,transcriber's ,notes ,obvious typographical errors have been silently corrected4 ,several tables have been divided with duplication of the first column because of their excessive width4 ,italics are represented thus italic4 ,issued ,march #ag1 #aiaa4 ,u4 ,s4 ,,department ,,of ,,agriculture1 ,,bureau ,,of ,,animal ,,industry4--,,bulletin #acb4 ,a4 ,d4 ,,melvin1 ,,chief ,,of ,,bureau4 ,a ,,bacteriological ,,study ,,of ,,ham ,,souring4 ,,by ,c4 ,n4 ,mc,b,r,y,d,e1 ,m4 ,d41 ,senior ,bacteriologist1 ,biochemic ,division4 ,illustration3 ,,united ,,states ,,department ,,of ,,agriculture4 ,,washington3 ,,government ,,printing ,,office4 #aiaa4 ,,the ,,bureau ,,of ,,animal ,,industry4 ,chief3 ,a4 ,d4 ,,melvin4 ,assistant ,chief3 ,a4 ,m4 ,,farrington4 ,chief ,clerk3 ,,charles ,c4 ,,carroll4 ,animal ,husbandry ,division3 ,,george ,m4 ,,rommel1 chief4 ,biochemic ,division3 ,m4 ,,dorset1 chief4 ,dairy ,division3 ,b4 ,h4 ,,rawl1 chief4 ,inspection ,division3 ,,rice ,p4 ,,steddom1 chief2 ,r4 ,a4 ,,ramsay1 ,,morris ,,wooden1 and ,,albert ,e4 ,,behnke1 associate chiefs4 ,pathological ,division3 ,,john ,r4 ,,mohler1 chief4 ,quarantine ,division3 ,,richard ,w4 ,,hickman1 chief4 ,zoological ,division3 ,b4 ,h4 ,,ransom1 chief4 ,experiment ,station3 ,e4 ,c4 ,,schroeder1 superintendent4 ,editor3 ,,james ,m4 ,,pickens4 ,,letter ,,of ,,transmittal4 ,,united ,,states ,,department ,,of ,,agriculture1 ,,bureau ,,of ,,animal ,,industry1 ,washington1 ,d4 ,c41 ,november #b1 #aiaj4 ,,sir3 ,i have the honor to transmit and to recommend for publication as a bulletin of this ,bureau a paper entitled 8,a ,bacteriological ,study of ,ham ,souring10 by ,dr4 ,c4 ,n4 ,mc,bryde1 senior bacteriologist in the ,biochemic ,division of this ,bureau4 ,the souring of hams is a source of considerable loss in the meat-packing industry1 and the cause of this trouble has heretofore been in doubt4 ,dr4 ,mc,bryde's paper presents the results of an exhaustive study of the subject1 from which it appears that he has succeeded in discovering the true cause of the trouble4 ,besides a description of the experimental work the paper discusses methods of preventing the souring of hams and the proper disposal of those which have become affected4 ,respectfully1 ,a4 ,d4 ,,melvin1 ,chief of ,bureau4 ,hon4 ,,james ,,wilson1 ,secretary of ,agriculture4 ,,contents4 ,page4 ,introductory #g ,method of curing hams #h ,definition of souring #aj ,classification of sour hams and location of sour areas #aj ,method of detecting sour hams #ab ,theories in regard to ham souring #ab ,previous experimental work to determine cause of ham souring #ac ,the present experiments #ad ,media employed #ad ,method of procedure in examining hams #ae ,results of examination of sour and sound hams #af ,histological changes in sour hams #ag ,chemical analyses of sour and sound hams #ah ,bacteriological examination of sour and sound hams #bj ,inoculation experiments with hams #ba ,probable method by which ham-souring bacillus enters hams #cc ,possibility of infection prior to slaughter #cc ,possible infection from pickling fluids #cd ,experiment to show whether infection takes place from the curing pickle #cd ,possible infection through manipulation or handling #ce ,infection from ham thermometers #ce ,experiment to show whether hams become infected from ham thermometers #cg ,infection from pumping needles #da ,infection from billhooks #db ,biological and morphological characteristics of the ham-souring bacillus #dc ,conditions favorable to growth #dc ,growth on different culture media #dc ,morphology #df ,spore formation #df ,resistance to heat and chemical agents #dg ,gas production #dg ,acid production #dh ,pathogenic properties #dh ,nature of the bacillus #dh ,prevention of ham souring #ej ,general summary and conclusions #ec ,acknowledgments #ee ,,illustrations4 ,,plates4 ,page4 ,,plate ,i4 ,fig4 #a4--,section of muscular tissue from sound ham1 showing muscle fibers cut longitudinally2 nuclei sharply defined and cross striation distinct4 ,fig4 #b4--,section of muscular tissue from sour ham1 showing muscle fibers cut longitudinally2 nuclei undergoing disintegration and cross striation indistinct #af ,,ii4 ,fig4 #a4--,section through muscular tissue of ham which has undergone natural or spontaneous souring1 showing distribution of bacilli between the muscle fibers1 which are cut obliquely4 ,fig4 #b4--,section through muscular tissue of ham which has undergone natural or spontaneous souring1 showing individual bacilli between the muscle fibers1 which are cut somewhat obliquely #ah ,,iii4 ,fig4 #a4--,section through muscular tissue of artificially soured ham1 showing distribution of bacilli between the muscle fibers1 which are shown in cross section4 ,fig4 #b4--,section through muscular tissue of artificially soured ham1 showing individual bacilli between the muscle fibers1 which are cut longitudinally #bf ,,iv4 ,glucose bouillon culture in ,smith fermentation tube at four days #dh ,,text ,,figures4 ,,fig4 #a4 ,cross section through body of ham1 with sour areas indicated by shading and dotted lines #aa #b4 ,cross section through body of ham to show method of sampling for chemical analysis #ah #c4 ,cross section through body of artificially soured ham1 showing sour areas and points at which cultures were taken #be #d4 ,diagrammatic views showing construction of ham thermometer #cf #e4 ,ham-souring bacillus 7,bacillus putrefaciens71 grown on egg-pork medium #df ,a ,,bacteriological ,,study ,,of ,,ham ,,souring4 ,,introductory4 ,the souring of hams is a matter of considerable importance to those engaged in the meat-packing industry1 and has been the occasion of no little worry1 as in even the best-regulated packing establishments the yearly losses it entails are considerable4 ,the subject has given rise to much speculation on the part of those engaged in the curing of meats1 as to the cause of the trouble and how it may be remedied1 and has received considerable attention in a practical way1 but little seems to have been done in a scientific way toward determining the cause and nature of ham souring4 ,in a well-regulated meat-packing establishment the loss from ham souring is usually figured at about one-tenth of #a per cent of the total weight of hams cured4 ,at first thought this would seem but a small loss1 but when one reflects that in a single large packing establishment some #c1jjj1jjj hams are cured during the year1 the loss1 when figured out1 is considerable4 ,taking #ae pounds as the average weight of a ham1 #c1jjj1jjj hams would represent #de1jjj1jjj pounds of meat4 ,figuring the loss from souring on the basis mentioned1 the amount of meat condemned and destroyed during the year would be #de1jjj pounds4 ,assuming that hams sell at an average wholesale price of #ae cents a pound1 the yearly loss for a single plant which cures #c1jjj1jjj hams a year would be nearly #g1jjj4 ,while one-tenth of #a per cent of the total weight of hams cured would represent the loss from souring in a well-regulated establishment1 statistics obtained through ,government meat inspectors show that #j4be per cent would more nearly represent the loss for the entire country4 ,during the fiscal year from ,july #a1 #aijh1 to ,june #cj1 #aiji1 some #fgj1jjj1jjj pounds of hams were placed in cure in packing establishments subject to ,government inspection4 ,estimating the loss from souring at #j4be per cent1 the total amount of meat condemned and destroyed as sour would be #a1fge1jjj pounds4 ,at #ae cents a pound the total annual loss from ham souring in packing houses subject to ,government inspection would figure up something over a quarter of a million of dollars4 ,the problem of ham souring1 therefore1 is quite an important one from a practical and financial standpoint2 but aside from these considerations it is also a subject of considerable scientific interest1 and in view of the fact that all sour meats are condemned under the ,federal regulations governing meat inspection it has seemed fitting that this question should be made the subject of scientific investigation on the part of the ,bureau which is charged with the