter fat  
to high temperatures has an injurious   
effect on the texture of the butter1    
unless the cream is cooled to #ej ,f41  
for a period of at least two hours      
previous to churning4  ,propagation of  
starters4 ,as has been previously shown1
 the quality of butter depends on the   
kind of bacteria in the cream or in the 
starter added4 ,the commercial starters 

contain lactic acid bacteria that have  
been selected with especial care2 most  
of the starters now sold contain but a  
single kind of bacteria2 hence1 are     
often called pure-culture starters4 ,the
 package purchased contains but a small 
quantity1 and before the starter can be 
used in the ripening of cream1 it must  
be increased in amount4 ,it must also be
 propagated from day to day so that a   
fresh starter shall be available daily  
for addition to the cream4 ,the         
propagation of the starter must be done 
with especial reference to keeping it in
 good condition and in as high a state  
of purity as possible4  ,in the past the
 starter was propagated1 by adding the  
contents of the bottle purchased to a   
small amount of milk that had been      
heated and cooled2 this1 if kept in a   
warm place1 would be curdled in         
twenty-four hours1 and could be used for
 the inoculation of a large mass of     
milk1 that had been treated in a like   
manner1 and which1 when curdled1 was    

added to the cream2 a small amount was  
saved for the purpose of again          
inoculating a mass of milk that had been
 heated and cooled4 ,following this     
method it was very difficult to keep the
 culture from becoming contaminated with
 other forms of bacteria4 ,more recently
 the most successful butter makers have 
propagated the so-called mother starters
 in small vessels1 and have used the    
larger mass of starter for the          
inoculation of the cream alone4  ,glass 
vessels are preferable for the          
propagation of the mother starters since
 they are impervious and through the    
transparent wall the condition of the   
ripened starter can be more easily      
determined than in a metal or           
earthenware vessel4 ,an ordinary milk   
bottle with an inverted tumbler for a   
cover1 to protect the starter from      
contamination from the air1 is a most   
convenient vessel4  ,the starters may be
 propagated either in whole or skim     
milk2 the former is preferable since1 in

 most creameries1 it can be more easily 
selected4 ,the quality of the milk used 
has much to do with the quality of the  
starter2 it should be as fresh and clean
 as it is possible to obtain4 ,the clean
 bottle should be filled half to        
two-thirds full1 covered and heated in  
some manner so that the milk shall be at
 a temperature close to the boiling     
point for fifteen to twenty minutes4    
,the heating may be done by placing the 
bottles in water1 which is heated on a  
stove or by steam1 or the bottles may be
 subjected to streaming steam4 ,the milk
 is cooled quickly and the contents of  
the package purchased added and well    
mixed with the milk4 ,in the case of the
 dry starters1 the mixing should be done
 with especial care4 ,the bottle is kept
 in a warm place and in twenty-four to  
thirty-six hours1 the milk should be    
curdled4 ,a second bottle must be       
treated as before and inoculated from   
the first1 and the process repeated     
daily since the bacteria must have fresh

 food1 if they are to be maintained in  
good condition4  ,in order to accomplish
 this1 the maker must be able to        
maintain constant conditions from day to
 day1 especially with reference to the  
amount of the ripened starter that is   
transferred to the fresh bottle of milk1
 and the temperature at which the       
bottles are kept4 ,a spoon1 arranged as 
shown in ,fig4 #ca1 enables one to carry
 a definite amount of the ripened       
starter to the bottle of milk to be     
inoculated and a constant temperature   
box 7,fig4 #cb7 permits of the          
maintenance of the same temperature from
 day to day4 ,through careful           
supervision of these points1 and by     
taking care at every step to avoid the  
introduction of contaminating organisms1
 the purity of the culture can be       
maintained1 and the bacteria kept in a  
healthy condition4  ,the starter is used
 because of the acid-forming bacteria it
 contains2 it is said to be ripe and in 
the best condition for use at the time  

it contains the greatest number of      
living bacteria4 ,it has been found by  
experiment that this is at the time the 
milk curdles at ordinary temperature1 or
 when the acidity is about #j4f-j4g per 
cent4 ,if the acidity is allowed to     
increase to #j4h or #j4i per cent1 the  
number of bacteria will be less and a   
larger amount of the starter must be    
used in order to ripen a definite amount
 of cream in the desired time4 ,the use 
of an overripe starter may also have an 
injurious effect on the flavor4         
,illustration3 ,fig4 #ca4--;,bottle for 
,mother ,starters4  ,a milk bottle with 
a tumbler for a cover and a spoon for   
inoculating the other bottles enables   
the butter maker to propagate the       
starters without contamination4  ,the   
ripened starter should be perfectly     
homogeneous1 showing no bubbles of gas  
or free whey2 the odor should be        
agreeable and the acid taste mild2 on   
shaking1 the curd should break up into a
 smooth1 creamy liquid free from lumps4 

,this is especially important in the    
starter that is to be added to the      
cream1 since otherwise the starter      
cannot be uniformly mixed with it and   
white specks of curdled casein will be  
noted in the butter4  ,illustration3    
,fig4 #cb4--;,an ,incubating ,chamber   
for ,starters4  ,the inner compartment  
will hold a pail of water and the       
bottles for the mother starters4 ,the   
temperature can be kept at any desired  
point by the use of warm or cold water4 
,the four-inch space between the walls  
is filled with hay or mineral wool4     
,the firmness of the curd is not so     
dependent on the amount of acid formed  
as upon other factors4 ,if the curd     
shrinks to any extent and the whey is   
expressed1 it is certain to produce a   
starter that will contain lumps that    
cannot be broken up4 ,with a pure       
culture of lactic bacteria1 there is    
little difficulty in this regard1 but as
 soon as gas-forming bacteria are       
introduced1 trouble is likely to result4

  ,in the propagation of starters1 it is
 always to be remembered that the       
bacteria1 although invisible to the eye1
 are living things1 and unless          
conditions are favorable in every       
particular1 it is impossible to keep    
them in a healthy condition1 so that    
growth in the cream is rapid1 producing 
the acid demanded for churning1 and     
imparting to the butter the desired     
flavor1 both as to degree and kind4 ,no 
part of the daily routine of the butter 
maker should be performed with more care
 than the preparation of the starters1  
both the mother starters1 and the larger
 one for addition to the cream4 ,the    
latter can best be made in one of the   
many forms of starter cans now on the   
market1 since by their use1 the maker   
can heat and cool the milk with little  
trouble1 and can maintain the starter at
 any desired temperature4 ,better       
starters cannot be made in them than by 
the use of simple and improvised        
apparatus1 but better results can be    

obtained with the same expenditure of   
time and labor4  ,in the handling of the
 large starter1 care should be used not 
to overripen1 since the larger quantity 
is more likely to whey off than is the  
smaller starter4 ,skim milk rather than 
whole should be used for this4 ,it      
should be selected with care and heated 
to #bjj ,f4 for thirty minutes4 ,when it
 is impossible to secure fresh milk for 
starter making purposes1 either         
condensed skim milk or milk powder may  
be used4 ,the condensed milk is diluted 
with water until its volume is about the
 same as the milk before concentration2 
the mixture is then treated the same as 
fresh milk1 being heated and cooled     
before inoculation4 ,in the case of milk
 powder1 one part of the powder is added
 to ten or twelve parts of water1       
allowed to dissolve as far as possible1 
and the mixture heated and cooled4      
,either of these liquids will give      
satisfactory starters2 the cost however 
is high1 and in most places milk can be 

obtained more cheaply4 ,the inoculation 
and the temperature should be so        
controlled1 as to ripen the starter at  
the time it is to be needed4 ,these     
conditions must be determined by the    
maker for himself4 ,it should be        
remembered that the bacteria grow much  
more rapidly1 as the temperature is     
increased2 and hence1 the amount of     
inoculation is dependent on the         
temperature at which the starter is to  
be kept4  ,when the starter is          
propagated under practical conditions1  
it sooner or later deteriorates1 either 
in acid production1 or in flavor1 and a 
new pure culture must be procured from  
the manufacturer4 ,it is impossible to  
give a hard and fast rule as to the     
length of time a starter can be kept in 
good condition4 ,it will depend on how  
well the maker satisfies the conditions 
necessary for maintaining its purity and
 strength4 ,the use of imperfectly      
sterilized milk1 or dirty utensils soon 
contaminates it2 overripening is likely 

to injure the flavor4 ,one of the most  
frequent troubles encountered is the    
appearance of a slimy or ropy condition 
in the starter1 although the acidity    
developed may be normal and the flavor  
desirable4 ,it has been found that this 
condition is not necessarily due to     
contamination1 as was considered true in
 the past1 but rather to some change in 
the lactic bacteria themselves4 ,if the 
propagation is continued1 the slimy     
condition will often disappear4         
,starters in process butter and         
oleomargarine4 ,the advance which has   
recently been made in the science and   
practice of cream ripening and butter   
production is utilized most effectively 
in the treatment of cream in the        
renovating process4 ,old1 soured1 and   
stale cream is reduced in acidity by the
 addition of lime4 ,the cream is then   
pasteurized and aerated to expel the    
odors as much as possible4 ,a large     
amount of starter is then added and the 
cream immediately churned4 ,under these 

conditions1 the bad flavors are         
materially reduced in intensity1 and    
desirable flavors absorbed by the fat   
from the selected starter used4 ,it is  
thus possible to produce butter of good 
quality from cream that would at first  
be regarded as quite unsuitable for     
butter production4  ,in the manufacture 
of oleomargarine the same principle is  
utilized4 ,the butter aroma and flavor  
is imparted to the neutral oils and     
tasteless fats by mixing the same with a
 properly prepared starter4 ,renovated  
or process butter is given a desirable  
flavor in the same way4  ,wash water4   
,it has been found that the purity of   
the water used in washing the granular  
butter has a marked influence on the    
keeping quality4 ,if the water is from a
 shallow well into which surface water  
finds its way1 it is certain to contain 
large numbers of those types of bacteria
 that are found in the soil1 while if it
 comes from a deep well that is properly
 protected from surface contamination1  

the bacterial content of the water will 
be low and no injurious effect on the   
butter will be noted4 ,when it is       
impossible to obtain pure water for     
washing purposes1 a proper supply may be
 secured by sterilizing the water4 ,the 
most convenient way of heating the water
 is by the direct injection of steam4   
,it is necessary to use that coming     
directly from the boilers and not the   
exhaust from the engine1 since the      
latter is likely to contain small       
amounts of oil that will impart to the  
butter an objectionable flavor4 ,after  
cooling1 the water is ready for use4 ,it
 has been shown that the cost of        
treating an impure water is more than   
covered by the increased returns from   
the product4  ,a pure and healthful     
water supply should be one of the       
essential things of every dairy1        
creamery1 and cheese factory1 not only  
for the sake of the quality of the      
product1 but also to avoid contamination
 of products with disease-producing     

bacteria4  ,bacteria in butter4 ,the    
germ content of butter will depend on   
the type of cream4 ,sweet-cream butter  
contains but few bacteria4 ,in          
sour-cream butter the content in        
bacteria will be greatly increased1     
especially as to lactic organisms4      
,often1 it may amount to several        
millions of organisms per gram4 ,the    
germ content of butter is said to be    
greater on the outside of a package than
 within the mass1 due doubtless to the  
free access of air1 thus favoring the   
growth of the aerobic forms4  ,the      
composition of normal butter does not   
favor the growth of the majority of     
kinds of bacteria that are contained in 
it4 ,the washing process removes much of
 the material suitable as food for the  
bacteria1 such as sugar and albumen4 ,if
 considerable butter milk is left in the
 butter1 the growth of bacteria will be 
quite rapid1 at first1 but does not     
continue for any considerable length of 
time4 ,the addition of salt also tends  

to restrain the growth of most kinds of 
bacteria4  ,butter is at its best when  
it is perfectly fresh4 ,deterioration   
begins within a short time and the      
rapidity with which the changes go on is
 dependent on the temperature at which  
the butter is stored4 ,the temperature  
of the butter rooms in the large cold   
storage plants is kept below #j ,f4 ,the
 butter in such rooms will deteriorate  
very slowly1 but on removal from the    
cold rooms and in storage at ordinary   
temperatures deterioration goes on more 
rapidly than would have been the case   
when the butter was fresh4 ,at the      
temperature of an ordinary refrigerator 
the changes go on much more rapidly4    
,this fact has often been looked on as  
indicating that the factors causing the 
changes are biological ones4 ,the       
influence of temperature in accelerating
 the changes would be the same if no    
biological factor were active4  ,that   
biological factors are of importance is 
indicated by the fact that the keeping  

quality of the product is profoundly    
affected by the quality of the cream4   
,butter made from sweet1 fresh cream1   
that has been thoroughly pasteurized1   
has the best keeping quality1 while     
butter made from such cream1 but not    
pasteurized1 has the poorest keeping    
quality1 especially when no salt is     
added4 ,every process by which the      
desirable lactic bacteria are increased 
in proportion to other kinds has a      
marked effect in enhancing the keeping  
quality of the butter4 ,thus1 the use of
 pure cultures in raw cream1 and        
pasteurization together with the pure   
cultures1 have a marked beneficial      
effect4  ,the addition of preservatives 
exerts an effect on keeping quality4    
,borax is the chemical most frequently  
employed for this purpose4 ,its use is  
allowed in ,australia and ,new ,zealand 
in butter that is shipped to ,england1  
but the use of all preservatives is     
forbidden in the ,united ,states4  ,the 
size of the package also has an effect  

on the keeping quality2 the smaller the 
package1 the greater is the surface     
exposed to the air and the more rapidly 
the butter deteriorates4 ,butter used in
 the ,united ,states ,navy is packed in 
hermetically sealed cans so as to       
exclude the air as far as possible4     
,from the fact that any condition which 
restrains or inhibits the growth of     
micro-organisms has a tendency to       
improve the keeping quality of butter1  
it would appear that the detrimental    
changes in the quality of butter are due
 to biological causes4 ,the most common 
defect known is that usually referred to
 as rancidity4 ,there are1 however1     
different types of changes that are     
probably included under this head and it
 is very probable that different causes 
are operative in their production4 ,true
 rancidity is probably due to biological
 causes2 the so-called tallowy change1  
in which the butter acquires the odor of
 tallow is probably due to the combined 
action of light and air on the fat4     