administration of this inspection4 ,the investigation reported in this paper has been conducted chiefly along bacteriological lines1 and has been confined entirely to the wet method of curing hams1 as this method is the one generally used in ,american packing houses4 ,,method ,,of ,,curing ,,hams4 ,in order to make clear certain points in regard to the nature and occurrence of ham souring and to insure a better understanding of the experiments which are to be described later1 it would seem best to begin with a brief outline of the method of curing hams as practiced in the larger packing establishments of the country4 ,this description is merely a general outline of the method of preparing hams for cure and the method of handling hams while in cure1 and deals chiefly with those points that bear on the question of souring4 ,after the slaughtered animal has been cleaned1 scraped1 eviscerated1 washed1 and split down the middle1 the carcass is usually allowed to hang for an hour or so in a large room open to the outside air1 known as the 8hanging floor40 ,this is done with a view to getting rid of a certain amount of the body heat before the carcass is run into the chill rooms1 and effects a saving in refrigeration4 ,the carcasses are next run into 8coolers0 or chill rooms1 and subjected to refrigeration with a view to ridding them entirely of their body heat4 ,the coolers are large rooms fitted with brine pipes and capable of accommodating several hundred carcasses4 ,the temperature of the coolers when the carcasses are run in is about #cb ,f4 ,when filled1 the temperature of the cooler rises to about #de ,f41 owing to the heat given off from the carcasses4 ,the temperature is then gradually reduced to #bh or #cj ,f4 ,hog carcasses are left in the coolers as a rule for forty-eight hours1 at the end of which time they are stiff and firm1 but not frozen4 ,the temperature of the chill rooms is always carefully watched1 thermometer readings being made every few hours and duly recorded4 ,the temperature of the carcasses is always tested when they leave the chill room4 ,in those plants provided with a hanging floor1 a certain number of the carcasses are also tested before they are sent to the chill rooms in order to determine the amount of heat lost on the hanging floor4 ,the carcasses are tested by means of an especially constructed thermometer1 known as a 8ham thermometer10 which has a pointed metal protector so that it can be thrust into the body of the ham4 7,see fig4 #d47 ,the ham has been rightly selected as the proper portion of the carcass at which to take the temperature1 as it constitutes the largest mass of muscular tissue in the carcass and holds the body heat longer than any other portion4 ,in taking the temperature1 the thermometer is thrust deep into the body of the ham so that the point of the thermometer rests alongside or a little behind the upper portion of the femur or middle bone1 the latter being used as a guide in introducing the thermometer4 ,a certain number of the carcasses from each cooler are tested in this way as a check on the refrigeration4 ,the inside temperature of the hams when they leave the chill rooms should be about #cd ,f4 ,the carcasses are next cut up and the hams trimmed for pickling4 ,in some houses the hams are given an additional chilling of #dh hours after they are cut from the carcasses1 but this is not done as a rule1 nor does it seem to be necessary4 ,the hams are now sent to the pickling rooms1 or 8sweet pickle department10 as this branch of the packing house is designated1 and here a certain number are again tested with a thermometer1 as described above4 ,this test is carried out by the foreman in charge of the sweet pickle department in order that he may satisfy himself that the hams are properly chilled before they go into the pickle and as an additional check on the refrigeration4 ,the hams are now ready to be 8pumped10 and this pumping1 as will be shown later1 constitutes an important step in a successful cure4 ,pumping consists in forcing a strong brine solution containing saltpeter into the muscular tissues of the ham1 and is accomplished by means of a large1 hollow1 fenestrated needle connected by means of a rubber hose with a powerful hand pump4 ,the needle is introduced along the bone1 the latter being used as a guide4 ,in all of the larger packing establishments two general methods of curing hams are followed1 the two methods being designated as the 8fancy0 or 8mild cure0 and the 8regular cure10 the term 8cure0 being used to designate the curing period4 ,various trade names are given by the different packing establishments to the hams cured by these methods4 ,in the fancy cure the hams are pumped in the shank only1 whereas in the regular cure they are pumped in both body and shank4 ,the same pumping pickle is generally used for the two cures4 ,it is a significant fact that the greater proportion of the 8sours0 are found among the fancy or mild cure hams4 ,this point will be discussed farther on in connection with some experiments to be described later4 ,the actual curing is usually carried out in large vats which hold about #a1djj pounds of meat or some hundred hams4 ,the hams are packed in the vats in layers and are entirely covered with the pickling solution or brine4 ,a certain proportion is always observed between the weight of the meat and the amount of the solution4 ,the pickling solution1 or 8pickle10 as it is termed1 is a brine solution containing saltpeter and sugar4 ,the composition of the pickle varies somewhat with the different packing establishments4 ,the fancy-cure hams are usually cured in a milder pickle1 that is1 one that contains less salt and saltpeter than the pickle used in the regular cure1 although in some packing establishments the same curing pickle is used for the two cures1 the only difference being the additional pumping given the regular-cure hams4 ,the pickling rooms1 or 8cellars10 as they are called1 are held at a temperature of #cd to #cf ,f41 and the pickling solutions are always chilled to this temperature before being used4 ,the hams are allowed to remain in cure for about #fj days1 and during this time are 8overhauled0 several times4 ,overhauling consists in throwing the hams from the vat in which they are packed into a neighboring empty vat1 and then transferring the pickle to the new vat4 ,the pickle is not changed1 and the same pickle follows the hams through the entire curing process4 ,the object in overhauling is to stir up the pickle and expose fresh surfaces of the meat to its action4 ,hams are also cured in tierces which hold about #cjj pounds of meat4 ,in the tierce cure1 the hams are packed in the tierces1 the latter are then headed up1 the pickling solution is next run in through the bunghole1 so as to fill the tierce entirely1 and a wooden stopper is finally driven into the bunghole4 ,the tierces are rolled back and forth across the floor on dates corresponding to the dates of overhauling in the vat cure4 ,the object of the rolling is to stir up the pickle1 and in this way it corresponds to overhauling in the vat cure4 ,,definition ,,of ,,souring4 ,to the meat inspector1 a sour ham is one which has a tainted or 8off0 odor1 that is1 any odor which deviates from the normal4 ,the odor may be very slight1 so slight that at times only the trained meat inspector can detect it4 ,when slight1 the odor is elusive and hard to define1 but when pronounced it has a distinctly putrefactive quality4 ,when not very pronounced1 the odor possesses1 as a rule1 a slightly sour quality1 chemically speaking1 and at times this sour quality may be quite marked2 hence the term 8sour ham10 or 8sour0 has originated4 ,in a badly soured ham--using the term 8sour0 in the packing-house sense to denote any ham that is tainted--the odor loses this sour quality and becomes distinctly putrefactive in nature4 ,,classification ,,of ,,sour ,,hams ,,and ,,location ,,of ,,sour ,,areas4 ,sour hams are classed as 8shank sours0 and 8body sours10 according to the location of the souring1 and these may be 8light0 or 8heavy40 ,when the souring is very