,bacterial defects in butter4 ,there are
 a number of defects in butter that are 
positively known to be due to the growth
 of bacteria in the milk or cream1 or in
 the butter itself4 ,the lack of flavor 
is looked upon as a defect in the case  
of ripened-cream butter4 ,it may be due 
to insufficient ripening of the cream1  
or to the lack of acid-forming bacteria 
that produce the desirable              
flavor-forming compounds4 ,not all      
acid-forming bacteria are able to       
produce favorable1 flavor-giving        
compounds2 hence1 sour cream butter may 
sometimes be deficient in flavor by     
reason of this fact4  ,putrid butter4   
,this specific butter trouble has been  
observed in ,denmark1 where it was first
 studied by ,jensen4 ,butter affected by
 it rapidly acquires a peculiar putrid  
odor that ruins it for table use4       
,sometimes this flavor may be developed 
in the cream previous to churning4 ,it  
may be caused by a number of bacteria4  
,turnip flavored butter4 ,butter        

sometimes acquires a flavor resembling  
turnips4 ,this trouble may be due to the
 feeding of such roots1 the aromatic    
substances peculiar to them being       
absorbed directly by the milk and thus  
transferred to the butter4 ,weigmann    
traced a similar flavor to certain      
bacteria that entered the milk from barn
 filth4  ,cowy odor in butter4 ,there is
 sometimes to be noted an odor in butter
 as in milk that resembles that of the  
cow stable4 ,usually this defect has    
been ascribed to the absorption of these
 odors directly by the milk4 ,organisms 
have also been described that impart to 
the butter a very similar odor4 ,bitter 
butter may be due to the feed that is   
consumed by the cow1 or it may be due to
 those forms of bacteria that produce a 
bitter fermentation of the milk4  ,other
 abnormal flavors4 ,among the numerous  
abnormal flavors that have been noted in
 butter is one of quite frequent        
appearance1 the so called fishy flavor4 
,it is now believed by many that this   

flavor is due to the presence of small  
amounts of iron or copper salts that    
have been introduced into the milk from 
utensils from which the protective      
coating of tin has been worn4 ,if the   
milk or cream stored in such utensils   
develops any marked degree of acidity1  
the acid will dissolve a small amount of
 the iron or copper4 ,the fishy flavor  
has not been found in sweet-cream butter
 as would be expected from the above    
explanation4 ,in fresh butter a metallic
 taste is sometimes present4 ,it is     
believed by some that on storage this   
flavor changes to the fishy flavor4     
,all utensils used for the storage of   
milk and cream should be kept in good   
condition so as to prevent the acid milk
 or cream from coming in contact with   
iron or copper4  ,illustration3 ,fig4   
#cc4--,moldy ,butter4  ,the mold grows  
on the paper in which the butter is     
wrapped rather than on the butter4 ,the 
print on the left was wrapped in the    
same paper as the print on the right    

except that the parchment cover had been
 steamed for a few moments4  ,moldy     
butter4 ,a defect that causes a great   
amount of loss is the development of    
mold on the surface of the butter1      
either in tubs or in prints4 ,this      
trouble is easily prevented4 ,butter is 
not well suited to the growth of mold1  
but the paper used for lining the tubs1 
or wrapping the prints is an excellent  
medium for mold growth4 ,the wood of the
 tub also furnishes ample food for this 
type of life1 especially where the wood 
contains any sap4 ,one other essential  
condition for mold growth is a supply of
 oxygen4 ,the mold spores are widely    
disseminated1 and are always to be found
 on the butter tubs and on the paper4   
,the number is not likely to be         
sufficient to cause trouble unless the  
tubs and paper have been kept under such
 conditions1 as to allow growth to take 
place on them before use4 ,during damp1 
hot weather1 the amount of moisture     
absorbed by these materials is often    

sufficient to allow molds to grow on    
them4 ,this trouble can be prevented by 
the storage of tubs and paper in a clean
 dry place1 or by a disinfecting        
treatment which will destroy the mold   
spores4 ,the most successful method of  
treatment of tubs is to apply paraffin  
to the inner surface1 which can be      
easily done by the use of some one of   
the various machines now on the market4 
,the thin layer of paraffin excludes the
 moisture from the wood1 and also       
prevents the mold from obtaining a      
supply of oxygen for its growth4 ,the   
tubs may be steamed1 treated with hot   
water1 or filled with a dilute solution 
of formaldehyde1 and allowed to stand   
overnight4 ,soaking in brine as is      
usually done in the creameries is of    
some effect1 but will not completely    
kill mold spores4  ,illustration3 ,fig4 
#cd4--,moldy ,butter4  ,the butter was  
placed in a paraffined tub1 but the     
paper was not treated so as to destroy  
the mold spores thereon4  ,butter may   

mold where the tubs have been thoroughly
 treated1 because of the mold spores on 
the paper used for the lining4 ,one of  
the black molds is able to thrive on    
parchment paper whenever the air is     
damp4 ,in the past but little attention 
has been paid to the paper as a source  
of trouble4 ,it is certain that it is   
often at fault1 and that as much        
attention should be paid to the paper as
 to the tub4 ,a most efficient way of   
treating paper1 either for tub liners or
 print wrappers is to place same in     
boiling water for a few minutes4        
,,chapter ,,viii4  ,,bacteria ,,and     
,,cheese ,,making4   ,butter1 such as   
that of the sweet-cream type that is    
highly esteemed in many parts of the    
world1 may be made without the aid of   
bacteria1 but no important kind of      
cheese can be made under commercial     
conditions without them4  ,types of     
cheese4 ,cheese consists of the fat and 
the precipitated casein of milk1        
together with a large amount of water   

and the salts found in milk4 ,the       
numerous types of cheese may be divided 
into two groups1 depending on the manner
 in which the curdling of the milk is   
brought about4 ,sour-milk cheese is made
 from curd1 formed as a result of the   
acid fermentation of the milk4 ,thus1 at
 the very first stage in the making of  
this type1 the importance of bacteria is
 apparent4  ,the second type is that    
made from curd1 which is precipitated by
 the addition of rennet to the milk4    
,this type may also be divided into two 
groups1 depending upon their texture2   
the hard cheese1 and the soft cheese4   
,the ordinary cheddar1 the common       
,american type1 is the most important   
example of the hard cheese2 ,limburger1 
of the soft cheese4 ,cheese are         
designated as hard or soft1 depending   
upon the amount of whey that is retained
 in them during the making process4 ,the
 moisture content has an important      
influence on the type and amount of life
 that develops on and in the curd mass1 

and as will be seen1 the ripening and   
flavor of the cheese are dependent upon 
these biological factors4  ,the two     
groups of hard and soft cheese have no  
sharply defined limits1 but merge into  
each other4 ,the extreme types of the   
hard cheese are so dry and firm that    
they can be cut only with difficulty4   
,such cheese are used primarily as      
condiments to impart a flavor to certain
 dishes1 as macaroni1 and for this      
purpose are grated4 ,the extreme type of
 soft cheese is a soft1 pasty mass and  
can be easily spread with a knife4      
,hard cheese1 because the ripening      
process goes on uniformly throughout the
 entire mass of cheese1 may be made of  
any size which permits of commercial    
handling4 ,they can also be kept for    
long periods and preserve their good    
qualities4 ,soft cheese are made in     
small sizes1 since on account of their  
consistency1 they could not otherwise be
 handled1 and also because of the manner
 of ripening4 ,the ripening is due to   

the action of organisms developing on   
the surface1 the by-products of which   
diffuse into the curd4 ,if the cheese   
are too large1 the outer layers become  
overripe1 while the interior remains    
more or less unchanged1 or              
insufficiently changed4 ,soft cheese    
mature much more rapidly than hard      
cheese2 consequently they are short     
lived4  ,although made from the same    
substance1 milk1 it is noteworthy that  
there are over four hundred varieties of
 cheese produced4 ,most of these find   
only a local market where made4 ,less   
than a dozen varieties are to be        
regarded as general articles of         
commerce4  ,quality of milk4 ,in the    
making of butter there are a number of  
processes that the maker can use when he
 finds himself obliged to utilize poor  
milk4 ,the milk can be pasteurized and  
the harmful bacteria thus destroyed2    
desirable kinds can then be added in the
 form of a pure-culture starter4        
,pasteurization also drives off some of 

the volatile by-products of the first   
acid fermentation4 ,by the use of these 
means1 the maker can prepare a very good
 product from poor material4  ,in the   
making of most kinds of cheese1         
especially those of the greatest        
commercial importance1 the cheese maker 
can call to his help no such aids1 but  
must use the milk as it is brought to   
him4 ,it is possible to prepare certain 
kinds of soft cheese from pasteurized   
milk that differ in no essential point  
from the same cheese made from raw milk4
 ,hard cheese are also made from        
pasteurized milk1 but in most cases such
 cheese differ1 especially in the degree
 of flavor1 from that made from unheated
 milk4 ,it is quite probable that1 as   
the factors concerned in the ripening of
 cheese become better known1 methods    
will be evolved for the successful      
production of many kinds of cheese from 
pasteurized milk4  ,it has been shown   
that the quality of milk is almost      
wholly dependent upon the number and    

kinds of bacteria it contains4 ,these   
bacteria pass into the cheese1 and there
 produce the same products as they would
 have done in the milk itself4 ,in      
butter making1 practically all processes
 are under the control of the maker1    
until the product is ready for the      
market2 but cheese1 on the other hand1  
passes through a complicated series of  
changes after it has left the maker's   
control4 ,during the manipulation of the
 milk and the curd in the vat1 he can   
exert some influence on the quality of  
the product1 but he is much more        
dependent on the quality of the milk    
than is the case in butter making4      
,every effort should therefore be made  
to furnish to the cheese maker the      
quality of milk from which he can       
prepare fine cheese4 ,in other words1   
the milk should be produced under clean 
conditions and carefully cooled and     
handled until delivered to the maker4   
,poor milk from a single farm may have  
such an effect upon the cheese made from

 the milk of twenty farms as to         
depreciate the selling value of the     
entire product several cents per pound4 
,the tests that have been previously    
described 7p4 #aje7 have been devised   
especially for testing the quality of   
the milk for cheese making purposes1 and
 are of the greatest service to the     
maker in tracing the source of poor     
milk4  ,cheddar cheese4 ,the first step 
in the making of cheddar cheese is the  
ripening of the milk1 or the development
 of a small amount of acid4 ,in this    
fermentation1 the development of acid is
 preceded by an enormous increase in the
 number of acid-forming bacteria4 ,milk 
for cheese making should show an acidity
 of about #j4b per cent or slightly more
 than in fresh milk4 ,in other words1   
the maker wishes the milk to be in such 
condition1 bacteriologically1 that if   
kept at a temperature favorable for the 
growth of the acid-forming bacteria1 the
 acidity will increase rapidly4  ,the   
curdling of the milk to precipitate the 

cheese solids is produced by the        
addition of rennet1 which is obtained by
 extracting the fourth stomach of the   
young calf with a solution of common    
salt4 ,in the past the maker prepared   
his own rennet solution from the dried  
stomachs 7rennets71 but at present1 the 
extract is prepared commercially1 in a  
much more uniform manner4 ,the rapidity 
of the curdling is dependent upon the   
acidity of the milk4 ,in order to secure
 proper rennet action1 a slight increase
 of acid over that found in fresh milk  
is usually necessary2 thus at the very  
beginning of the process of making      
cheddar cheese1 the bacteria are of     
importance4  ,as the milk curdles1 the  
bacteria are enclosed in the curd as are
 the fat globules4 ,the curd is cut into
 small fragments by means of a curd     
knife1 and as the mass is warmed1 the   
acid develops1 causing the curd         
particles to shrink1 thus expressing the
 whey4 ,within a short time1 the volume 
of the curd is not more than one-eighth 

that of the milk1 but in the curd are   
held over #ge per cent of the bacteria  
of the milk4 ,to secure rapid curdling  
in the vat1 the milk is warmed to #he to
 #ij ,f41 a temperature that is most    
favorable for the growth of the lactic  
bacteria4 ,since there is a large number
 of bacteria concentrated in a small    
volume1 and the temperature1 as well as 
all other conditions1 is favorable to   
growth1 multiplication of the bacteria  
goes on rapidly1 and as a consequence1  
acid is formed in large amounts1 as is  
shown by the following figures given by 
,publow for the manufacture of the      
export type of cheddar cheese3          
,acidity of milk before adding rennet   
4#b  to 4#ba per cent   ,acidity of whey
 before heating curd                4#ad
 to 4#ade       ,acidity of whey before 
removing from curd          4#af to 4#ah
        ,acidity of whey coming from the
 curd after     removal of whey and curd
 is packed               4#bd to 4#cj   
,acidity of whey coming from curd before

 milling    4#fe to 4#ge        ,acidity
 of whey coming from curd before salting
    4#ij to #a4aj      ,if the milk had 
been kept at the same temperature as the
 curd1 the acidity would have increased 
much more slowly since the acid would   
have been distributed through a larger  
volume4 ,in the cheese curd the same    
amount of acid is probably formed1 as   
would have been produced in the total   
amount of milk during the same interval4
  ,the acid produced by this bacterial  
activity has a most marked effect on the
 curd4 ,at first the curd masses are    
tough and firm1 the particles showing no
 tendency to adhere to each other4 ,as  
the acid increases in amount1 the curd  
becomes plastic1 the outer surface of   
the particles adhering or matting1 as   
the maker expresses it4 ,the result is a
 solid coalescent mass of curd1 which is
 cut into small pieces1 i4e41 milled1   
before it is put to press4 ,the acid    
allows the blending of the pieces under 
the influence of the pressure so that a 

cheese is one single mass4 ,under       
certain abnormal conditions1 the        
development of acid may be interfered   
with and the particles of curd fail to  
mat1 in which case1 the cheese will be  
crumbly when it is cut4 ,the            
determination of the proper time for    
pressing is made by the application of  
what is known as the hot iron test4     
,this is made by determining the length 
of the strings or threads which can be  
drawn from a mass of curd when it is    
brought in contact with a hot iron at a 
cherry red heat1 the length of the curd 
threads being a measure of the amount of
 acid that has been formed in the curd4 
,the rate of acid formation within the  
curd particles is also measured by      
determining the acidity of the whey as  
it comes from the curd at different     
stages in the making4 ,this test1 which 
is often used in place of the hot iron  
test is carried out in the same manner1 
as in determining the acidity of milk or
 cream4 ,the quality of the cheese1 both

 as to texture and flavor1 is dependent 
to a great degree upon the amount of    
acid that is formed during the various  
stages in making2 hence1 the successful 
maker must follow closely by some means 
the acid formation in the curd until it 
is put to press4  ,it is very necessary 
that the milk shall contain a sufficient
 number of acid-forming bacteria to     
produce the required amount of acid4 ,if
 a sufficient number of bacteria are not
 present in the milk as it is received1 
as is the case with very sweet milk1    
they must be added by the maker in the  
form of a starter1 or the process of    
making will be much prolonged4          
,illustration3 ,fig4 #ce4--;,bacteria in
 ,cheese4  ,a photomicrograph of curd   
just after curdling has taken place4    
,note the few lactic acid bacteria      
embedded in the curd4  ,starters in     
cheese making4 ,the starters used in    
cheese making1 are identical with those 
employed in butter making and the same  
precautions should be observed in their 

propagation4 ,it is important that the  
starters should not be such as to form a
 hard curd that cannot be mixed         
uniformly with the milk1 since the curd 
particles would appear as white specks  
in the cheese4 ,the starter should be   
added to the milk through a hair sieve1 
and well mixed with the milk1 so as to  
distribute the bacteria uniformly4      
,amounts varying from #j4e to #b per    
cent are used4 ,in butter making1 it is 
essential that the bacteria of the      
starter be able to form not only acid1  
but sufficient flavor-forming substances
 to impart to the butter a desirable    
flavor4 ,in cheese making it is not     
probable that this latter characteristic
 is of any particular importance4       
,illustration3 ,fig4 #cf4--;,bacteria in
 ,cheese4  ,a photomicrograph of curd at
 the time the salt is added4 ,the lactic
 acid bacteria have increased materially
 in numbers4  ,it is desirable that the 
process of cheese making shall conform  
as closely as possible to that which    

experience has shown to give the best   
results4 ,the rate at which acid is     
developed in the curd and the rapidity  
with which the whey is expelled         
therefrom should bear a certain ratio to
 each other4 ,if the milk has too high a
 degree of acidity1 i4e41 is overripe1  
the acidity developed in the curd will  
be too high before the curd is          
sufficiently firm2 with a very sweet    
milk1 the reverse may be true4 ,it is   
desirable for the cheesemaker to obtain 
as good an idea as possible of the      
condition of the milk with reference to 
its bacterial content1 since this will  
determine the rate at which acid will be
 formed in the curd4 ,if the milk is too
 sweet1 i4e41 too low in acid-forming   
bacteria1 a starter should be added4    
,the only methods by which this         
information can be obtained by the maker
 is by determining the acidity by the   
usual method or better by the use of the
 rennet test by which is ascertained the
 time required for a given amount of    

rennet to curdle a definite quantity of 
milk at a standard temperature4 ,the    
varying factor in the test will be the  
acidity of the milk4 ,very slight       
differences influence profoundly the    
time of curdling4 ,if1 working under    
standard conditions1 it is found that   
the time of curdling of one sample is   
#aj seconds and of another sample1 #bj  
seconds1 it is proof that the acidity of
 the first is higher than that of the   
second1 that its bacterial content is   
greater and that acidity will develop in
 the curd more rapidly4 ,the first may  
need a small amount of starter1 the     
second a larger quantity4 ,working with 
milk from the same source1 the maker1   
from his experience1 will know how much 
starter should be added to milk that has
 given a certain result with the rennet 
test in order that the acid shall be    
developed in the curd at a desired rate4
  ,ripening of cheese4 ,the curd at the 
time it is put to press is tough and    
rubbery1 and has none of the            

characteristic flavor of cheddar cheese2
 it is also quite insoluble and         
indigestible4 ,before the cheese is fit 
to eat it must pass through a complex   
series of changes which are collectively
 known as ripening4 ,in these changes   
there is not only a breaking down of the
 casein into soluble compounds1 which   
process makes the cheese soft and       
plastic under pressure1 but the         
characteristic flavor is developed in   
greater or less degree4 ,a very         
considerable part of the cheese thus    
becomes soluble in water1 and it is much
 more easily digested than in an        
unripened condition4  ,the different    
factors that are operative in the       
ripening changes are not yet fully      
known1 but in recent years as a result  
of scientific study1 material progress  
in the study of the changes has been    
made4  ,rennet4 ,the commercial rennet  
extract when in condition for use       
contains very few bacteria4 ,a          
preservative1 boric acid1 is added by   

the manufacturer to restrain the        
bacteria1 otherwise the extract would   
soon be unfit for use4 ,the bacteria in 
the commercial rennet extract are too   
few to be of any importance whatever in 
the ripening process4  ,rennet extract  
contains an enzyme1 rennin1 that causes 
the milk to curdle2 also another enzyme1
 pepsin1 that exerts a digestive action 
on the curdled casein4 ,pepsin is always
 found in the stomach juices of all     
animals1 but no digestive action takes  
place1 unless the reaction is distinctly
 acid1 as is the ease under normal      
conditions1 since hydrochloric acid is  
excreted by the walls of the stomach4   
,outside of the stomach1 the same       
conditions must obtain with reference to
 the presence of acid1 if pepsin is to  
exert a digestive effect4 ,in the cheese
 curd1 the milk sugar is rapidly changed
 into lactic acid by the action of the  
bacteria4 ,this gives the proper        
chemical reaction for peptic action1 and
 the enzyme is then able to act on the  

paracasein1 the nitrogenous part of the 
cheese4 ,if milk contains no            
acid-forming bacteria1 conditions will  
not permit of peptic action1 and as a   
consequence1 the ripening processes do  
not take place4 ,if the sugar is        
fermented by some organism that does not
 form acid1 as the lactose-fermenting   
yeasts1 the cheese does not ripen4 ,the 
lactic bacteria are therefore an        
essential factor in inaugurating the    
ripening changes in all types of rennet 
cheese4  ,preservative action of acid4  
,in a previous chapter it was shown that
 raw milk does not undergo putrefaction 
because of the restraining effect of the
 acid formed by the lactic bacteria on  
the putrefactive organisms4 ,this same  
phenomenon is noted in cheese4 ,milk    
always contains putrefactive bacteria   
which pass into the cheese1 but they    
cannot grow therein because of the high 
acidity4 ,in the absence of the         
acid-forming organisms in the cheese1   
the cheese may remain tough and rubbery1

 on account of the lack of suitable     
conditions for the action of the pepsin 
of the rennet extract1 or when the milk 
contains large numbers of digesting     
organisms1 the cheese may develop a     
putrefactive condition1 as noted by the 
offensive odor and soft pasty texture4  
,other factors concerned in cheese      
ripening4 ,there are other factors that 
are also concerned in the complex series
 of ripening changes noted in cheddar   
cheese4 ,all animal fluids and tissues1 
if kept under perfectly sterile         
conditions at ordinary temperatures1    
will undergo a certain amount of        
decomposition1 due apparently to their  
content in enzymes that have a digestive
 action4 ,meat kept in storage becomes  
more tender due to the softening of the 
connective tissue4 ,milk1 derived as it 
is from actively secreting cell tissue1 
gives certain reactions that are common 
to living material4 ,if chloroform1     
which restrains the action of bacteria1 
but does not prevent the activity of    

enzymes1 is added to it1 it will curdle 
in the course of a few weeks and will   
become partially digested4 ,this        
digesting ferment found in milk is known
 as galactase4 ,compounds are formed in 
milk thus preserved that are similar to 
those found in a ripe cheddar cheese4   
,many experiments have been made with   
pasteurized milk1 but it has not been   
possible to produce typical1 normal     
cheese from thoroughly pasteurized milk4
 ,such cheese are markedly deficient in 
the typical flavor of cheddar cheese4   
,from this fact it is believed that the 
inherent enzymes of milk are a factor of
 some importance in the ripening of this
 type of cheese at least1 if not of all 
types4  ,in the past1 other factors have
 been thought to be of importance4      
,duclaux1 a ,french bacteriologist1     
considered that the enzymes formed by   
the digesting bacteria are responsible  
for the ripening4 ,it is now known that 
they can have but little if any part in 
the process1 since they are not present 

in all cheese in sufficient numbers to  
have any marked effect1 and since the   
acidity of the cheese mass will not     
permit of their development4  ,other    
types of bacteria have been considered  
by bacteriologists to be of importance  
in the ripening process1 but it is      
certain that the purely digestive change
 in the mass of the cheese can be       
accounted for through the action of the 
factors already noted4  ,flavor         
production4 ,the flavor of any type of  
cheese is the most important            
characteristic1 just as it is in butter1
 for it is largely the flavor that      
determines the selling value of the     
product1 and is the most difficult thing
 to control4 ,it has been thought that  
the flavor-producing substances were    
derived from the paracasein of the curd 
and were produced by the factors that   
are concerned in the digestion of the   
paracasein4 ,it has been shown that a   
cheese may be thoroughly ripened as far 
as its physical properties are          

concerned2 that it may contain the end  
products of casein digestion1 and yet be
 low in flavor4 ,from recent researches 
it seems probable that the production of
 flavor is connected with the change    
that the sugar undergoes in the acid    
fermentation1 as volatile acids1 acetic1
 formic1 etc41 as well as alcohols and  
esters are formed in increasing amounts 
as the ripening progresses4 ,these may  
have come from the decomposition of the 
milk sugar1 or from a secondary change  
in the products of the lactic           
fermentation4 ,there are organisms in   
both milk and cheese that do not grow on
 the ordinary culture media used by the 
bacteriologist1 and it may well be that 
some of these are of importance in      
flavor production4 ,their destruction in
 pasteurization is likely to be one of  
the reasons for the failure of cheese   
made from pasteurized milk to develop   
typical flavor4  ,effect of temperature 
on ripening4 ,the temperature at which  
the ripening cheese is kept has been    

found to be of the greatest importance  
in determining the quality of the       
product4 ,if the cheese is kept at high 
temperatures1 the ripening proceeds     
rapidly2 the cheese is short lived1 and 
has a sharp1 strong flavor1 and         
generally a more or less open texture4  
,unless the cheese is made from the best
 quality of milk1 it is likely to       
undergo undesirable fermentations when  
ripened at high temperatures4  ,within  
recent years it has been found possible 
to ripen cheese at temperatures that    
were previously thought to be certain to
 spoil the product4 ,much of the cheese 
is now ripened at temperatures below #ej
 ,f4 ,the ripening goes on more slowly  
than at higher temperatures1 but the    
flavor of the cheese is clean and       
entirely devoid of the sharp undesirable
 tang that is so frequently noted in old
 cheese1 and the texture is solid and   
meaty4 ,ripening at low temperatures1   
when the milk is not of the best        
quality1 is certain to result in a much 

better product than when higher         
temperatures are employed4  ,abnormal   
fermentations in cheese4 ,as has been   
previously shown1 it is necessary to    
have an abundant supply of acid-forming 
bacteria in the milk from which cheese  
is to be made4 ,if these bacteria are   
supplanted by other kinds1 the product  
will be more or less abnormal either in 
texture or in flavor1 or possibly in    
both4 ,many of these abnormal           
fermentations have been studied and the 
organisms concerned in the changes      
found4  ,if the milk is handled         
carelessly1 it will contain many        
bacteria able to form acid and gas4 ,as 
noted previously1 these organisms form  
products in milk that have an offensive 
odor and a disagreeable taste4 ,in      
cheese the gases cause the formation of 
holes1 more or less numerous1 depending 
on the number of the gas-forming        
bacteria in the milk4 ,where these      
bacteria are abundant1 gas may appear   
while the curd is in the vat1 causing it

 to float in the whey1 when it is known 
as a floater4 ,again1 the gas may not   
become evident until the cheese is in   
the press or on the curing shelf1 when  
it becomes apparent by the swelling or  
bulging of the cheese4 ,such cheese is  
termed huffed or swelled4 ,the internal 
pressure may be so great as to cause the
 cheese to crack and to force out some  
of the curd4 ,the presence of gas holes 
is indicative of a poor cheese1 because 
the formation of gas is always          
accompanied by the presence of other    
undesirable compounds4  ,pure culture   
starters are often used to overcome     
gassy fermentations4 ,in cheese a       
certain amount of acid can be produced  
by the acid-forming bacteria4 ,when the 
pure lactic bacteria alone are present1 
the cheese is very likely to be of good 
quality4 ,if the sugar is fermented by  
gas-forming organisms1 the curd will be 
full of holes and the flavor poor1 while
 if the sugar is fermented by a mixture 
of the desirable and undesirable        

bacteria1 the quality of the product    
will depend on the relation of the two  
types4 ,if through the addition of a    
pure-culture starter1 the proportion of 
desirable bacteria is increased1 the gas
 will be lessened in amount and the     
cheese improved4 ,it was formerly       
supposed that the lactic bacteria had an
 injurious effect on the gas-forming    
organisms4 ,there is no good reason to  
believe that this is the case1 but that 
both grow in the milk and cheese1 but   
since only a certain amount of acid can 
be produced1 it is important to have as 
much of it formed by the lactic bacteria
 as possible1 since the amount of       
injurious products in the cheese will   
thus be limited4  ,illustration3 ,fig4  
#cg4--;,gassy ,cheese4  ,such a cheese  
is worthless on account of its poor     
flavor4 ,the irregular holes are        
mechanical4 ,the crack on the upper side
 is due to the pressure of the gas which
 has caused the cheese to bulge at this 
point4  ,the gas formed in the curd     

before the cheese is put to press can be
 gotten rid of by proper manipulation of
 the curd4 ,while this treatment may    
improve the appearance of the cheese1 it
 does not eliminate the substances that 
impart to the cheese undesirable        
qualities4  ,gassy curds have also been 
treated by washing the curd with cold   
water4 ,care must be taken in applying  
this method for the removal of too much 
of the sugar and acid from the curd by  
the washing will permit the growth of   
injurious forms of bacteria4 ,the       
addition of salt or of saltpeter has    
also been made to the milk in order to  
overcome gassy conditions in the milk4  
,in the handling of gassy milk1 the     
usual practice has been to develop a    
larger amount of acid before drawing the
 whey than in the case of good milk4    
,this was done with the idea that acid  
suppressed gas formation4 ,it has been  
shown previously that this is not the   
case4 ,it has also been shown by ,doane 
that the development of too much acid   

before drawing the whey is likely to    
result in undesirable flavors1 producing
 what is known as high-acid or sour     
cheese4  ,the gas-forming bacteria grow 
best at high temperatures2 hence1 cheese
 kept under these conditions are more   
likely to be affected by this trouble   
than are those kept at lower            
temperatures4  ,the most successful     
method of preventing trouble with gassy 
milk in cheese making is to eliminate   
undesirable milk by frequent testing of 
the supply of the different patrons by  
means of the ,wisconsin curd test4  ,not
 only gas-forming bacteria may be the   
cause of gassy cheese1 but the          
lactose-fermenting yeasts may cause     
similar trouble4 ,if these are abundant 
in the milk1 a considerable part of the 
sugar may be fermented by them1 in which
 case1 carbon dioxide gas is abundantly 
formed4 ,the cheese thus rendered gassy 
will present the same appearance to the 
eye as where the gas is formed by       
bacteria1 but will have a different     

flavor4 ,the odor of alcohol may be     
evident1 and if most of the sugar has   
been fermented by the yeast1 the acidity
 of the cheese may not be sufficient for
 the pepsin to exert its digestive      
action4  ,milk containing many          
gas-forming bacteria occurs most        
frequently in summer4 ,it is claimed by 
some that the milk of cattle pastured on
 low lands is more likely to contain the
 gas-forming organisms than that from   
cattle running on higher lands4 ,if this
 is true1 it must be due to the         
bacterial content of the soil2 the      
udders of the animals become soiled as  
they lie on the ground1 and during the  
milking1 the dust finds its way into the
 pail4 ,many cheese makers think that   
the milk from an animal suffering from a
 garget may be the cause of the huffing 
of cheese4 ,this belief is undoubtedly  
well founded1 as some of the bacteria   
known to be the cause of garget are     
gas-forming4  ,bitter cheese4 ,in a     
previous chapter the bitter fermentation

 of milk has been discussed4 ,if milk   
containing large numbers of such        
organisms is made into cheese1 the      
bitterness is very likely to be noted in
 it4 ,cheese made from milk containing  
few or no lactic bacteria is likely to  
develop a bitter taste1 due to the      
growth of the digestive bacteria that   
are able to grow through the lack of    
acid in the cheese4  ,if the milk       
contains considerable numbers of yeasts1
 a sweet or fruity flavor is apt to     
develop1 due to the products of the     
fermentation of the sugar by the yeast4 
,this flavor resembles that of fermented
 fruit1 or the bouquet of certain kinds 
of wine4  ,putrid cheese4 ,in the       
absence of acid-forming bacteria1 the   
cheese may develop a putrid or rotten   
odor1 due to the growth of some types of
 putrefactive or digesting bacteria4    
,this trouble is very infrequent in     
cheddar cheese1 since this is made from 
ripened milk1 but occurs more frequently
 in those types in which no acid is     