pronounced1 the ham is termed a 8stinker40 ,souring appears to start1 as a rule1 around the stifle joint 7femorotibial articulation71 and extends upward into the body of the ham4 ,in quite a large proportion of the hams which are sour in the body--probably from #dj to #ej per cent--the souring extends through to the bone marrow of the femur or middle bone1 and the sour odor is at times more pronounced in the bone marrow than in the meat4 ,the odor of the bone marrow1 when pronounced1 is strongly suggestive of a dissecting-room odor1 and is distinctly putrefactive in quality4 ,in the case of light body sours the sour odor is confined to a small area immediately around the bone1 and may be so slight that it is detected only with difficulty4 ,in such hams the bone marrow is apt to be sweet1 and it is not until the souring becomes more extensive that the bone marrow becomes involved4 ,illustration3 ,,fig4 #a4--;,cross section through body of ham1 with sour areas indicated by shading and dotted lines4 ,the distribution of the sour area in the body of a well-developed sour is shown in figure #a4 ,in the case of a well-developed body sour the sour area is more pronounced near the bone1 as represented in figure #a by the shaded area1 and may extend out into the body of the ham for a variable distance1 according to the degree of souring1 as represented by the dotted lines1 gradually fading off toward the margins1 where it may be imperceptible or entirely wanting4 ,in the pronounced sours1 termed 8stinkers10 the odor pervades the entire ham1 and is of a distinctly putrefactive quality4 ,in shank sours1 the souring is more or less confined to the shank1 or the region about the tibio-femoral articulation1 but may extend upward into the lower portion of the body of the ham4 ,,method ,,of ,,detecting ,,sour ,,hams4 ,souring is detected and located by means of a pointed metal instrument known as a 8ham trier10 which resembles a long1 slightly flattened ice pick4 ,the trier is thrust into the ham at different points along the bone1 rapidly withdrawn1 and the odor which clings to the metal noted4 ,the trained inspector works very rapidly1 and is able to detect even the slightest sour or off odor which might be imperceptible to one not trained to the work4 ,at the end of the cure all hams are tested with the trier under the supervision of ,government meat inspectors4 ,hams are also given what is called the 8#cj-;day inspection0 by plant inspectors during the process of curing4 ,an average ham weighing from #ad to #af pounds requires about #fj days to cure1 and at the end of #cj days a certain number of hams in each run are usually tested to see how the cure is progressing4 ,if no sour hams are discovered at this inspection the packer knows that the cure is progressing satisfactorily1 and moreover he feels sure that his hams will finish satisfactorily1 for experience has taught him that souring develops within the first four weeks of the curing period1 and if his hams are sweet at the end of this time1 he can feel practically sure that no sours will develop later on4 ,,theories ,,in ,,regard ,,to ,,ham ,,souring4 ,the theories as to the cause of souring are many and varied4 ,the majority of them are pure speculation and have no foundation upon observed facts4 ,a few of these theories may be enumerated to show how wide and varied has been the speculation upon this subject4 ,a theory which is quite prevalent among packing-house employees attributes souring to overheating of the animal previous to slaughter1 but tests were made by driving hogs to the point of exhaustion just prior to slaughter and curing the hams from these animals in comparison with hams taken from animals which had been rested prior to slaughter1 with no difference in the cured product2 that is1 the hams taken from overheated hogs cured equally as well as those taken from rested hogs4 ,another theory attributes souring to a diseased condition of the meat4 ,prior to the enforcement of the ,federal regulations governing meat inspection there might have been some ground for such a supposition1 but this theory could not hold at the present time1 in view of the thorough and efficient inspection now in force1 for it can be safely said that no diseased meat now passes the ,government inspectors1 and therefore no diseased meat goes into cure in inspected houses4 ,in order to test this theory1 however1 hams were secured from a number of condemned animals which showed various diseased conditions1 such as hog cholera1 pyemia1 septicemia1 scirrhous chord1 etc41 and these hams were cured in comparison with hams taken from normal hogs4 ,it was found that the hams taken from the diseased hogs cured equally as well as those taken from healthy hogs4 ,the hams from the diseased hogs were destroyed after the experiment1 as the meat taken from diseased animals was of course not considered fit for consumption1 the object of the experiment being merely to determine whether or not souring is caused by diseased conditions4 ,another theory attributes souring to imperfect or too rapid chilling of the meat before it is put in pickle1 and places the blame upon the refrigeration4 ,according to this theory1 souring results when the meat is chilled too suddenly1 the idea being that by the rapid congealing of the juices of the meat a coating is formed on the outside of the ham whereby the animal heat is prevented from escaping from the interior1 leaving the meat next to the bone at a higher temperature than the outside of the ham4 ,in order to test this last theory1 a number of hog carcasses were run direct from the killing floor to a cooler at #bh ,f4 and a like number of carcasses of the same average weight which had been allowed to stand for two hours at the outside temperature of the air 7#ec ,f47 were placed in the same cooler4 ,the carcasses which had hung for two hours in the air had lost an average of #ad degrees in temperature before going to the cooler4 ,the temperature of the cooler rose to #bi ,f4 after the carcasses were put in1 but was soon reduced to #bh ,f4 and held at this temperature4 ,the temperatures of the hams were taken at the end of #bd hours1 and practically no difference was found in the inside temperatures of the two lots2 that is1 the hams on the hot carcasses which were subjected to a sudden chilling exhibited practically the same inside temperature 7i4 e41 next to the bone7 as those which had cooled for two hours at the temperature of the air before being placed in the cooler4 ,still another theory attributes souring to lack of penetration of the pickling fluids1 but analyses of sour and sound hams do not seem to bear out this theory4 ,the rate of penetration of the pickling fluids1 however1 would seem to have some bearing on the subject1 and this point will be discussed later in connection with some laboratory experiments on the inhibitory effects of sodium chlorid and potassium nitrate4 ,so much for the more commonly accepted theories which have been advanced to explain ham souring4 ,,previous ,,experimental ,,work ,,to ,,determine ,,cause ,,of ,,ham ,,souring4 ,a review of the literature reveals but one article bearing directly on the subject of the cause of ham souring4 ,in ,june1 #aijh1 ,klein#a published in the ,london ,lancet an article on 8miscured0 hams4 ,he describes a miscured ham as one which has a distinctly putrid smell1 and the tainted areas he describes as varying in color from a dirty gray to a dirty green1 the muscular tissues in the strongly tainted areas being swollen and soft1 or jelly-like4 ,from such hams he isolated a large nonmotile1 nonspore-bearing1 anaerobic bacillus which he calls ,bacillus fdans4 ,he cultivated the organism on different media and obtained from the cultures a putrid odor resembling that of the ham from which the culture was obtained1 but did not attempt to produce tainting by injecting sound hams with the bacillus4 #a ,klein1 ,e4 ,on the nature and causes of taint in miscured hams4 ,the ,lancet1 vol4 #agd1 ,london1 ,june #bg1 #aijh4 ,while there can be little doubt that ,klein's bacillus was the cause of the tainting in those hams which he examined1 the proof would certainly have been stronger had he injected sound hams with cultures and thus proven that he could reproduce tainting experimentally by means of his bacillus4 ,klein examined only dry-cured hams and does not state the temperature at which they were cured4 ,he fails to offer any explanation as to how the bacillus gained entrance into the hams4 ,,the ,,present ,,experiments4 ,,media ,,employed4 ,after considerable experimentation as to a suitable culture medium for the bacteriological study of sour hams1 a modification of the 8egg-meat mixture0 used by ,rettger#b in his studies on putrefaction was found to be the most satisfactory4 ,this medium1 which consists of chopped meat and egg albumen1 furnishes an excellent medium for the growth of putrefactive organisms which rapidly break down the proteids of the meat1 giving rise to the characteristic odors of putrid decomposition4 ,rettger used chopped beef and egg albumen1 but for the present work chopped pork was substituted for the beef1 as affording a more suitable medium for the growth of organisms accustomed to growth in pork hams4 ,the modified medium is prepared as follows3 ,a4 ,one-half pound of lean pork1 freed from excess of fat and sinew1 is finely chopped in a meat chopper1 #bej cubic centimeters of water is then added1 the meat acids are neutralized with sodium carbonate1 and the mixture is heated in an ,arnold sterilizer for #cj minutes1 with occasional stirring4 ,it is then set away in a cold place for several hours4 ,a small amount of fat collects at the top in the form of a fatty scum1 as it is impossible to remove all of the fat from the meat before it is chopped4 ,the fatty scum1 which hardens upon standing in the cold1 is now removed4 ,b4 ,the whites of three eggs are mixed with #bej cubic centimeters of water4 ,the mixture is rendered neutral to phenolphthalein by means of dilute hydrochloric acid and heated for #cj minutes in the ,arnold sterilizer1 with occasional stirring4 ,a and ,b are now mixed and #b4e grams 7#j4e per cent7 of powdered calcium carbonate added4 ,the mixture is next run into large sterile test tubes1 or sterile flasks1 and sterilized in an ,arnold sterilizer on three successive days4 #b ,rettger1 ,l4 ,f4 ,studies on putrefaction4 ,journal of ,biological ,chemistry1 vol4 #b1 #aijf4 ,in addition to the egg-pork mixture described above1 culture tubes of agar and bouillon prepared from pork instead of beef1 with the addition of #a per cent of glucose1 were also used2 but the best results were obtained with the egg-pork medium1 as with this medium1 the early development of sour or putrefactive odors furnished a valuable indication as to the presence of organisms capable of producing sour or putrefactive changes in meat4 ,,method ,,of ,,procedure ,,in ,,examining ,,hams4 ,the hams were sectioned through the body1 the femur1 or 8middle bone10 as it is known in packing-house parlance1 being cut at a point about #a or #b inches below its head4 ,a cross section of a ham thus cut is shown in figure #a4 ,after sectioning1 the hams were subjected to a microscopical1 bacteriological1 and chemical examination as follows3 ,microscopical examination4--,bits of muscular tissue1 taken from various points1 were teased out in salt solution and the condition of the muscle fibers noted4 ,smear preparations were also made from bits of muscular tissue and from the bone marrow1 and these were stained and subjected to microscopical examination4 ,portions of the meat were also hardened and cut into microscopic sections1 which were stained and mounted for histological and bacteriological study4 ,bacteriological examination4--,in the bacteriological examination of sour hams1 especial attention was directed to the detection of anaerobic species1 as it seemed reasonable to suppose that if the changes taking place in sour hams were due to bacteria these bacteria would in all likelihood be anaerobes 7i4 e41 organisms which develop in the absence of oxygen74 ,this assumption was based upon the fact that1 as a rule1 souring begins in the interior of the ham next to the bone1 and1 furthermore1 the hams are cured in large vats where they are completely submerged in the pickling fluids1 so that any bacteria which develop within the bodies of the hams while they are in cure are probably restricted to practically anaerobic conditions4 ,cultures were made from the interiors of the hams at various points by first searing the cut surface thoroughly with a heavy metal spatula and then cutting out1 by means of sterile scissors and forceps1 plugs of meat about #a cm4 square4 ,the plugs of meat were then dropped into tubes containing the egg-pork medium and pushed down to the bottom of the tubes1 where they were held in place by the chopped meat above2 in this way conditions favorable for the development of anaerobic organisms were obtained4 ,in inoculating the pork-agar tubes1 the medium was first boiled to expel any inclosed air and cooled to #dc to #de ,c2 the plugs of meat were then dropped into the tubes and the agar rapidly solidified by plunging the tubes in cold water2 in this way the bits of meat were inclosed in the agar at the bottom of the tubes1 affording suitable conditions for anaerobic growth4 ,aerobic and anaerobic plates were also made from the meat1 and in most cases bouillon tubes were also inoculated4 ,cultures were always taken from the bone marrow as well as from the meat4 ,novy jars were also used for obtaining anaerobic conditions in growing the cultures4 ,chemical examination4--,in order to determine whether the souring was connected with or dependent upon a lack of penetration of the pickling fluids to the interior of the meat1 the hams were further subjected to a chemical examination and the content of the meat in sodium chlorid and potassium nitrate determined at varying depths4 ,,results ,,of ,,examination ,,of ,,sour ,,and ,,sound ,,hams4 ,the sour hams examined were obtained from four different packing establishments4 ,all of the hams studied were 8sweet-pickle hams0 which had not been smoked4 ,the sour hams selected for examination were good typical body sours1 in which the sour odor was well developed1 but not of the very pronounced or putrefactive type4 ,the sour odor in every case was found to be more pronounced next to the bone1 being usually rather more pronounced just behind the bone1 that is1 on the fat side of the bone4 ,the sour odor in each instance was confined to an area of meat immediately surrounding the femur and extending out through the body of the ham for a variable distance1 as shown by the dotted lines in figure #a1 but in no case did the sour odor extend all the way to the margin of the meat1 nor did it as a rule extend below the tibio-femoral articulation1 the shank proper and the bone marrow of the shank 7i4 e41 of the tibia7 being usually sweet4 ,the butt portion of the hams--that portion above and behind the hitch bone 7symphasis pubis7--was also sweet4 ,immediately after sectioning1 the sour areas1 as a rule1 could be readily distinguished by a difference in color4 ,in the freshly cut hams the muscular tissue near the bone1 where the sour odor was more pronounced1 exhibited a slight but distinct grayish hue1 at times having a slight greenish tinge2 in other words1 the muscular tissue in the sour areas lacked the normal bright red color of the sound meat and was distinctly lighter in color than the surrounding tissues4 ,upon exposure to air1 however1 the lighter1 grayish1 sour areas tend to assume a reddish hue and become much less pronounced than in the freshly cut ham4 ,after the cut surface of the ham has been exposed to the air for some time it may be difficult to distinguish the sour areas by any difference in color4 ,illustration3 ,,bul4 #acb1 ,,bureau ,,of ,,animal ,,industry1 ,u4 ,s4 ,,dept4 ,,of ,,agriculture4 ,,plate ,i4 ,,fig4 #a4--,,section ,,of ,,muscular ,,tissue ,,from ,,sound ,,ham1 ,,showing ,,muscle ,,fibers ,,cut ,,longitudinally2 ,,nuclei ,,sharply ,,defined ,,and ,,cross ,,striation ,,distinct4 7,pen-and-ink drawing made with camera lucida