developed4  ,bacteria develop in the    
cheese in colonies or masses1 just as   
they do in the plate cultures of the    
bacteriologist1 made with transparent   
media1 such as gelatin4 ,cheese is      
opaque2 therefore1 the growing colonies 
cannot be readily discovered1 but when  
pigment-forming bacteria grow in the    
cheese1 their presence is likely to be  
noted1 because of the colored spots that
 are formed4  ,rusty spot4 ,the rusty   
spot that has been encountered in ,new  
,york and ,canada is due to one of the  
colored bacteria which produces an      
orange or yellowish-red pigment4        
,various other pigment-forming organisms
 have been met in cheese1 each producing
 its colored colony which differentiates
 itself from the mass of the cheese4 ,if
 the pigment is produced in considerable
 quantities1 and is soluble in any of   
the constituents of the cheese1 the     
color will not appear in spots but will 
be more diffuse1 or may impart a color  
to the entire mass4  ,cases of acute    

poisoning arising from the ingestion of 
cheese are not infrequently reported2   
similar instances result from the use of
 ice cream4 ,in both cases it is        
believed that poisonous products have   
been formed by bacteria1 probably by    
some of the putrefactive forms4  ,from  
what has been said with reference to the
 abnormal fermentations of cheese1 it   
will be seen that they are always due to
 the lack of acid-forming bacteria1 or  
to their partial replacement by other   
types4 ,in order to prevent such        
troubles1 it is necessary to insure that
 the milk has been produced under clean 
conditions1 from healthy cows1 and has  
been handled in such a manner as to     
reach the maker in as sweet and fresh   
condition as possible4 ,the maker can1  
by the use of proper starters1 control  
the kinds of bacteria essential for the 
ripening process4 ,a well trained maker 
should be able to prepare from such milk
 a uniform product of the highest       
quality4 ,the effort of cheese makers at

 the present time is to handle milk of  
more or less objectionable quality so as
 to secure from it as good cheese as is 
possible4 ,but cheese is so sensitive as
 to character of milk used that greater 
effort should be spent in securing an   
improved supply4  ,moldy cheese4 ,in the
 case of the cheddar cheese and other   
types of hard cheese1 it is essential   
that their surfaces be kept clean1 and  
not discolored by the growth of molds1  
which find favorable conditions for     
growth on the surface of the cheese in  
the moist atmosphere of the curing room4
 ,the molding of cheddar cheese can be  
prevented by covering the cheese with a 
layer of paraffin which stops the       
development of the mold spores1 by      
shutting off the necessary supply of    
oxygen4 ,for this purpose the cheese are
 dipped in melted paraffin when a few   
days old4  ,in the case of types of     
cheese which are salted by applying the 
salt to the surface1 or with soft cheese
 which ripen from the outside1 other    

methods of mold prevention are employed1
 such as rubbing and washing the cheese4
 ,the curing room itself may be freed   
from the mold spores by the use of such 
standard disinfectants as formalin or   
sulphur4  ,swiss cheese4 ,one of the    
most important kinds of hard cheese1 is 
the ,swiss or ,emmenthaler1 so named1   
from the country and valley in which the
 cheese was first made4 ,in ,america1   
this type was introduced by ,swiss      
immigrants1 and is being made in        
constantly increasing quantities in     
,ohio and ,wisconsin4  ,swiss cheese is 
a hard firm type1 appearing in the      
markets in the form of the flat circular
 drum cheese1 two to three feet in      
diameter1 and six to eight inches thick1
 or in the smaller block form4 ,in this 
country the cheese is prepared twice a  
day1 since it is necessary to work up   
the milk while it is perfectly sweet4   
,indeed1 the milk is received at the    
factories while it is still warm1 and   
within five or six hours after it is    

drawn from the cow the cheese is on the 
press4 ,if the attempt is made to       
prepare ,swiss cheese from the kind of  
milk that is best suited for cheddar    
purposes1 i4e41 milk in which the       
acidity has increased to some extent1   
the flavor of the resulting product is  
likely to approximate a cheddar cheese  
rather than that of a ,swiss4  ,in the  
salting process1 the salt is not mixed  
with the curd before it is pressed1 but 
is applied by immersing the cheese for a
 few days in a saturated brine1 and then
 rubbing salt over the surface of the   
cheese4 ,in this way the salt gradually 
diffuses quite uniformly through the    
cheese4 ,the method of salting has      
apparently a marked influence on the    
ripening process1 since if the salt is  
added in the same way1 and in amounts   
used in the cheddar process1 the flavor 
will not be that of a ,swiss cheese but 
will resemble a cheddar4  ,in cheddar   
cheese1 the whey is expelled from the   
curd by means of the acid which is      

developed in the curd1 and by heating   
the curd to a temperature of #ie ,f4 to 
#ajj ,f4 ,in ,swiss cheese the          
development of acid during the making   
process is prevented1 because of the    
smaller number of acid-forming bacteria 
in the milk2 other factors must         
therefore contribute to the expulsion of
 the whey to secure a firm curd4 ,this  
is accomplished by cutting the curd into
 very small pieces and by briskly       
stirring it during the making1 heating  
it during this process for a period of  
#bj to #cj minutes at #acj to #adj ,f4  
,it might be thought that this high     
temperature1 which is approximately that
 used in pasteurization would destroy   
the acid-forming bacteria1 but these are
 apparently protected as they are within
 the curd4 ,during the time the cheese  
is being pressed1 the contained bacteria
 begin to grow and the whey coming from 
the cheese toward the end of the        
pressing shows a high acidity4 ,if it   
does not show such a development of     

acid1 the maker has reason to believe   
that the cheese may never ripen in a    
typical manner4  ,it has been mentioned 
that the milk contains but few          
acid-forming bacteria4 ,the maker1      
however1 attempts to insure the presence
 of a sufficient number by the use of   
home-made rennet4 ,this is prepared by  
placing a piece of dried rennet1 i4e41  
the stomach of the calf1 in whey1       
keeping the same in a warm place for    
twenty-four to thirty-six hours4 ,as the
 rennet contains acid-forming organisms1
 these grow rapidly in the warm whey1 so
 that by adding this sour whey to the   
milk1 the maker is not only adding      
rennet1 that is to curdle the milk1 but 
also a small starter of lactic bacteria4
 ,if the rennet thus prepared contains  
no harmful bacteria and the milk is of  
good quality1 the cheese is likely to   
ripen in a normal manner4 ,the rennet   
should be prepared with due regard to   
bacteriological principles1 a condition 
that is rarely met in ,swiss factories  

in this country4  ,swiss cheese has two 
striking characteristics1 the flavor and
 the presence of holes or eyes4 ,the    
flavor is sweetish rather than the sharp
 and pungent flavor of cheddar cheese4  
,the bacteria concerned in its          
production are not known1 but it is     
certain that specific organisms play    
some role1 since if the flora of the    
cheese is changed by salting the curd or
 by the use of milk containing large    
numbers of lactic bacteria1 the flavor  
will also be changed4 ,this role of the 
acid-forming bacteria in ,swiss is the  
same as in cheddar1 i4e41 through the   
acid1 conditions are established for    
peptic action1 the curd being partially 
digested while at the same time the curd
 mass is protected from putrefactive    
processes4  ,in ,swiss cheese during the
 ripening process1 holes about the size 
of a large cherry develop which should  
be quite uniformly distributed          
throughout the cheese4 ,the inner       
surface of the hole is glistening and1  

in a well-ripened cheese1 a small       
quantity of clear brine1 i4e41 tears may
 be noted4 ,these holes or eyes may be  
called the trade mark of the ,swiss     
cheese1 since without them the product  
has a lessened commercial value1 even if
 it possesses the typical flavor4 ,the  
eyes are caused by bacteria that ferment
 the lactic acid produced by the lactic 
bacteria1 forming from it propionic acid
 and carbon dioxide1 the latter gas     
being the cause of the hole or eye4     
,illustration3 ,fig4 #ch4--,swiss       
,cheese4  ,normal development of eyes in
 a ,swiss cheese4 ,the eyes are         
generally as large as a cherry4  ,the   
eye-forming organisms cannot grow in the
 presence of any amount of salt1 hence1 
if salt is added directly to the curd1  
the cheese is likely to be blind or free
 from holes4 ,the eyes are formed not at
 the time gas holes are produced in a   
cheddar cheese1 i4e41 early in the      
ripening process1 but after a lapse of  
three or four weeks4 ,they are most     

abundant in the middle of the cheese    
since the manner of salting is such as  
to inhibit their formation near the     
surface4 ,the eye-forming bacteria may  
have some effect on the flavor of the   
cheese4  ,the ,swiss maker encounters   
the same troubles as does the cheddar   
maker4 ,gassy cheese is more prevalent  
in the ,swiss than in the cheddar       
industry1 since the maker cannot call to
 his aid the methods used by the cheddar
 maker1 viz41 the addition of a heavy   
starter1 the washing of the curd1 etc4  
,it is especially important that the    
quality of the milk be first class in   
every respect1 and yet customs prevail  
in the ,swiss industry that are directly
 inimical to the production of good     
milk4 ,the grossest carelessness        
prevails at the factories in the matter 
of handling the whey4 ,it is often kept 
in individual barrels for each patron4  
7,see ,fig4 #h47 ,these are not kept    
thoroughly clean and the result is that 
the whey taken back to the farm in the  

cans that are used to bring the fresh   
milk is often in an advanced stage of   
fermentation4  ,there are many other    
kinds of hard cheese2 but in each1 so   
far as is known1 the role of the        
acid-forming bacteria is identical with 
that noted in cheddar and ,swiss cheese1
 viz1 in preparing conditions favorable 
for peptic action1 and preventing the   
development of putrefactive bacteria    
present in the curd4  ,roquefort cheese4
 ,among the more important foreign types
 of cheese that are characterized by the
 development of mold is ,roquefort1 so  
named from the district in ,france in   
which it is made4 ,this cheese is made  
from sheep's milk1 in much the same     
manner as cheddar4 ,the characteristic  
process in its preparation is the       
inoculation of the curd1 at the time it 
is put to press1 with the spores of a   
particular kind of mold1 a type closely 
related to the ordinary green mold of   
bread and cheese4 ,the mold for         
inoculation is grown on bread1 the whole

 mass being dried so that it can be     
powdered2 then the ground-up material is
 sprinkled on the curd as it is placed  
in the press hoops4 ,the first stage in 
the ripening of ,roquefort is probably  
identical with that of the types of hard
 cheeses already considered1 the        
breaking-down of the curd being due to  
the pepsin of the rennet used1 which    
action is made possible by the acid     
formed by the bacteria4  ,the second    
stage in ripening1 and one in which the 
characteristic flavor of the cheese is  
developed1 is due to the growth of the  
mold with which the cheese is seeded4   
,molds can grow only in the presence of 
air1 and in order to provide this       
condition1 the cheese are run through a 
machine having a series of needle-like  
projections which fills the cheese with 
fine holes4 ,this allows the air to     
penetrate the cheese and the mold to    
grow1 the fruiting of which develops the
 characteristic flavor4 ,the changes    
produced by the mold are not well       

understood1 but the flavor is evidently 
connected with its development since in 
the absence of mold1 it does not appear4
 ,the cheese must be cured under        
carefully controlled conditions1 as to  
temperature and moisture2 in ,france    
these are secured by curing the cheese  
in limestone caves that are highly      
saturated with moisture4 ,attempts have 
been made to make ,roquefort cheese in  
other parts of the world1 but they have 
never been successful1 due undoubtedly  
to the fact that the proper environment 
and conditions for the development of   
the various types of organisms necessary
 in the ripening process have not been  
met4 ,this cheese is sold for #ej to #ge
 cents per pound in the markets of the  
world4  ,there are two other kinds of   
cheese that are closely related to      
,roquefort1 as to the manner of         
ripening1 viz41 the ,gorgonzola of      
,italy and the ,stilton of ,england1    
both of which possess their             
characteristic flavors by reason of the 

development of molds4 ,in ,stilton      
cheese the mold is not intentionally    
added1 the maker relying on the         
contamination that comes from the       
factory for the usual seeding4 ,if this 
does not develop1 it is sometimes       
inoculated by exchanging plugs with a   
well-ripened ,stilton4 ,this method is  
not so certain as in the inoculation of 
,roquefort4  ,camembert cheese4 ,a      
typical example of soft cheese is one of
 the ,french types1 known as ,camembert4
 ,this cheese is prepared from cow's    
milk which is curdled by rennet4 ,the   
curd is not cut but is dipped into the  
forms1 which condition1 taken with the  
absence of pressure in forming the      
cheese1 accounts for the large quantity 
of whey in it4 ,the finished cheese are 
about one inch in thickness and three   
inches in diameter4 ,in the ripening1   
the moisture and temperature of the     
curing room are very carefully          
regulated4  ,the first stage in the     
ripening is due to the rennet and the   

lactic bacteria4 ,later there appears on
 the surface of the moist cheese1 a     
moldy growth4 ,in this1 there are at    
least two kinds of molds1 the ordinary  
mold that appears on sour milk1 ,oidium 
lactis1 and another that is related to  
the bread mold but which has a white    
instead of a green fruiting stage4      
,these molds are confined to the surface
 of the cheese but the enzymes which    
they produce diffuse into the substance1
 changing the color from a dull1 opaque 
white to a translucent yellow4 ,the acid
 that has been formed by the lactic     
bacteria is gradually used up by the    
growth of the mold1 and conditions then 
become favorable for the growth of      
putrefactive bacteria which digest the  
curd4 ,the cheese is ready for use when 
the action of the mold has penetrated to
 the center of the cheese1 and before   
any pronounced putrefaction has taken   
place4 ,the production of the typical   
flavor is dependent upon there being a  
definite relation between the growth of 

the molds and bacteria4 ,this relation  
is dependent largely upon the moisture  
and temperature of the curing room4     
,these cannot always be regulated with  
exactness2 and hence1 much of this type 
of cheese is not of first quality1 and  
must be sold for a low price4 ,while    
such fancy cheeses1 as ,camembert1 bring
 fifty cents and upward per pound1 and  
the yield from the milk is much greater 
than with the hard type of cheese1 yet  
the difficulties of successful          
manufacture are such as to make success 
less easily attained than with the other
 types4  ,there are many other kinds of 
soft cheese that depend for their       
ripening upon factors similar to those  
concerned in the ripening of ,camembert2
 most of them are1 however1 of small    
importance from a commercial standpoint4
  ,limburger cheese4 ,a very famous     
cheese is one originally made in        
,germany to which the name ,limburger is
 given4 ,it is classed as a soft cheese 
although it is much firmer than         