from section stained with hematoxylin and eosin to show histological structure4 #cbj47 ,,fig4 #b4--,,section ,,of ,,muscular ,,tissue ,,from ,,sour ,,ham1 ,,showing ,,muscle ,,fibers ,,cut ,,longitudinally2 ,,nuclei ,,undergoing ,,disintegration ,,and ,,cross ,,striation ,,indistinct4 7,pen-and-ink drawing made with camera lucida from section stained with hematoxylin and eosin to show histological structure4 #cbj47 ,illustration3 ,,bul4 #acb1 ,,bureau ,,of ,,animal ,,industry1 ,u4 ,s4 ,,dept4 ,,of ,,agriculture4 ,,plate ,,ii4 ,,fig4 #a4--,,section ,,through ,,muscular ,,tissue ,,of ,,ham ,,which ,,has ,,undergone ,,natural ,,or ,,spontaneous ,,souring1 ,,showing ,,distribution ,,of ,,bacilli ,,between ,,the ,,muscle ,,fibers1 ,,which ,,are ,,cut ,,obliquely4 ,,the ,,dark ,,masses ,,between ,,the ,,muscle ,,fibers ,,represent ,,clumps ,,of ,,bacilli4 7,pen-and-ink drawing made with camera lucida from section stained by the ,gram-,weigert method to show bacteria4 #he47 ,,fig4 #b4--,,section ,,through ,,muscular ,,tissue ,,of ,,ham ,,which ,,has ,,undergone ,,natural ,,or ,,spontaneous ,,souring1 ,,showing ,,individual ,,bacilli ,,between ,,the ,,muscle ,,fibers1 ,,which ,,are ,,cut ,,somewhat ,,obliquely4 ,,nuclei ,,have ,,lost ,,sharp ,,outline ,,and ,,cross ,,striation ,,is ,,indistinct4 7,pen-and-ink drawing made with camera lucida from section stained by the ,gram-,weigert method to show bacteria4 #cbj47 ,in the sour areas near the bone the muscular tissue was distinctly softer2 that is1 it broke and cut more readily than the surrounding tissues4 ,this was usually quite noticeable in cutting out plugs of the meat for making cultures4 ,in a ham which shows pronounced souring the muscular tissues in the worst affected areas may become quite soft and even slightly gelatinous4 ,the sour areas1 when tested with litmus paper1 frequently showed a slight but distinct alkaline reaction4 ,when aqueous extracts of the sour meat1 however1 were titrated with phenolphthalein they were found to be acid4 ,,histological ,,changes ,,in ,,sour ,,hams4 ,in preparations made by teasing out bits of the meat in physiological salt solution1 the cross striation of the muscle fibers from the sour areas was found to be much less distinct than in similar preparations taken from sound portions of the meat or from sound hams4 ,at times it was found that the muscle fibers in the sour areas had completely lost their cross stri1 but the longitudinal striation could still be made out4 ,in cases where the souring was pronounced there was sometimes complete loss of both longitudinal and cross striation2 in these cases the muscle fibers appeared to have undergone slight swelling and the protoplasm exhibited a finely granular appearance4 ,in stained sections of the sour meat another striking change was noticed in the disintegration of the nuclei of the muscle fibers1 which are at times completely broken up1 appearing as bluish granular masses in sections stained with hematoxylin and eosin4 7,compare figs4 #a and #b of ,pl4 ,i47 ,in sections stained by the ,gram-,weigert method to show the presence of bacteria1 a large ,gram-staining bacillus was noted between the muscle fibers in the connective-tissue elements of the muscle4 ,in some of the sections these bacilli were present in great numbers1 sometimes in densely packed clumps or masses1 while in other sections1 or in other portions of the same section1 they were only sparsely distributed between the muscle fibers4 ,where the bacteria were more numerous the histological changes in the muscle fibers1 especially the breaking down of the nuclei1 were more noticeable4 ,the intermuscular connective tissue had apparently furnished paths of least resistance along which the organism followed4 ,in ,plate ,,ii1 figures #a and #b1 the bacteria are shown between the muscle fibers under low and high power magnifications4 ,in ,plate ,,ii1 figure #a1 under the low-power magnification1 the bacteria appear as dark clumps or bands between the muscle bundles4 ,under the high power they are shown following along the sarcolemma sheaths between the muscle fibers4 ,,chemical ,,analyses ,,of ,,sour ,,and ,,sound ,,hams4 ,in order to determine whether there was any difference in regard to the penetration of the pickling fluids in the sour hams as compared with sound hams1 a series of four sour hams were subjected to a chemical examination in comparison with four sound hams4 ,all were sweet-pickle hams and were obtained from the same packing establishment4 ,they were all of the same cure and the same approximate age 7i4 e41 length of cure7 and the same approximate weight4 ,in taking samples for chemical analysis1 the following procedure was adopted3 ,a section about #b inches wide was cut from the center of the body4 ,the two ends of this section were then trimmed off along the lines ,l-,m and ,n-,o1 as shown in figure #b4 ,beginning at the skinned surface1 four slices1 ,a1 ,b1 ,c1 and ,d1 were then made1 as indicated by the dotted lines4 ,slice ,b contained the bone in each instance4 ,slice ,d was practically all fat4 ,each slice was ground separately in a meat chopper and the sample thoroughly mixed before taking out portions for analysis4 ,illustration3 ,,fig4 #b4--;,cross section through body of ham to show method of sampling for chemical analysis4 ,a1 slice below bone2 ,b1 bone slice2 ,c1 slice above bone2 ,d1 fat slice4 ,as all of the hams examined were mild-cure hams1 that is1 had been pumped in the shank only1 the pickling fluids in order to reach the bodies of these hams had to penetrate chiefly from the skinned surface of the ham1 as little if any penetration takes place through the thick skin of the ham4 ,the analyses#c shown in the following tables therefore indicate the degree of penetration of the pickling fluids4 #c ,these analyses were made by ,mr4 ,r4 ,r4 ,henley1 of the ,biochemic ,division1 ,bureau of ,animal ,industry4 ,analyses of sour hams4 ,no4,description4,slice4 ,na,cl4 ,,kno4 ,per cent4,per cent4 #a ,sour body ,a #f4ah #j4age ,b #d4hc 4#bbd ,c #c4fe 4#bii ,d #a4jc 4#jgd #b do ,a #e4cd 4#agd ,b #c4gj 4#aej ,c #b4gi 4#agd ,d #a4ab 4#jab #c do ,a #e4jd 4#abe ,b #d4jh 4#adi ,c #b4gb 4#jii ,d #a4ai 4#jdh #d do ,a #g4gh 4#bej ,b #e4ca 4#ajj ,c #d4gf 4#bjj ,d #a4if 4#jdh ,analyses of sound hams4 ,no4,description4,slice4 ,na,cl4 ,,kno4 ,per cent4,per cent4 #a ,sound ,a #e4hj #j4baa ,b #d4hc 4#ahh ,c #c4hf 4#bba ,d #a4cc 4#jfc #b do ,a #d4id 4#aig ,b #d4jh 4#adi ,c #c4je 4#bbc ,d #a4ef 4#jei #c do ,a #e4ib 4#agc ,b #d4bi 4#jii ,c #d4ab 4#aci ,d #b4cb 4#jdi #d do ,a #e4ec 4#aai ,b #d4hi 4#jgi ,c #d4cb 4#jii ,d #b4ai 4#jda ,taking an average of the four slices in each ham so as to get an average for the entire ham1 and comparing the sour hams with the sound hams1 we have the following comparison3 ,na,cl4 ,,kno4 ,average for #d sour hams 7entire ham7 per cent4 #c4hd #j4adc ,average for #d sound hams 7entire ham7 do #c4ic 4#aca ,these figures show practically no difference between the sour and the sound hams as regards the sodium chlorid and potassium nitrate content of the entire ham4 ,if1 now1 we compare the bone slices--and these afford really a better basis for comparison1 as in sour-body hams the souring is always more pronounced around the bone--we have the following figures3 ,na,cl4 ,,kno4 ,average for #d sour hams 7bone slice7 per cent4 #d4dh #j4aee ,average for #d sound hams 7bone slice7 do #d4eb #j4abi ,here1 again1 we find no essential difference between the sour and the sound hams1 and we must conclude from these analyses that souring does not depend upon or result from a lack of penetration of the pickling fluids4 ,it seems probable that in mild-cure hams1 which are pumped in the shank only1 the souring begins in the upper portion of the shank and extends upward along the bone into the body of the ham1 and that it takes place before the pickling fluid has penetrated to the interior of the ham4 ,when the pickling fluid reaches the interior of the ham it tends to inhibit the souring1 which1 as will be shown later1 is due to the development of bacteria within the bodies of the hams4 ,the growth