,camembert4 ,this cheese is made from   
cow's milk and is pressed very lightly  
or not at all1 which condition accounts 
for its high per cent 7#ej per cent7 of 
moisture4 ,the surface is kept moist by 
repeated washing of the cheese1 and by  
keeping the air of the curing room very 
moist4 ,a yellowish1 slimy1 bacterial   
layer soon develops on the surface under
 these conditions4 ,the enzymes produced
 by this external growth gradually      
diffuse to the center of the cheese1    
when it is regarded as ripe4 ,the odor  
of the matured product is somewhat      
putrefactive1 but is not so offensive as
 is usually supposed4  ,definite        
knowledge concerning the types of       
organisms concerned in the surface layer
 is very limited4 ,it is not certain    
whether the same kinds of organisms must
 always be present4 ,limburger is much  
easier to make than ,camembert1 due     
possibly to the fact that there are not 
needed definite forms of life and that  
the balance between them is not so      

delicate4  ,a cheese known as brick is  
closely related to ,limburger in its    
method of making and of ripening but is 
less pronounced in flavor4  ,in the     
manufacture of all of these types of    
cheese1 troubles are likely to develop1 
due to an abnormal bacterial condition  
of the milk4  ,it will be seen from what
 has been said that the bacteria are    
essential factors in cheese ripening1   
and that the cheese industry1 like the  
butter industry1 may be called a true   
fermentation industry4 ,close           
co-operation must exist between the milk
 producer1 and the maker so that the    
type of fermentation that goes on in the
 milk can be controlled4 ,a recognition 
of the fundamental principles governing 
these fermentations1 both normal as well
 as abnormal1 is now regarded as an     
essential part of the training of the   
dairy manufacturer of today4            
,,chapter ,,ix4  ,,bacteria ,,in        
,,market ,,milk4   ,within the last     
decade attention has been especially    

directed toward the quality of milk that
 is furnished to the people in the      
cities4 ,this has come about1 in part1  
in connection with the demands made for 
better and purer food of every kind4    
,these demands are reflected in the     
pure-food laws enacted by the federal   
government1 and by the various states   
and municipalities4 ,another factor that
 has focused attention on the milk      
supplies has been the belief that it    
plays an important role in the          
production and distribution of disease1 
especially among children4 ,the rapid   
growth of cities in all of the great    
countries of the world1 the higher      
standard of living1 and the greater     
demand for milk and other dairy         
products1 has1 of necessity1 widened the
 zone from which the milk supply of any 
particular city must be drawn4 ,milk is 
now an article of export and of import2 
some of the great cities draw a portion 
of their supply from farms hundreds of  
miles away4 ,this means that a longer   

time must elapse between the time of    
production and consumption1             
necessitating the exercise of greater   
care in production and handling in order
 to preserve the milk until it reaches  
the consumer4  ,in the past in the      
cities1 as in the smaller towns at      
present1 the supply was largely         
furnished by the producer directly to   
the consumer4 ,this direct contact      
afforded the consumer the opportunity of
 informing himself of the conditions    
under which his milk supply was produced
 if he desired4 ,the advent of the      
middleman in the business1 and the      
gathering of the milk from many hundreds
 of farms1 and its redistribution to    
thousands of homes has made it          
impossible for the individual consumer  
to learn anything of the conditions     
surrounding production4 ,when the       
individual cannot protect himself       
against fraud and unhealthful           
conditions1 it is the duty of the       
government to protect him4 ,this is the 

theory underlying the modern control of 
food supplies1 water supplies1 and of   
living conditions in general4 ,acting on
 this basis the cities are seeking to   
control1 to an increasing degree1 the   
healthfulness and cleanliness of the    
milk supply4  ,formerly such control as 
was given was largely with reference to 
the composition of the milk1 the        
regulations providing that it should    
contain not less than a minimum amount  
of fat and other solids1 and be free    
from preservatives4 ,the more modern    
regulations are much more complex and   
touch every phase of production and     
handling that can1 in any way1 affect   
the value of the milk as human food4    
,municipal regulations4 ,the different  
cities vary widely in the methods       
employed to secure a satisfactory milk  
supply4 ,rules and regulations are      
adopted to which the producer and dealer
 must conform4 ,in order to ascertain   
whether the regulations are being       
obeyed1 two types of examinations may be

 made3 first the inspection of the farms
 and of the plants of the dealers2      
second the examination of the milk      
itself with reference to its chemical   
composition1 bacterial content and      
temperature4  ,the city of ,new ,york is
 doing more to safeguard and to improve 
its milk supply than any other large    
city in this country4 ,a brief summary  
of its regulations and methods follow4  
,a copy of the rules is furnished to    
each dairyman and is supposed to be     
posted in the stable4   ,the ,cows4  #a4
 ,the cows must be kept clean1 and      
manure must not be permitted to collect 
upon the tail1 sides1 udder and belly of
 any milch cow4  #b4 ,the cows should be
 groomed daily1 and all collections of  
manure1 mud or other filth must not be  
allowed to remain upon their flanks1    
udders or bellies during milking4  #c4  
,the clipping of long hairs from the    
udder and flanks of the cows is of      
assistance in preventing the collection 
of filth which may drop into the milk4  

,the hair on the tails should be cut1 so
 that the brush will be well above the  
ground4  #d4 ,the udders and teats of   
the cow should be thoroughly cleaned    
before milking2 this to be done by      
thorough brushing and the use of a cloth
 and warm water4  #e4 ,to prevent the   
cows from lying down and getting dirty  
between cleaning and milking1 a throat  
latch of rope or chain should be        
fastened across the stanchions under the
 cow's neck4  #f4 ,only feed which is of
 good quality and only grain and coarse 
fodders which are free from dirt and    
mould should be used4 ,distillery waste 
or any substance in a state of          
fermentation or putrefaction must not be
 fed4  #g4 ,cows which are not in good  
flesh and condition should be           
immediately removed and their milk kept 
separate until their health has been    
passed upon by a veterinarian4  #h4 ,an 
examination by a veterinary surgeon     
should be made at least once a year4    
,the ,stable4  #i4 ,no stagnant water1  

hog-pen1 privy or uncovered cesspool or 
manure pit should be maintained within  
#ajj feet of the cow stable4  #aj4 ,the 
cow stable should be provided with some 
adequate means of ventilation1 either by
 the construction of sufficient air     
chutes extending from the room in which 
the cows are kept to the outside air1 or
 by the installation of muslin stretched
 over the window openings4  #aa4        
,windows should be installed in the cow 
barn to provide sufficient light 7#b sq4
 feet of window light to each #fjj cubic
 feet of air space the minimum7 and the 
window panes be washed and kept clean4  
#ab4 ,there should be at least #fjj     
cubic feet of air space for each cow4   
#ac4 ,milch ,cows should be kept in a   
place which is used for no other        
purpose4  #ad4 ,stable floors should be 
made water-tight1 be properly graded and
 well drained1 and be of some           
non-absorbent material4 ,cement or brick
 floors are the best1 as they can be    
more easily kept clean than those of    

wood or earth4  #ae4 ,the feeding       
troughs and platforms should be well    
lighted and kept clean at all times4    
#af4 ,the ceiling should be thoroughly  
swept down and kept free from hanging   
straw1 dirt and cobwebs4  #ag4 ,the     
ceiling must be so constructed that dust
 and dirt therefrom shall not readily   
fall to the floor or into the milk4 ,if 
the space over the cows is used for     
storage of hay1 the ceiling should be   
made tight to prevent chaff and dust    
from falling through4  #ah4 ,the walls  
and ledges should be thoroughly swept   
down and kept free from dust1 dirt1     
manure or cobwebs1 and the floors and   
premises be kept free from dirt1 rubbish
 and decaying animal or vegetable matter
 at all times4  #ai4 ,the cow beds      
should be so graded and kept that they  
will be clean and sanitary at all times4
  #bj4 ,stables should be whitewashed at
 least twice a year unless the walls are
 painted or are of smooth cement4  #ba4 
,manure must be removed from the stalls 

and gutters at least twice daily4 ,this 
must not be done during milking1 nor    
within one hour prior thereto4  #bb4    
,manure should be taken from the barn1  
preferably drawn to the field4 ,when the
 weather is such that this cannot be    
done1 it should be stored not nearer    
than #bjj ft4 from the stable and the   
manure pile should be so located that   
the cows cannot get at it4  #bc4 ,the   
liquid matter should be absorbed and    
removed daily and at no time be allowed 
to overflow or saturate the ground under
 or around the cow barn4  #bd4 ,manure  
gutters should be from six to eight     
inches deep1 and constructed of         
concrete1 stone or some non-absorbent   
material4  #be4 ,the use of land plaster
 or lime is recommended upon the floors 
and gutters4  #bf4 ,only bedding which  
is clean1 dry and absorbent should be   
used1 preferably sawdust1 shavings1     
dried leaves or straw4 ,no horse manure 
should be used as bedding4  #bg4 ,the   
flooring where the cows stand should be 

so constructed that all manure may drop 
into the gutter and not upon the floor  
itself4  #bh4 ,the floor should be swept
 daily4 ,this must not be done within   
one hour prior to milking time4  #bi4   
,if individual drinking basins are used 
for the cows1 they should be frequently 
drained and cleaned4  #cj4 ,all live    
stock other than cows should be excluded
 from the room in which the milch cows  
are kept4 7,calf or bull pens may be    
allowed in the same room if kept in the 
same clean and sanitary manner as the   
cow beds47  #ca4 ,the barnyard should be
 well drained and dry1 and should be as 
much sheltered as possible from the wind
 and cold4 ,manure should not be allowed
 to collect therein4  #cb4 ,a suitable  
place in some separate building should  
be provided for the use of the cows when
 sick1 and separate quarters must be    
provided for the cows when calving4     
#cc4 ,there should be no direct opening 
from any silo or grain pit into the room
 in which the milch cows are kept4      

,the ,milk ,house4  #cd4 ,a milk house  
must be provided which is separated from
 the stable and dwelling4 ,it should be 
located on elevated ground1 with no     
hog-pen1 privy or manure pile within    
#ajj feet4  #ce4 ,it must be kept clean 
and not used for any purpose except the 
handling of milk4  #cf4 ,the milk house 
should be provided with sufficient light
 and ventilation1 with floors properly  
graded and made water-tight4  #cg4 ,it  
should be provided with adjustable      
sashes to furnish sufficient light and  
some proper method of ventilation should
 be installed4  #ch4 ,the milk house    
should be provided with an ample supply 
of clean water for cooling the milk1 and
 if it is not a running supply1 the     
water should be changed twice daily4    
,also a supply of clean ice should be   
provided to be used for cooling the milk
 to #ej degrees within two hours after  
milking4  #ci4 ,suitable means should be
 provided within the milk house1 to     
expose the milk pails1 cans and utensils

 to the sun or to live steam4  #dj4     
,facilities consisting of wash basins1  
soap and towel should be provided for   
the use of milkers before and during    
milking4 ,during the ,summer ,months the
 ,milk ,house should be properly        
screened to exclude flies4   ,the       
,milkers and ,milking4  #da4 ,any person
 having any communicable or infectious  
disease1 or one caring for persons      
having such disease1 must not be allowed
 to handle the milk or milk utensils4   
#db4 ,the hands of the milkers must be  
thoroughly washed with soap and water1  
and carefully dried on a clean towel    
before milking4  #dc4 ,clean overalls   
and jumpers should be worn during the   
milking of the cows4 ,they should be    
used for no other purpose1 and when not 
in use should be kept in a clean place  
protected from dust4  #dd4 ,the hands   
and teats should be kept dry during     
milking4 ,the practice of moistening the
 hands with milk is to be condemned4    
#de4 ,the milking stools should be at   

all times kept clean1 and iron stools   
are recommended4  #df4 ,the first       
streams from each teat should be        
rejected1 as this fore milk contains    
more bacteria than the rest of the milk4
  #dg4 ,all milk drawn from the cows #ae
 days before1 or #e days after          
parturition should be rejected4  #dh4   
,the pails in which the milk is drawn   
should have as small an opening at the  
top as can be used in milking2 top      
opening preferably not to exceed #h     
inches in diameter4 ,this lessens the   
contamination by dust and dirt during   
milking4  #di4 ,the milking should be   
done rapidly and quietly1 and the cows  
should be treated kindly4  #ej4 ,dry    
fodder should not be fed to the cows    
during or just before milking1 as dust  
therefrom may fall into the milk4  #ea4 
,all milk utensils1 including pails1    
cans1 strainers1 and dippers1 must be   
kept thoroughly clean and must be washed
 and scalded after each using1 and all  
seams in these utensils should be       

cleaned1 scraped and soldered flush4    
,the ,milk4  #eb4 ,milk from diseased   
cows must not be shipped4  #ec4 ,the    
milk must not be in any way adulterated4
  #ed4 ,the milk as soon as drawn should
 be removed to the milk house and       
immediately strained and cooled to the  
proper temperature4  #ee4 ,all milk must
 be cooled to a temperature below #ej   
degrees ,f41 within two hours after     
being drawn1 and kept thereafter below  
that until delivered to the creamery4   
#ef4 ,the milk should be strained into  
cans which are standing in ice water    
which reaches the neck of the can4 ,the 
more rapidly the milk is cooled1 the    
safer it is1 and longer it will keep    
sweet4 ,ice should be used in cooling   
milk1 as very few springs are cold      
enough for the purpose4  #eg4 ,if       
aerators are used1 they should stand    
where the air is free from dust or      
odors1 and on no account should they be 
used in the stable or out of doors4     
#eh4 ,milk strainers should be kept     

clean2 scalded a second time just before
 using1 and if cloth strainers are used1
 several of them should be provided1 in 
order that they may be frequently       
changed during the straining of the     
milk4  #ei4 ,the use of any preservative
 or coloring matter is adulteration1 and
 its use by a producer or shipper will  
be a sufficient cause for the exclusion 
of his product from the ,city of ,new   
,york4   ,water ,supply4  #fj4 ,the     
water supply used in the dairy and for  
washing utensils should be absolutely   
free from any contamination1            
sufficiently abundant for all purposes1 
and easy to access4  #fa4 ,this supply  
should be protected against flood or    
surface drainage4  #fb4 ,the privy      
should be located not nearer than #ajj  
feet of the source of the water supply1 
or else be provided with a water-tight  
box that can be readily removed and     
cleaned1 and so constructed that at no  
time will the contents overflow or      
saturate the surrounding ground4  #fc4  

,the source of the water supply should  
be rendered safe against contamination  
by having no stable1 barnyard1 pile of  
manure or other source of contamination 
located within #bjj feet of it4  ,in    
order that the farm inspection shall be 
as effective as possible1 and to make   
the work of the several inspectors as   
uniform as may be1 the dairies are      
scored4 ,a copy of the score card       
follows4     ,,department ,,of ,,health 
,the ,city of ,new ,york    ,division of
 ,general   ,sanitary ,inspection       
,dairy ,report        ,inspection ,no4  
444  ,time444444 ,a4 ,p4 ,m4            
,date444444#aia44     #a                
,dairyman444444444444444444   ,owner    
444444444444444444444    #b ,p4 ,o4     
,address4444444444444   ,p4,o4          
,address4444444,state444    #c          
,county44444 ,state44444     ,party     
,interviewed444444444444    #d ,milk    
delivered to ,creamery at4444444444     
,formerly at444444444    #e ,operated   
by444444444444444444                    

,address44444444444444444444444    #f   
,distance of farm from ,creamery44444   
,occupied farm since44444    #g ,no4    
,cows4444444 ,no4 ,milking444444 ,no4   
,qts4 ,produced444444444    #h ,all     
persons in the households of those      
engaged in producing        or handling 
milk are444444444444free from all       
infectious        disease4 ,weekly      
reports are444444444444444444being filed
                                        
4444444444444444444444444444444444444444
444444444444444444    #i ,date and      
nature of last case on                  
farm444444444444444444444444   #aj      
,,water ,,supply for utensils is from   
a444444444444444 located                
4444444444 feet deep and apparently     
is444444444444 pure and                 
wholesome444444444444  ,state any       
possible contamination       located    
within #bjj feet of source of water     
supply or       if water supply is not  
protected against surface drainage      
4444444444444444444444444444444444444444

4444444444444444444                     
4444444444444444444444444444444444444444
4444444444444444444   #aa ,water supply 
on this farm analyzed4444 #aia44        
,result44444444   #ab ,style of ,cow    
,barn4444 ,length4444 ft4   ,width4444  
ft4  ,height        of ceiling4444 ft4  
#ac ,dairy ,rules of the ,department of 
,health are44444444 posted              
444444444444444444   #ad ,dairy ,herd   
examined by4444444444444                
on44444444444444 #aia44                 
,report444444444444                     
,perfect ,allow                         
----------------------------------------
-------------------------               
,,equipment                             
#ae ,,cow ,,stable is4444444located on  
elevated                          ground
 with no stagnant water1 hog-pen1       
privy1 uncovered cesspool or manure pit 
within #ajj feet                        
#a    44444                             
#af ,,floors1 other than cow beds1 are  
of concrete or some non-absorbent       

material      #b    44444               
#ag ,floors are444properly graded and   
water-tight     #b    44444             
#ah ,cow beds are444of concrete or      
planks                             laid 
on concrete                             
#b    44444                             
#ai ,,drops are44444constructed of      
concrete1                               
stone or some non-absorbent material    
#b    44444                             
#bj ,drops are444444water-tight and     
space beneath                       is  
clean and dry4                          
#b    44444                             
#ba ,,ceiling is constructed            
of4444444and is                         
tight and dust proof                    
#b    44444                             
#bb ,,windows ,no4444444total square    
feet                               there
 is44444444444#b square feet of window  
light for each #fjj cu4 ft4 air space   
7#a                           sq4 ft4   
per each #fjj cu4 ft4--#a7              

#b    44444                             
#bc ,,ventilation consists of 444444sq4 
ft4 muslin                     in       
ceiling or4444444444which is sufficient 
#c1 fair #b1 poor #a1 insufficient #j   
#c    44444                             
#bd ,,air ,,space is444444cu4 ft4 per   
cow 7#fjj and                           
over--#c7  7#ejj to #fjj--b7  7#djj to  
#ejj--a7                        7under  
#djj--j7                                
#c    44444                             
#be ,,live ,,stock1 other than cows1    
are4444excluded                     from
 rooms in which milch cows              
are kept                                
#b    44444                             
#bf ,there is4444444444direct opening   
from stable                       into  
silo or grain pit                       
#a    44444                             
#bg ,separate quarters                  
are44444444444provided for              
cows when calving or sick               
#a    44444                             

#bh ,,cow ,,yard                        
is44444444444444properly graded and     
drained                                 
#b    44444                             
#bi ,,water ,,supply for cows           
is4444444444unpolluted                  
and plentiful                           
#a    44444                             
#cj ,,milk ,,house has44444444444direct 
opening into                     cow    
barn or other building                  
#a    44444                             
#ca ,milk house has4444444444sufficient 
light and                               
ventilation                             
#a    44444                             
#cb ,floor is44444444444444444properly  
graded and                              
water-tight                             
#a    44444                             
#cc ,milk house is44444444444properly   
screened to                             
exclude flies                           
#a    44444                             
#cd ,milk pails are444444444444of       

smoothly tinned                         
metal in good repair                    
#a    44444                             
#ce ,,milk ,,pails have44444444444all   
seams soldered                     flush
                                        
#b    44444                             
#cf ,milk pails are4444444444of the     
small mouthed                           
design1 top opening not exceeding #h    
inches                        in        
diameter4 ,diameter                     
#b    44444                             
#cg ,racks are44444444provided to hold  
milk pails                     and cans 
when not in use                         
#b    44444                             
#ch ,special milking suits              
are444444provided        #a    44444    
--------------                          
#dj                                     
,,methods                               
#ci ,,stable ,,interior painted or      
whitewashed                             
on4444444which is satisfactory #c1 fair 

#b1                                     
unsatisfactory #a1 never #j             
#c    44444                             
#dj ,,feeding ,,troughs1 platforms or   
cribs are                               
444444well lighted and clean            
#a    44444                             
#da ,celling is4444444444free from      
hanging straw1                     dirt 
or cobwebs                              
#c    44444                             
#db ,window panes are4444444444444washed
 and kept                     clean     
#a    44444                             
#dc ,,walls ,,and ,,ledges              
are444444444444444free from             
dirt1 dust1 manure or cobwebs           
#b    44444                             
#dd ,,floors ,,and ,,premises           
are4444444free from                     
from dirt1 rubbish or decayed animal or 
vegetable matter                        
#b    44444                             
#de ,,cow ,,beds are444444444clean1 dry 
and no horse                     manure 

used thereon                            
#b    44444                             
#df ,manure is4444444removed to field   
daily #d1                        to at  
least #ajj feet from barn #b1 stored    
less than #ajj feet or where cows can   
get                          at it #j   
#d    44444                             
#dg ,liquid ,matter is4444444 allowed to
 saturate                      ground   
under or around cow barn                
#b    44444                             
#dh ,milking stools are4444444clean     
#a    44444                             
#di ,cow ,yard is4444444clean and free  
from                            manure  
#b    44444                             
#ej ,,cows have444444been tuberculin    
tested and                        all   
tuberculous cows removed                
#g    44444                             
#ea ,cows are44444all in good flesh and 
condition                       at time 
of inspection                           
#b    44444                             

#eb ,cows are44444all free from clinging
                                manure  
and dirt4 7,no4 dirty444447             
#d    44444                             
#ec ,,long ,,hairs are44444kept short on
 belly1                          flanks1
 udder and tail                         
#a    44444                             
#ed ,,udder ,,and ,,teats of cows       
are444444                               
thoroughly brushed and wiped with a     
clean damp cloth before milking         
#c    44444                             
#ee ,,all ,,feed is44444of good quality 
and                                     
distillery waste or any substance in a  
state                      of           
putrefaction is444444fed                
#b    44444                             
#ef ,,milking is44444done with dry hands
             #b    44444                
#eg ,,fore ,,milk or first few streams  
from each                         teat  
is44444discarded                        
#b    44444                             

#eh ,clothing of milkers is44444clean   
#a    44444                             
#ei ,facilities for washing hands of    
milkers are                             
444444provided in cow barn or milk      
house                                   
#b    44444                             
#fj ,milk is strained at44444and44444in 
clean atmosphere                        
#a    44444                             
#fa ,milk is44444cooled within two hours
 after                          milking 
to #ej degrees ,f4 #c1 to #ee degrees   
,f4 #b to #fj degrees ,f4 #a            
#c    44444                             
#fb ,ice is44444used for cooling milk   
#a    44444                             
#fc ,,milk ,,house is44444free from     
dirt1 rubbish                        and
 all material not used in the           
handling and storage of milk            
#a    44444                             
#fd ,milk utensils are44444rinsed with  
cold                           water    
immediately after using and washed      

clean with hot water and washing        
solution       #b    44444              
#fe ,utensils are44444sterilized by     
steam or                                
boiling water after each using          
#b    44444                             
#ff ,privy is44444in sanitary condition1
 with                         vault and 
seats44444covered and protected       #a
    44444                               
--------------                          
#fj            ,remarks    ,equipment   
#dj per cent4 ,score          4444 per  
cent   ,methods #fj per cent4 ,score    
4444 per cent   ,perfect ,dairy #ajj per
 cent4 ,score     4444 per cent   ,a    
copy of the completed report is left    
with the dairyman4  ,before the farm    
inspection is carried out the creameries
 to which the milk is delivered by the  
farmers are inspected at the time the   
milk is being delivered4 ,the           
temperature of the milk and its         
cleanliness are noted4 ,in the creamery 
the straining1 cooling and handling of  

the milk are observed as well as the    
washing of the milk cans and other      
utensils1 and the construction and      
condition of the creamery1 the          
opportunity for the water supply to     
become contaminated1 and the presence of
 infectious diseases among the          
employees4  ,grades of milk4 ,three     
grades of milk have been established4   
,each dealer is required to state which 
grade or grades he expects to handle4   
,the specifications for the different   
grades are as follows4  ,grade ,a4      
,guaranteed ,milk4 ,guaranteed milk is  
that produced at farms holding permits  
therefor from the ,department of ,health
 and produced and handled in accordance 
with the following minimum requirements1
 rules and regulations3  #a4 ,only such 
cows shall be admitted to the herd as   
have not re-acted to a diagnostic       
injection of tuberculin4  #b4 ,all cows 
shall be annually tested with           
tuberculin1 and all re-acting animals   
shall be excluded from the herd4  #c4   

,no milk from re-acting animals shall be
 shipped to the ,city of ,new ,york for 
any purpose whatever4  #d4 ,the milk    
shall not contain more than #cj1jjj     
bacteria per c4 c4 when delivered to the
 consumer1 or at any time prior to such 
delivery4  #e4 ,the milk shall be       
delivered to the consumer only in sealed
 bottles1 which have been sealed at the 
dairy4  #f4 ,the milk shall be delivered
 to the consumer within #cj hours of the
 time at which it was drawn4  ,grade ,a4
 ,certified ,milk4 ,certified milk is   
milk certified by a milk commission     
appointed by the ,medical ,society of   
the ,county of ,new ,york1 or the       
,medical ,society of the ,county of     
,kings1 as being produced under the     
supervision and in conformity with the  
requirements of that commission as laid 
down for certified milk1 and sold under 
a permit therefor issued by the ,board  
of ,health4  ,no milk shall be held1    
kept1 offered for sale1 or sold and     
delivered as certified milk in the ,city

 of ,new ,york which is produced under  
requirements less than those for        
guaranteed milk4  ,grade ,a4 ,inspected 
,milk--,raw4 ,inspected milk 7raw7 is   
milk produced at farms holding permits  
therefor from the ,board of ,health1 and
 produced and handled in accordance with
 the following minimum requirements1    
rules and regulations3  #a4 ,only such  
cows shall be admitted to the herd as   
have not re-acted to a diagnostic       
injection of tuberculin4  #b4 ,all cows 
shall be tested annually with           
tuberculin1 and all re-acting animals   
shall be excluded from the herd4  #c4   
,no milk from re-acting animals shall be
 shipped to the ,city of ,new ,york for 
any purpose whatsoever4  #d4 ,the farms 
at which the milk is produced must      
obtain at least #ge points in an        
official score of the ,department of    
,health4 ,these #ge points shall be made
 up as follows3 ,a minimum of #be points
 for equipment1 and #ej points for      
method4  #e4 ,the milk shall not contain

 more than an average of #fj1jjj        
bacteria per c4 c4 when delivered to the
 consumer1 or at any time prior thereto4
  #f4 ,unless otherwise specified in the
 permit1 the milk shall be delivered to 
the consumer only in bottles4  ,grade   
,a4 ,selected ,milk--,pasteurized4      
,selected milk 7pasteurized7 is milk    
produced at farms holding permits       
therefor from the ,board of ,health1 and
 produced and handled in accordance with
 the following requirements1 rules and  
regulations3  #a4 ,the farms at which   
the milk is produced must obtain at     
least #fj points in an official score of
 the ,department of ,health4 ,of these  
#fj points1 a minimum of #bj points     
shall be required for equipment and a   
minimum of #dj points for method4  #b4  
,all milk of this grade shall be        
pasteurized1 and said pasteurization    
shall be carried on under a special     
permit issued therefor by the ,board of 
,health1 in addition to the permit for  
,selected ,milk 7,pasteurized47  #c4    

,the milk shall not contain more than an
 average of #ej1jjj bacteria per c4 c4  
when delivered to the consumer1 or at   
any time after pasteurization and prior 
to such delivery4  #d4 ,unless otherwise
 specified in the permit1 the milk shall
 be delivered to the consumer only in   
bottles4  #e4 ,all containers in which  
pasteurized milk is delivered to the    
consumer shall be plainly labeled       
,pasteurized4 ,labels must also bear the
 date and hour when pasteurization was  
completed1 the place where              
pasteurization was performed1 and the   
name of the person1 firm or corporation 
performing the pasteurization4  #f4 ,the
 milk must be delivered to the consumers
 within #cj hours after the completion  
of the process of pasteurization4  #g4  
,no milk shall be pasteurized more than 
once4  #h4 ,no milk containing in excess
 of #bjj1jjj bacteria per c4 c4 shall be
 pasteurized4  ,general ,regulations for
 ,grade ,a--  #a4 ,the caps of all      
bottles containing milk of ,grade ,a    

shall be white1 and shall contain the   
words ,grade ,a in black letters1 in    
large type4  #b4 ,if cans are used for  
the delivery of milk for ,grade ,a1 the 
said cans shall have affixed to them    
white tags1 with the words ,grade ,a    
printed thereon in black letters1 in    
large type1 together with the           
designation ,inspected ,milk 7,raw7 or  
,selected ,milk 7,pasteurized71 as the  
quality of the contents may require4    
,grade ,b4 ,selected ,milk--,raw4       
,selected milk 7raw7 is milk produced at
 farms holding permits therefor from the
 ,board of ,health1 and produced and    
handled in accordance with the following
 minimum requirements1 rules and        
regulations3  #a4 ,only such cows shall 
be admitted to the herd as have been    
physically examined by a regularly      
qualified veterinarian and declared by  
him to be healthy1 and free from        
tuberculosis in so far as a physical    
examination may determine that fact4    
#b4 ,the farms at which the milk is     

produced must obtain at least #fh points
 in an official score of the ,department
 of ,health4 ,these #fh points shall be 
made up as follows3 ,a minimum of #be   
points for equipment1 and a minimum of  
#dc points for method4  #c4 ,the milk   
shall not contain an excessive number of
 bacteria when delivered to the         
consumer1 or at any time prior thereto4 
,grade ,b4 ,pasteurized ,milk4          
,pasteurized milk 7,grade ,b7 is milk   
produced under a permit issued therefor 
by the ,board of ,health1 and produced  
and handled in accordance with the      
following minimum requirements1 rules   
and regulations and in further          
accordance with the special rules and   
regulations relating to the             
pasteurization of milk4  #a4 ,the milk  
after pasteurization must be at once    
cooled and placed in sterilized         
containers1 and the containers          
immediately closed4  #b4 ,all containers
 in which pasteurized milk is delivered 
to the consumer shall be plainly labeled