of the bacteria1 however1 within the bodies of the hams and the histological changes in the muscle fibers do not seem to interfere with the penetration of the pickling fluids4 ,,bacteriological ,,examination ,,of ,,sour ,,and ,,sound ,,hams4 ,in all of the sour hams which were examined bacteriologically a large anaerobic bacillus was found to be constantly present4 ,from several of the hams this bacillus was obtained in pure culture2 that is1 it was the only organism present in cultures made from the sour meat and from the bone marrow of the femur4 ,such cultures1 when held at room temperature1 gave1 at three days1 a sour-meat odor exactly resembling that obtained from sour hams4 ,in many of the sour hams other bacteria were found in association with the anaerobic bacillus noted above4 ,these other bacteria1 however1 were not constant1 being sometimes present and sometimes absent4 ,among the other bacteria noted in the sour hams1 the following forms occurred most frequently3 #a4 ,a nonmotile1 gram-positive bacillus1 measuring from #a4e to #d microns in length by #j4e micron in breadth1 sometimes in chains and filaments4 #b4 ,a small1 nonmotile1 gram-negative bacillus1 about the size of ,bacillus coli and usually in pairs4 #c4 ,a large micrococcus4 ,sometimes one and sometimes all of these bacteria were present in a given ham4 ,they were encountered most frequently in hams which had been pumped in both body and shank1 and were probably ordinary pickle bacteria4 ,they were not strict anaerobes1 but belonged to the class of facultative or optional anaerobes2 that is1 organisms which will grow either with or without free oxygen4 ,these bacteria were isolated and grown on the egg-pork medium1 but failed to give any characteristic sour or putrefactive odors1 and were therefore discarded4 ,a series of sound hams1 all of them of mild cure--that is1 hams which had been pumped in the shank only--were also examined bacteriologically4 ,in examining these hams cultures were taken at varying depths1 beginning at the skinned surface and going backward toward the fat4 ,cultures were also taken from the bone marrow of the femur4 ,in the cultures taken near the skinned surfaces the ordinary pickle bacteria were obtained1 but these did not1 as a rule1 extend beyond a depth of #c centimeters below the skinned surface4 ,the cultures taken from the deeper portions of the hams and from the bone marrow of the femur were entirely negative--that is1 failed to show any growth--and the anaerobic bacillus noted in the sour hams was not encountered in any of the cultures made from these hams4 ,the anaerobic bacillus isolated from the sour hams was found to correspond in morphology with the organism noted in the microscopic sections made from the muscular tissue4 ,in view of this fact and the fact that it was constantly present in the sour hams examined1 and was capable of producing in egg-pork cultures a sour-meat odor of the same nature as that obtained from sour hams1 this organism was subjected to further study and experimentation4 ,,inoculation ,,experiments ,,with ,,hams4 ,the experiments which follow were conducted at two different packing establishments in one of the larger packing centers of the country4 ,the officials at each of these establishments showed great interest in the experiments and were most courteous and obliging in supplying the necessary materials4 ,the first question to be decided was whether the bacillus isolated from sour hams was actually capable of causing ham souring4 ,the bacillus in question had1 when cultivated on the egg-pork medium1 given rise to a sour odor similar to that obtained from sour hams1 but this was not regarded as proof positive that the organism was the actual cause of souring in hams4 ,the proper way to decide this point seemed to be to inoculate hams with the bacillus and then subject these hams to the regular method of cure and see whether they became sour1 just as the pathogenic properties of a disease-producing organism are determined by the inoculation of experiment animals4 ,the first two experiments which follow were designed to decide this point4 ,it was regarded as important to conduct similar experiments at two different establishments1 in order to determine whether the same results would be obtained under the somewhat different conditions imposed by different methods of cure4 ,the two experiments which follow were carried out1 therefore1 at different establishments4 ,experiment ,i4 ,in carrying out this experiment four tierces of hams were 8put down0 or 8packed0--that is1 placed in cure4 ,two of the tierces were given the fancy or mild cure and two the regular or stronger cure4 ,the hams in two of the tierces1 one mild and one regular cure1 were injected with a culture suspension of the bacillus2 the other two tierces were not injected with culture and were put down to serve as checks on the cure4 ,hams weighing from #ab to #ad pounds were used for the mild cure1 while for the regular cure hams weighing from #ad to #af pounds were used4 ,this was in accordance with the general rule which prevails in packing houses1 the lighter hams being subjected to the mild cure and the heavier hams to the regular cure4 ,the only difference between the mild and the regular cure in this experiment lay in the pumping4 ,the hams which were given the mild cure were pumped in the shank only1 while those given the regular cure were pumped in the body as well as in the shank4 ,all of the hams had received the usual #dh-;hour chill4 ,they were all pumped with the same pumping pickle and cured in the same curing pickle1 and were in cure for the same length of time4 ,the pumping and curing pickles used were the regular pumping and curing pickles of the establishment at which the experiment was carried out1 and the hams were cured in accordance with the fancy and regular cures as practiced at this establishment4 ,the hams were packed in new tierces which had been thoroughly scalded with boiling water4 ,the tierces were held in a curing room which was kept at an average temperature of from #cd to #cf ,f41 the temperature occasionally going as high as #ch and #dj ,f41 but never above #dj ,f4 ,the hams were left in cure for about #gj days1 which is a little longer than the usual cure4 ,the tierces were rolled three times during the cure4 ,at the end of the cure the hams in all four tierces were carefully tested by an expert meat inspector1 who knew nothing of the treatment which the hams had received4 ,the hams in two of the tierces were inoculated with a culture suspension prepared as follows3 ,ten tubes of egg-pork medium1 each tube containing approximately #aj cubic centimeters of the medium1 were inoculated with the bacillus and held at room temperature 7#bj to #be ,c47 for six days4 ,the cultures were then filtered through sterile gauze into a large sterile flask2 this was done in order to remove the particles of meat1 which might otherwise have clogged the syringes used in inoculating the hams4 ,in transferring the contents of the culture tubes to the filter the tubes were washed out with sterile physiological salt solution 7#j4f per cent sodium chlorid71 and the meat particles on the filter were afterwards washed with the salt solution1 a sufficient quantity of the latter being used to bring the total volume of filtrate to #djj cubic centimeters4 ,a microscopic preparation from the filtrate showed the organisms in large numbers1 with an occasional rod showing a large terminal spore4 ,this suspension was used for the injection of #dj hams1 each ham being given #aj cubic centimeters1 or the equivalent of #b4e cubic centimeters of the original culture4 ,the hams were injected with the culture suspension by means of a sterile syringe carrying a long #e-;inch needle4 ,the needle was thrust well into the body of the ham at a point near the upper end of the middle bone or femur1 the latter being used as a guide in inserting the needle and the injection being made into the tissues just behind and a little to one side of the upper end of the femur4 ,the details of the experiment were as follows3 ,tierce ,no4 #a 7fancy cure74--,this tierce contained #bj hams weighing from #ab to #ad pounds each4 ,these hams were pumped in the shank only4 ,immediately after pumping they were injected with #aj cubic centimeters each of the liquid culture or suspension described above4 ,after injection the hams were immediately packed in the tierce1 which was then headed up1 filled with the regular curing pickle1 and placed in cure4 ,result3 ,when tested at the end of the cure all of the hams in this tierce save one were found to be sour4 ,in #aj of them the souring was very marked throughout the body of the ham and extended into the shank as well4 ,in six the souring was very marked in the body of the ham1 but did not extend into the shank4 ,in three there was slight but well-marked souring in the body of the ham with no souring in the shank1 and one remained sweet4 ,the probable explanation of the variation in the degree and the extent of the souring will be discussed later4 ,the bone marrow of the femur or middle bone was tested in all of the hams and found to be sour in #ah4 ,in one of the hams which showed only slight souring in the body the souring did not extend through to the bone marrow1 and in the ham which remained sweet the bone marrow was also sweet4 ,the fact that one ham in this tierce remained sweet was in all likelihood due to an oversight in making the inoculations4 ,in making the inoculations the hams were spread out in a row on a table by a packing-house assistant1 who removed the hams as soon as they were inoculated and placed them in tierces2 and it is more than probable that the assistant removed one of the hams before it was inoculated in the interval when the writer was busy filling the syringe for the next inoculation4 ,tierce ,no4 #b 7fancy cure74--,this tierce contained #bj hams of the same average weight as the preceding4 ,they were pumped in the shank only1 but were not injected with culture1 being put down to serve as checks on the hams in tierce ,no4 #a4 ,these hams1 therefore1 were subjected to exactly the same cure and were held under exactly the same conditions as those in tierce ,no4 #a1 the only difference being that the hams in this tierce were not injected with culture4 ,result3 ,when tested at the end of the cure all of the hams in this tierce were found to be perfectly sound and sweet1 showing that the curing in this instance was properly carried out and that the souring of the hams in tierce ,no4 #a was undoubtedly due to the injections of culture which they received4 ,tierce ,no4 #c 7regular cure74--,this tierce contained #bj hams weighing from #ad to #af pounds each4 ,these hams were pumped in the shank and also in the body4 ,immediately after pumping they were each injected in the same manner as those in tierce ,no4 #a with #aj cubic centimeters of culture4 ,the hams were then packed in tierce and placed in cure4 ,result3 ,at the end of the cure #i of the hams were found to be sour1 while #aa remained sweet4 ,of the #i hams which became sour1 #a showed very pronounced souring in the body and in the shank as well1 #c showed very pronounced souring in the body1 #a showed pronounced souring in the body1 and #d slight souring in the body4 ,the bone marrow of the femur was tested in all of the sour hams and was found to be sour in #g4 ,in #b of the sour hams which showed slight souring in the body the souring noted in the meat had not extended through to the bone marrow4 ,tierce ,no4 #d 7regular cure74--,this tierce contained #bj hams of the same average weight as those in tierce ,no4 #c1 and1 like the latter1 were pumped in both shank and body1 but were not injected with culture4 ,this tierce was put down to serve as a check on tierce ,no4 #c and was held under exactly the same conditions1 the only difference being that these hams were not injected with culture4 ,result3 ,at the end of the cure the hams were carefully tested and all were found to be perfectly sound and sweet4 ,results of ,experiment ,i4 ,no4 of ,number ,average ,cure4 ,how pumped4 tierce4of hams4 weight of hams4 ,pounds4 #a #bj #ab-ad ,fancy ,shank only #b #bj #ab-ad do do #c #bj #ad-af ,regular ,shank and body #d #bj #ad-af do do ,condition at end of cure ,no4 of ,treatment ,number of ,percentage of tierce4 sour hams sour hams #a ,each ham injected #ai #ie with #aj c4c4 of culture4 #b ,not injected with #j #j culture2 check on tierce #a4 #c ,each ham injected #i #de with #aj c4c4 of culture4 #d ,not injected with #j #j culture2 check on tierce #c4 ,three hams from each tierce were selected for bacteriological and histological examination4 ,from tierces #a and #c1 which contained the injected hams1 three of the most pronounced 8sours0 were selected from each tierce4 ,in examining the hams bacteriologically the following method was adopted3 ,the hams were sectioned near the center of the body and the larger or butt end turned up so as to expose the cut surface4 ,a cross section of a ham thus cut is shown in figure #c4 ,cultures were taken at the points indicated by the numbers and from the exposed bone marrow of the femur by first searing the surface1 and then taking out plugs of the meat or marrow by means of sterile instruments4 ,the plugs of meat or marrow were dropped into tubes containing egg-pork medium and pushed to the bottom of the tubes by means of a sterile platinum wire4 ,in the cultures made from the sour hams from tierces #a and #c1 which were injected with culture1 the bacillus with which these hams were injected was found in practically every culture1 although it was sometimes absent in the cultures taken at points near the skinned surfaces of the hams 7i4 e41 at points #a1 #d1 and #e in fig4 #c74 ,in the cultures taken from the meat1 the bacillus was not always present in pure culture1 but this is not to be wondered at when we remember that the pickling fluids often contain large numbers of bacteria of various kinds1 and these1 of course1 find their way into the hams in the pickling fluids4 ,especially is this true of the hams which are pumped in the body1 where bacteria are actually pumped into the bodies of the hams in the pumping pickle4 ,in the case of hams which are not pumped in the body1 the pickle bacteria do not appear to penetrate the body of the ham to any great depth4 ,in figure #c the plus signs after the figures represent the distribution of the sour-ham bacillus in one of the hams from tierce #a1 and this may be taken as a typical example of the other sour hams which were examined in this experiment4 ,it should be explained that the shaded areas are not intended to represent the actual limits of souring1 but simply the areas in which the sour odor was most pronounced and from which it could be readily obtained with the trier4 ,in comparing the regular and mild cure hams1 it was found that the areas of souring as defined with the trier were more restricted in the regular cure hams1 and this was undoubtedly due to the additional pumping which these hams received1 whereby the growth of the bacillus was partially inhibited4 ,illustration3 ,,fig4 #c4--;,cross section through body of artificially soured ham1 showing sour areas and points at which cultures were taken4 ,darker shading indicates sour area in hams pumped in body and shank2 light shading indicates sour area in hams pumped in shank only2 figures indicate points at which cultures were taken2 plus signs indicate presence of bacillus2 minus sign indicates absence of bacillus2 ,x indicates point of inoculation4 ,it will be noticed that the sour-ham bacillus was present in cultures taken at points outside the shaded areas1 indicating that the organism had extended generally throughout the bodies of the hams4 ,as the hams were inoculated at a point just to one side of and a little behind the femur 7i4 e41 at the point ,x in the figure71 the presence of the bacillus generally throughout the hams would indicate a very extensive multiplication of the original bacilli with which the hams were injected4 ,in view of the fact that the bacillus in question is nonmotile1 the spread of the bacilli throughout the hams must result simply from subdivision