 ,pasteurized4 ,labels must also bear   
the date and hour when the              
pasteurization was completed1 the place 
where pasteurization was performed1 and 
the name of the person1 firm or         
corporation performing the              
pasteurization4  #c4 ,the milk must be  
delivered to the consumer within #cf    
hours after the completion of the       
process of pasteurization4  #d4 ,no milk
 shall be pasteurized more than once4   
#e4 ,no milk containing an excessive    
number of bacteria shall be pasteurized4
  ,general ,regulations for ,grade ,b-- 
#a4 ,caps of bottles containing milk of 
grade ,b shall be white and marked      
,grade ,b in bright green letters of    
large type4  #b4 ,the necks and         
shoulders of cans containing grade ,b   
milk shall be painted bright green1 and 
a metal tag shall be attached to each   
can with the words ,grade ,b in large   
type1 and the words of the subdivision  
to which the quality of the milk in said
 can conforms4  ,grade ,c4 ,grade ,c is 

to be used for cooking and manufacturing
 purposes only4 ,it includes all raw    
milk that does not conform to the       
requirements of any of the subdivisions 
of grade ,a or grade ,b4  #a4 ,the caps 
of all bottles containing milk of grade 
,c shall be white and shall contain in  
red the words ,grade ,c in large type   
and for cooking in plainly visible type4
  #b4 ,cans containing milk of grade ,c 
shall be painted red on necks and       
shoulders and shall have in red the     
words ,grade ,c in large type and the   
words for cooking in plainly visible    
type affixed to each can4  ,all         
creameries handling milk of different   
grades will be required to demonstrate  
to the ,department of ,health that they 
are capable of keeping the grades       
separate1 and must keep records         
satisfactory to the ,department of      
,health concerning the amount of milk of
 each grade handled each day4  ,it is to
 be noted that the grades of milk are   
based on the bacterial content of the   

milk and on the opportunity for the milk
 to become contaminated with pathogenic 
organisms4 ,from the statements made in 
a previous chapter it is evident that   
the number of bacteria in any sample of 
milk is dependent upon 7#a7 the original
 amount of contamination1 7#b7 the age  
of the milk1 and 7#c7 the temperature at
 which it has been held4 ,a high        
bacterial content is indicative of poor 
milk1 while a low bacterial content can 
be obtained1 in the case of raw milk1   
only where due attention is paid to     
cleanliness and cooling4 ,this relation 
between the quality of milk and its     
bacterial content has led many cities to
 adopt numerical bacterial standards1   
even when grades of milk have not been  
established4 ,boston requires that the  
milk shall not contain more than        
#ejj1jjj bacteria per cubic centimeter4 
,rochester1 ,n4 ,y41 has a standard of  
#ajj1jjj per cubic centimeter1 while    
,chicago requires that the milk on      
arrival in the city shall not contain   

more than #a1jjj1jjj per cubic          
centimeter from ,may first to ,september
 thirtieth1 and not over #ejj1jjj       
between ,october first and ,april       
thirtieth4 ,the sale of milk containing 
more than #c1jjj1jjj bacteria per cubic 
centimeter is prohibited4  ,it has been 
urged that bacterial standards are not  
of value since the healthfulness of milk
 depends on the kind of bacteria present
 rather than on the number4 ,it is well 
recognized that milk containing millions
 of acid-forming organisms1 butter milk1
 is a healthful food1 while that        
containing many less bacteria may       
contain some disease-producing          
organisms4 ,it has been urged that a    
qualitative standard should supplant the
 quantitative4 ,the consumer desires    
milk that has been produced under clean 
conditions1 and which has good keeping  
qualities4 ,the harmless forms of       
bacteria exert the greatest influence on
 the keeping quality4 ,experience has   
shown that the quantitative examination 

of the milk supply as it comes from the 
farm is the most feasible method of     
determining1 in the laboratory1 whether 
the farmer has obeyed the rules with    
reference to cleanliness and cooling of 
the milk4 ,the bacteriological          
examination also gives an indication as 
to whether the large number of bacteria 
is due to gross contamination of the    
milk with mud and manure1 or actual     
growth of bacteria as in old milk4 ,in  
the latter case the ordinary            
acid-forming bacteria will usually      
predominate in the milk1 while in the   
former1 the number of kinds of bacteria 
and the proportion between the kinds    
will be changed4 ,it is of course       
evident that the quantitative standards 
should be applied with judgment4  ,it is
 also claimed that the delay in securing
 the results in the quantitative        
examination of milk is an objection to  
the bacterial standard1 since the milk  
is consumed before the laboratory       
findings can be obtained4 ,it is true   

that it does not protect the community  
as far as the particular sample is      
concerned1 but it is also true that the 
examination is not made for the purpose 
of determining the condition of the     
particular sample1 so much as it is to  
determine the methods that are employed 
on any particular farm1 and these do not
 vary widely from day to day4 ,thus1 if 
a number of samples give high results1  
it is evident that conditions           
surrounding production need             
investigation4  ,if the milk is well    
cooled on the farm1 and kept cold while 
being shipped1 the growth of bacteria   
will be slow1 and the condition of the  
milk as far as keeping quality is       
concerned1 much better than if less care
 is used4 ,some cities have temperature 
standards2 ,new ,york requires that the 
milk shall be cooled to #ej ,f4 on the  
farm1 and shall not be above #ej ,f4 on 
arrival in the city4 ,others require    
that it shall not be above #ej ,f4 on   
delivery to the consumer4  ,certified   

milk4 ,in many cities the ,medical      
,societies have appointed ,milk         
,commissions1 that adopt rules and      
regulations1 concerning the production  
of milk that shall receive the          
certificate of the commission4          
,producers1 who desire to have their    
milk thus certified1 must satisfy the   
commission that they are able to conform
 to the rules4 ,the commission appoints 
a physician to examine the personnel of 
the farm1 a veterinarian to make        
frequent examinations of the herd1 a    
chemist to examine the milk as to its   
contents in fat and other solids1 and a 
bacteriologist to determine the         
bacterial content of the milk4 ,the     
rules are very stringent and cover every
 point that may influence1 in any way1  
the value of the milk as human food4 ,in
 order to conform to these requirements1
 a heavy expenditure must be incurred1  
and the business must pay for such      
expert service2 hence1 certified milk   
must be sold at high prices1 twelve to  

twenty-five cents per quart4 ,this price
 makes it a special product and its use 
is confined mainly to infant feeding4   
,the bacterial standard for certified   
milk is usually #aj1jjj bacteria per    
cubic centimeter4 ,it is only by the    
exercise of the greatest care at every  
point that the bacterial content can be 
kept below this maximum4  ,the term     
certified milk has been registered by   
,mr4 ,francisco of ,new ,jersey1 who was
 the first to engage in the production  
of such milk under the direction of the 
,medical ,milk ,commission of ,essex    
,county1 ,new ,jersey4 ,the use of the  
term is allowed when the milk is        
produced under the regulation of any    
,medical ,milk ,commission4  ,most      
certified milk is now produced on fancy 
dairy farms conducted by wealthy men4   
,the barns and other equipment are the  
best that can be obtained1 and the      
methods employed1 as far as cleanliness 
is concerned1 are extreme4 ,in some of  
the dairies the bacterial content is    

reduced to a few hundred per cubic      
centimeter1 or to that which is derived 
from the interior of the udder4 ,such   
milk will1 when well refrigerated1 keep 
for long periods of time4 ,it is a not  
uncommon thing for such milk to keep    
perfectly sweet for ten to fifteen days4
  ,tests for the quality of milk4 ,at   
the milk depot and elsewhere1 it is     
frequently desired to determine the     
bacterial condition of the milk in a    
less refined manner than by the plate   
cultures of the bacteriologist1 which   
require a large amount of time for their
 preparation and do not yield any       
positive information for at least       
twenty-four hours4 ,there are a number  
of such tests that may be applied4      
,illustration3 ,fig4 #ci4--,sediment    
,testers4  ,in the use of the apparatus 
on the right1 increased air pressure is 
used to hasten the filtering process2   
the same is accomplished in the         
apparatus shown in the center by warming
 the milk by the injection of steam     

between the walls of the double jacket4 
#a4 ,dirt or sediment test4 ,this is    
made by filtering a pint of the mixed   
milk through a small disc of absorbent  
cotton4 ,the insoluble dirt is retained 
and imparts a color to the cotton1 the  
shade of which is dependent on the      
amount of dirt 7,p4 #de74 ,since it is  
impossible to have dirt without         
bacteria1 it is evident that milks      
containing a large amount of dirt will  
be high in bacteria4 ,the reverse1      
however1 is not necessarily true4       
,illustration3 ,fig4 #dj4--;,good ,milk4
  ,a plate culture inoculated with      
#a_/ajj of a cubic centimeter of milk   
containing #fg colonies1 which equals   
#f1gjj bacteria per cubic centimeter of 
milk4 ,such milk will keep well4  #b4   
,acidity test4 ,the acidity of the milk 
is also an indication of its bacterial  
content4 ,if the acidity has increased1 
above the normal for fresh milk1 the    
bacterial content is certain to be high1
 and the keeping quality poor4 ,an      

acidity above #j4b per cent in market   
milk is to be avoided1 as an increase in
 acidity is always preceded by a great  
increase of bacteria4  ,whether the     
acidity is above or below this point can
 be rapidly and easily determined at the
 receiving station by a modification of 
the ,farrington acid test4 ,dissolve one
 alkaline tablet in an ounce of water4  
,a unit volume of this solution added to
 a unit volume of milk is equal to #j4a 
per cent of acidity4 ,if two measures   
are provided1--one for the alkaline     
solution holding just twice as much as  
that used for the milk1 the approximate 
acidity can be quickly determined by    
mixing a measure of each in a common    
white cup4 ,if the acidity is above #j4b
 per cent the color will remain white2  
if a pink color develops1 it indicates  
an acidity less than this amount4 ,this 
test is also useful in the selection of 
milk or cream that is to be used for    
special purposes1 such as               
pasteurization4  ,illustration3 ,fig4   

#da4--,poor ,milk4  ,a plate culture    
inoculated with #a_/ajjj of a cubic     
centimeter of market milk containing    
#a1fhj colonies1 which equals #a1fhj1jjj
 bacteria per cubic centimeter4 ,such   
milk has poor keeping qualities4  #c4   
,alcohol test4 ,a test giving similar   
information is made by adding two parts 
of #gj per cent alcohol to one part of  
milk1 and noting whether curdling       
occurs4  #d4 ,curd test4 ,the curd test 
described on p4 #ajj gives no indication
 of the number of bacteria present1 only
 concerning the types present4 ,it has  
been proposed to combine the            
fermentation test with the reduction    
test referred to below and thus gain    
some idea of1 not only the number1 but  
the kinds of bacteria present4  #e4     
,reduction test4 ,the reduction test is 
made by adding to twenty cubic          
centimeters of milk1 one-half cubic     
centimeter of a solution of methylene   
blue1 a coal tar dye4 ,a saturated      
solution of the dye is made in alcohol1 

and #b4e per cent of this solution added
 to water4 ,the time required for the   
reduction of the dye or the change of   
the color from blue to white when the   
samples are placed in tubes and kept at 
#ih to #ajj ,f41 is dependent upon the  
number of bacteria present4 ,by allowing
 the tubes to stand until curdling      
occurs1 and noting the nature of the    
curd1 whether the solid curd of the     
desirable acid-forming bacteria or the  
gassy curd of the harmful types is      
produced1 knowledge is gained of the    
kinds of bacteria present4  ,according  
to ,barthel1 milks that reduce the      
methylene blue within fifteen minutes   
contain hundreds of thousands of        
bacteria per cubic centimeter4 ,those   
that require from fifteen minutes to one
 hour for the disappearance of the color
 are also high in bacteria1 and are to  
be classed as a poor grade of market    
milk4 ,if one to three hours is         
required1 the milk is comparatively low 
in bacteria1 and is to be classed as a  

good grade of market milk4 ,when more   
than three hours elapse before the      
disappearance of the blue color1 the    
bacterial content is low and the milk is
 to be placed in the highest grade4     
,the time of reduction is only a rough  
index of the number of bacteria present1
 but it gives a good idea of the keeping
 quality of the milk1 and of the        
conditions of production and handling4  
,of the above tests the sediment and    
acid tests are more frequently used4    
,examination of milk sediments4 ,in the 
modern municipal laboratory1 efforts are
 made to determine1 as far as possible1 
the conditions of production on the     
farms1 by an examination of the milk in 
the laboratory4 ,the samples of milk are
 sedimented in a small centrifuge1 and  
an examination of the sediment made with
 the microscope4 ,the types of bacteria 
and the number of body cells found is an
 indication as to whether any of the    
animals of the herd are suffering from  
inflammation of the udder4 ,the test    

also gives information similar to the   
dirt test since the insoluble dirt will 
be thrown down and will impart a color  
to the sediment4  ,pasteurization of    
market milk44,the spread of the         
pasteurizing process as applied to      
market milk has been rapid4 ,this has   
been due to the recognition of the fact 
that only by this process can a safe    
milk i4e41 one free from pathogenic     
bacteria1 be obtained4 ,as previously   
mentioned a small proportion of all     
human beings that have suffered from    
typhoid fever become bacillus carriers4 
,it is impossible to examine all persons
 who may be concerned in the handling of
 milk in order to ascertain whether they
 belong to this dangerous and           
unfortunate class of people4  ,the      
larger cities have also recognized the  
impossibility of requiring the          
tuberculin test of all cattle furnishing
 milk4 ,pasteurization remains the only 
safeguard1 and it is probable that      
within a short time all the larger      

cities will require the pasteurization  
of all milk1 except that produced under 
strict supervision4  ,as previously     
mentioned heating causes certain changes
 in milk4 ,in the treatment of market   
milk it is desirable to use as low      
temperatures as will suffice to destroy 
the disease-producing bacteria4 ,it is  
fortunate that temperatures that will   
insure this result have little effect on
 the milk4 ,the temperatures now        
recommended for pasteurization are as   
follows3    #aeh degrees ,f4 for #c     
minutes4   #aee degrees ,f4 for #e      
minutes4   #aeb degrees ,f4 for #aj     
minutes4   #adh degrees ,f4 for #ae     
minutes4   #ade degrees ,f4 for #ah     
minutes4   #adj degrees ,f4 for #bj     
minutes4  ,in actual practice the milk  
is heated to #ade degrees for #be to #cj
 minutes4 ,the acid-forming bacteria are
 not completely destroyed and the       
pasteurized milk as a rule will undergo 
the same type of fermentation as raw    
milk4 ,it is1 however1 deemed essential 

that all pasteurized milk be sold as    
such2 that it be delivered to the       
consumer within twenty-four hours after 
pasteurization and that no milk be      
pasteurized a second time4  ,the        
continuous pasteurizing machines have   
the disadvantage that a small portion of
 the milk passes through so quickly that
 all pathogenic bacteria therein might  
not be destroyed1 7p4 #aca74 ,this has  
led to the use of the holding process in
 which the milk is heated to the desired
 temperature and then placed in tanks   
where it remains at this temperature for
 any desired time4 ,every portion is    
thus treated in a uniform manner4  ,if  
the milk is bottled after               
pasteurization1 there remains           
opportunity for reinfection1 possibly   
with typhoid bacilli4 ,pasteurization in
 the final container1 the bottle1 is    
being recommended4 ,this is possible    
only when a special bottle is used with 
a metal cap lined with paper4  ,milk    
distribution4 ,until within recent years

 in the cities and at present in smaller
 towns1 milk is largely retailed from   
cans which are carried on the wagons or 
are kept in stores4 ,this exposes the   
milk to contamination from street dust  
and from the container furnished by the 
consumer4 ,it is well recognized that   
every utensil with which milk is brought
 in contact adds more or less bacteria  
to it1 and the less milk is handled1 the
 better will be its condition when it   
reaches the consumer4 ,milk is now      
largely retailed in glass bottles which 
are closed with pulp caps4 ,in some     
cities the bottling is mainly done in   
the country at the bottling station to  
which the milk is brought by the        
farmers2 or it may be shipped by the    
producer to a distributing company1 and 
all subsequent treatment1 as            
pasteurization and bottling done in the 
city4  ,milk plants are now generally   
equipped for the rapid and economical   
handling of large quantities of milk in 
a most sanitary manner4 ,the bottles as 

they are returned from the consumer are 
washed in a continuously-acting         
automatic washer which washes1 rinses   
and sterilizes the bottles without their
 being removed from the cases in which  
they are carried on the wagons4 ,these  
machines are effective1 if not run at   
too rapid a rate1 so that the bottles   
are not exposed for a sufficiently long 
period of time to sterilize them4 ,the  
bottles are then filled and the paper   
caps inserted by machinery4 ,the caps   
can now be obtained from the            
manufacturers in sealed tubes in which  
they have been sterilized so that the   
contamination from this source is       
avoided4 ,the shipping cans are washed  
and sterilized with live steam1 and in  
many plants are thoroughly dried1 by    
passing hot air into them4 ,under these 
conditions they then reach the farmer   
with none of the musty and disagreeable 
odor that frequently is present when the
 can contains a small quantity of water1
 condensed from steam4  ,the top of the 

milk bottle over which the milk is      
poured is exposed to contamination from 
the hands of the deliveryman4 ,trouble  
from this source can be avoided if the  
consumer cleans the lip of the bottle   
before removing the cap4 ,the better    
grades of milk are dispensed in bottles1
 the top of which is protected by an    
additional cover of paper or tin foil   
which reaches to the neck of the bottle 
and is held in place by a crimped metal 
band4  ,milk supply of the small cities4
 ,it is true that the quality of milk   
supplied to the large cities by the     
great milk companies is generally much  
superior to that sold in the smaller    
cities and villages4 ,many of the       
smaller places are however1 attempting  
in various ways to improve their supply4
 ,it is evident that methods will be    
successful here that can not be employed
 in the larger places4 ,a detailed and  
careful farm inspection by a tactful1   
capable inspector1 coupled with proper  
publicity will do much to improve       

conditions4 ,the publication of the     
scores of the different farms1 and the  
demonstration of the sediment test as   
applied to their product attracts       
favorable attention to the good dairies 
and unfavorable attention to the poor4  
,this usually has an effect on the trade
 sufficient to cause the negligent      
producer and dealer to improve4  ,it is 
also becoming recognized that high grade
 milk can be produced with very simple  
equipment4 ,in fact the small farm is   
often more successful in producing high 
grade milk than is the large farm on    
which the work must be done by hired    
help for here the personality of the    
owner can not make itself felt as where 
the producer is doing a portion of the  
work about the barn and dairy himself4  
,it is becoming more and more evident   
that the chief factor in the production 
of clean milk is the personality of the 
producer2 he should be one who gets     
enjoyment out of his clean stables and  
cows and his high grade product4  ,the  

man who is producing milk for the city  
market is but one of many and his       
individual efforts can not make         
themselves felt4 ,the dairyman who is   
marketing his own product is in a       
position where his efforts to produce a 
fine product should prove of distinct   
advantage to him in enabling him to sell
 it for a higher price than that        
obtained for ordinary milk4  ,it should 
be remembered that the production of    
clean1 healthful milk is not a question 
of equipment1 but of methods and of     
additional work4 ,the cows must be fed1 
the stables must be cleaned1 the cows   
milked1 and the milk delivered to the   
consumer4 ,if beyond this unavoidable   
labor a small additional amount is      
expended1 the improvement in the product
 will be great4 ,it is necessary that   
the additional work be placed where it  
will do the most good1 in keeping the   
cows clean both summer and winter so    
that little need be done in cleaning    
them before milking1 the pails and other

 utensils kept clean and sterilized1 and
 the milk cooled as soon as possible and
 kept cold until delivered to the       
consumer4 ,the delivery should be made  
within the shortest practicable time    
after the milk is drawn4 ,in order that 
the healthfulness of the milk may be    
beyond question1 the herd must be kept  
free from tuberculosis and some         
attention should be paid to the health  
of the men1 especially with reference to
 whether they may be typhoid carriers or
 not4 ,the necessary labor should not   
increase the cost of the milk over one  
cent per quart4 ,it has been shown in   
many cases that such a product can be   
marketed at a price that will more than 
compensate for the additional cost4     
,clean1 fresh1 rich milk is being sold  
in villages and small cities located in 
the great butter and cheese producing   
sections of the country for eight to ten
 cents per quart4  ,the duty of the     
consumer4 ,the educational campaign that
 has been carried on by the health      

departments with reference to farm      
conditions and methods of handling has  
been most effective in improving the    
milk supply4 ,many cities are now       
extending this to the consumer1         
recognizing that as much harm may be    
done in the home as on the farm4 ,the   
importance of keeping the milk cold1 of 
not allowing it to stand exposed in open
 vessels1 of thoroughly cleaning the    
vessel in which it is kept1 or the milk 
bottle before returning it to the       
milkman are especially emphasized4      
,moreover1 it must be impressed upon the
 consumer that all of these             
improvements1 not only on the farm where
 the milk is produced1 but in the hands 
of the distributing companies in the    
cities1 involve much expense1 and cannot
 be carried out1 unless the consumer is 
willing to pay their cost4 ,more        
objection seems to be raised over an    
increase in the price of milk than any  
other food stuff4 ,the consumer         
therefore needs education along the line

 of higher prices for milk4 ,dairy      
products of all types have increased    
much in value in recent years1 so that  
at present prices milk1 sold directly as
 milk1 is relatively cheaper than in any
 form1 when prevailing prices are       
compared with those that obtained a     
decade ago4     ,,index4   ,abnormal    
fermentations1 overcoming of1 #ajh4     
,abortion1 contagious1 #ge4  ,acid1     
amount of formed in milk1 #hd4  ,acidity
 test1 #baa4  ,actinomycosis1 #ge4      
,aeration of milk1 #ee4  ,aerobic       
bacteria1 #ac4  ,air1 contamination of  
milk from1 #ea4  ,alcohol test1 #bac4   
,alcoholic fermentation1 #if4           
,anaerobic bacteria1 #ac4  ,animal1     
contamination of milk from1 #db4        
,anthrax1 #ge4  ,antiseptics1 #af1 #aag4
   ,b4  ,bacillus ,bulgaricus1 #hi1     
#aja4  ,bacillus lactis acidi1 #hf4     
,bacteria1 aerobic1 #ac2   anaerobic1   
#ac2   culture media for1 #bj2          
desirable acid-forming1 #hf2            
determining number of1 #bb2             

distribution of1 #ah2   effect of cold  
on1 #ad2   effect of heat on1 #ae2      
food of1 #ab2   forms of1 #h2   manner  
of growth of1 #i2   movement of1 #aa2   
nature of1 #h2   parasitic1 #aa2        
products of1 #ag2   pure cultures of1   
#be2   rate of growth of1 #ac2          
relation to air1 #ac2   relation to     
chemicals1 #af2   relation to drying1   
#ae2   relation to light1 #af2          
relation to temperature1 #ab2   size of1
 #i2   saprophytic1 #aa2   spores of1   
#aj2   types of acid-forming1 #hf2      
undesirable acid-forming1 #ij4          
,bedding1 #dg4  ,bitter fermentation1   
#ig4  ,bleaching powder1 #aab4  ,bloody 
milk1 #ii4  ,butter1 bacteria in1 #aed2 
bacterial defects in1 #aef2   cowy odor 
in1 #aeg2   deterioration of1 #aee2     
fishy1 #aeg2   metallic1 #aeg2   molding
 of1 #aeg2   preservatives in1 #aee2    
putrid1 #aef2   source of flavor1 #adj2 
turnip flavored1 #aef2   types of1 #acg4
  ,butter-milk1 #ajj4  ,butyric         
fermentation1 #ic4  ,boric acid1 #aag4  

,borax1 #aag4   ,c4  ,carbolic acid1    
#aaa4  ,cheese1 abnormal fermentations  
of1 #agd2   bitter1 #agg2   ,camembert1 
#ahf2   ,cheddar1 #afd2   colored1 #agh2
   flavor production in1 #agb2   gassy1 
#agd2   ,gorgonzola1 #ahe2   ,limburger1
 #ahg2   moldy1 #agi2   preservation of 
by acid1 #aga2   putrid1 #agh2   quality
 of milk for1 #afb2   ripening of1 #afi2
   ,roquefort1 #ahd2   ,stilton1 #ahe2  
,swiss1 #ahj2   temperature of ripening1
 #agc2   types of1 #afa4  ,children1    
diseases of1 #hj4  ,chloride of lime1   
#aab4  ,cholera1 #hj4  ,cleaning        
utensils1 #ci4  ,clean milk1 production 
of1 #ec4  ,cold1 effect of1 on bacteria1
 #ad4  ,colored milk1 #ih4  ,condensed  
milk1 #ace4  ,contagious abortion1 #ge4 
,contamination of milk1 from milking    
machine1 #ej2   in factory1 #ei4        
,cooling of milk1 #ed4  ,corrosive      
sublimate1 #aaa4  ,cream1 control of    
fermentation of1 #adb2   pasteurization 
of1 #adf2   ripening of1 #ach2          
separators1 #cf4  ,cresol1 #aaa4  ,curd 

test1 #ajd4  ,cycle of fermentations1   
#ii4   ,d4  ,deodorants1 #aji4          
,digestive fermentation1 #ic4           
,diphtheria1 #gi4  ,dirt1 exclusion of1 
#dd2   removal of from milk1 #ec4       
,disinfectants1 #af1 #aji4              
,disinfection1 #aji4  ,distribution of  
bacteria1 #ah4  ,dried milk1 #ace4      
,drugs1 excretion of in milk1 #eh4      
,drying1 effect of on bacteria1 #ae4    
,e4  ,emmenthaler cheese1 #ahj4         
,evaporated milk1 #acd4   ,f4  ,factory 
by-products1 #cf2   treatment of1 #ch4  
,feeds1 effect of on milk1 #eg4         
,fermentation test1 #ajd4  ,fermented   
milks1 #ajj4  ,fly1 contamination of    
milk by1 #fj2   means of spreading      
typhoid fever1 #gh4  ,foot and mouth    
disease1 #gd4  ,fore milk1 #ca2         
rejection of1 #cd4  ,formalin1 #aab4    
,g4  ,galactase1 #agb4  ,garget1 #ge4   
,germicidal action of milk1 #cc4        
,gorgonzola cheese1 #ahe4   ,h4  ,hairs1
 bacteria on1 #dc4  ,heat1 effect on    
bacteria1 #ae4  ,heated milk1 detection 

of1 #ci4  ,hydrogen peroxide1 #aah4     
,k4  ,kefir1 #ajb4  ,koumiss1 #ajb4     
,l4  ,lange ,wei1 #ie4  ,light1 effect  
on bacteria1 #af4  ,limburger cheese1   
#ahg4  ,lime1 #aaj4  ,lumpy jaw1 #ge4   
,m4  ,malta fever1 #ge4  ,market milk1  
municipal regulations concerning1 #aij2 
pasteurization of1 #bad4  ,milk1 acid   
fermentation of1 #hc2   aeration of1    
#ee2   affected by feed1 #eg2           
alcoholic fermentation of1 #if2         
bacterial standards for1 #bjf2   bitter 
fermentation of1 #ic2   certified1 #bjb2
   butyric fermentation of1 #ic2        
certified1 #bjb1 #bjh2   clarifying of1 
#aae2   condition of when secreted1 #bi2
   contamination of from animal1 #db2   
from by-products1 #cf2   from utensils1 
#cd2   contamination of with tubercle   
bacilli1 #fg2   cooling of1 #ed2        
creaming of1 #acf2   culture medium for 
bacteria1 #bh2   cycle of fermentation  
in1 #ii2   distribution of1 #baf2       
digestive fermentation of1 #ic2   dirt  
in1 #dd2   effect of heat on1 #aai2     

filtration of1 #aad2   germicidal action
 of1 #cc2   grades of1 #bja2            
guaranteed1 #bja2   inspected1 #bjb2    
miscellaneous fermentations of1 #ih2    
pasteurization of1 #abj2                
pasteurization of in home1 #aca2        
preservation of by antiseptics1 #aag2   
preservation of by cold1 #aaf2          
relation to children's diseases1 #hj2   
ropy fermentation1 #id2   sediments1    
examination of1 #bad2   selected1 #bjc2 
slimy1 #id2   spontaneous fermentation  
of1 #ia2   sterilization of1 #acd2      
straining of1 #aec2   supply of small   
cities1 #bag2   sweet curdling          
fermentation of1 #ib2   tainted1 #ef1   
#eh2   temperature standards for1 #bjh2 
tests for quality of1 #bji4  ,milk      
pails1 sanitary1 #dh2   small topped1   
#dh4  ,milker1 factor in contamination  
of milk1 #ea4  ,milking-machines1 #cf1  
#ej4  ,mold on butter1 #agg2   on       
cheese1 #agi4   ,o4  ,odors1 absorption 
of1 #ef1 #eh4  ,oidium lactis1 #ahf4    
,oleomargarine1 #aeb4  ,p4              

,pasteurization1 #abj2   efficiency of1 
#acc2   purpose of1 #abc2   methods of1 
#abe4  ,pasteurized milk1 fermentations 
in1 #abd4  ,pasteurizing machines1 tests
 of1 #acj4  ,process butter1 #aeb4      
,ptomaine poisoning1 #ha4  ,pure        
cultures1 #be4   ,r4  ,rabies1 #ge4     
,reduction test1 #bac4  ,rennet1 #agj4  
,ropy fermentation1 #id4  ,roquefort    
cheese1 #ahd4  ,rusty spot in cheese1   
#agh4   ,s4  ,salicylic acid1 #aag4     
,scarlet fever1 #gi4  ,score card for   
dairies1 #aih4  ,sediment test1 #baj4   
,skim milk1 heating of1 #ch4  ,slimy    
fermentation1 #id4  ,spores of bacteria1
 #aj4  ,stalls1 #df4  ,starters1 #adc2  
for cheese1 #afg2   propagation of1     
#adf4  ,sterilization1 #ba1 #acd4       
,stilton cheese1 #ahe4  ,storch test1   
#ci4  ,straining of milk1 #cc4          
,sulphur1 #aaa4  ,sweet curdling of     
milk1 #ib4  ,swiss cheese1 #ahj4   ,t4  
,taints1 determination of cause of1 #eh1
 #ajc4  ,temperature effect on growth1  
#ab4  ,tubercle bacilli1 destruction of1

 #ga2   in butter1 #gj2   in cheese1    
#gj2   in milk1 #fg4  ,tuberculin test1 
#gc4  ,tuberculosis1 #fd2   closed1 #gj2
   distribution of disease in animal1   
#ff2   economic aspects of1 #gb2   open1
 #gj4  ,typhoid fever1 #gf4   ,u4       
,udder1 inflammation1 #ge2   invasion of
 by bacteria1 #cj2   number and kind of 
bacteria from1 #cb2   structure of1 #cj2
   washing of1 #dg2   cleaning of1 #ci4 
,utensils1 contamination from1 #cd4     
,w4  ,water1 effect on butter1 #aec2    
supply1 #ei2   testing of1 #fj4  ,whey1 
heating of1 #ch4  ,wisconsin curd test1 
#ajd4   ,y4  ,yeast fermentation1 #if4  
,yoghurt1 #aja4