and growth by extension1 and in spreading throughout the hams the bacilli appear to follow along the connective tissue bands which afford paths of least resistance4 ,in the cultures made from the bone marrow the bacillus was recovered in pure culture from each of the hams examined1 and it is probable that the bacillus finds its way into the bone marrow from the meat by following along the small arteries which pass through the bone4 ,the fact that the bacillus was found in pure culture 7i4 e41 uncontaminated7 in the cultures made from the bone marrow is explained probably by its capacity for growth by extension1 and also by the fact that the pickling solutions probably do not reach the bone marrow until late in the curing and then only to a limited extent4 ,the bacteria which ordinarily occur in pickling fluids are not strict anaerobes and are not placed under the most suitable conditions for growth when they reach the interior of the ham1 for it seems probable that in the interior of hams which are totally submerged in pickling fluids the amount of available oxygen must be extremely small4 ,the ordinary pickle bacteria1 therefore1 would not multiply as rapidly in the interior of the hams and would not find their way into the bone marrow as soon as would a strictly anaerobic organism4 ,pure cultures of the sour-ham bacillus1 recovered from the meat and bone marrow of the injected hams1 were compared with cultures of the original bacillus used for inoculating the hams1 and were found to be identical4 ,furthermore1 the bacillus with which the hams were injected was recovered from the injected hams at points far removed from the original point of injection1 showing that the organism had multiplied and extended throughout the bodies of the hams and that it was clearly responsible for the souring which the hams had undergone4 ,sound hams from tierces #b and #d were examined bacteriologically in the same manner as the injected hams1 and some of the cultures showed the ordinary pickle bacteria1 but in not a single instance did egg-pork cultures yield a sour odor1 and in no case could the sour-ham bacillus be demonstrated in any of these hams4 ,microscopic sections and teased preparations of the muscle fibers in salt solution were prepared from several of the sour hams in this experiment1 and these preparations showed the same histological changes and the same distribution of bacilli as noted in the natural sours4 ,in ,plate ,,iii1 figures #a and #b1 sections are shown of artificially soured hams1 that is1 hams which were artificially soured by injections of culture2 and if these figures be compared with the sections made from hams which had undergone spontaneous souring 7see ,pl4 ,,ii1 figs4 #a and #b7 the similarity in the form and distribution of the bacilli will be at once apparent4 ,illustration3 ,,bul4 #acb1 ,,bureau ,,of ,,animal ,,industry1 ,u4 ,s4 ,,dept4 ,,of ,,agriculture4 ,,plate ,,iii4 ,,fig4 #a4--,,section ,,through ,,muscular ,,tissue ,,of ,,artificially ,,soured ,,ham1 ,,showing ,,distribution ,,of ,,bacilli ,,between ,,the ,,muscle ,,fibers1 ,,which ,,are ,,shown ,,in ,,cross ,,section4 ,,the ,,dark ,,lines ,,and ,,masses ,,between ,,the ,,muscle ,,fibers ,,represent ,,clumps ,,of ,,bacilli4 7,pen-and-ink drawing made with camera lucida from section stained by the ,gram-,weigert method to show bacteria4 #he47 ,,fig4 #b4--,,section ,,through ,,muscular ,,tissue ,,of ,,artificially ,,soured ,,ham1 ,,showing ,,individual ,,bacilli ,,between ,,the ,,muscle ,,fibers1 ,,which ,,are ,,cut ,,longitudinally4 7,pen-and-ink drawing made with camera lucida from section stained by the ,gram-,weigert method to show bacteria4 #cbj47 ,summary and discussion of ,experiment ,i4--,comparing tierces #a and #b1 where the hams were pumped in the shank only1 the only difference being that the hams in tierce #a were inoculated with culture while those in tierce #b were not1 we find that in tierce #a nineteen out of twenty1 or #ie per cent1 of the hams became sour1 whereas in tierce #b all of the hams remained sweet4 ,in view of the fact that these tierces were held under exactly the same conditions1 we must conclude that the souring of the hams in tierce #a was due to the injection of culture which they received4 ,comparing tierces #c and #d1 where the hams were pumped in both shank and body1 the hams in tierce #c being injected with culture while those in tierce #d were not1 we find that in tierce #c nine out of twenty1 or #de per cent1 of the hams became sour1 whereas in tierce #d all of the hams remained sweet4 ,as the conditions of cure were the same for all four tierces1 we must again conclude that the souring of the hams in tierce #c was directly attributable to the injections of culture which they received4 ,if now we compare tierces #a and #c1 the two tierces which were injected with culture1 we find that in the case of tierce #a1 where the hams were pumped in the shank only1 #ie per cent became sour2 whereas in the case of tierce #c1 where the hams were pumped in both shank and body1 only #de per cent became sour4 ,in other words1 the percentage of souring in those hams which were pumped in the body as well as in the shank was #ej percent less than in those hams which were pumped in the shank only4 ,inasmuch as the only difference in the treatment accorded tierces #a and #c lay in the additional pumping given the hams in tierce #c1 we must conclude that the marked diminution in the percentage of souring in the case of tierce #c was undoubtedly due to the additional pumping which these hams received1 the hams being saturated at the start with the pumping pickle4 ,it will be shown later that both sodium chlorid and potassium nitrate exert an inhibitory effect upon the bacillus with which the hams were injected1 which directly bears out the foregoing conclusion4 ,in tierces #b and #d1 the two check tierces which were not injected with culture1 all of the hams were sweet at the end of the cure1 showing that the conditions under which the experiment was carried out were entirely favorable to a successful cure4 ,the sour odor obtained from the artificially soured hams in this experiment was pronounced by the meat inspector who tested the hams1 and who was entirely unaware of the treatment they had received1 to be identical with the usual sour odor which characterizes hams that have undergone spontaneous souring2 in other words1 there was no difference in odor between these artificially soured hams and natural sours4 ,with regard to the variation in the degree and the extent of the souring exhibited by the individual hams in the two inoculated tierces1 where some of the hams showed pronounced souring throughout the body and shank1 while others which had been injected with the same amount of culture showed only slight souring in the body1 several factors must be considered1 viz3 7#a7 ,differences in the reaction of the meat of the individual hams which may have exerted an influence on the growth of the bacteria with which the hams were injected4 7#b7 ,variations in the texture of the muscle fibers and connective tissue of the individual hams1 permitting in some cases a more rapid and thorough penetration of the pickling fluids to the interior of the hams1 whereby the inhibitory effect of the sodium chlorid and the potassium nitrate on the bacteria would come into play earlier4 7#c7 ,variations in pumping1 whereby more of the pickling solution was forced into some of the hams than into others4 ,probably all three of these factors would have to be taken into account in explaining the variation in the degree and extent of the souring exhibited by the injected hams4 ,with regard to the souring of the bone marrow1 we find that of nineteen sour hams in tierce #a eighteen showed sour marrows1 while in tierce #c nine sour hams showed seven sour marrows4 ,the high proportion of marrow sours is not surprising when it is recalled that of the nineteen sour hams in tierce #a the meat was markedly sour in sixteen1 while of the nine sour hams in tierce #c the meat was markedly sour in five4 ,in the case of the four sour hams in tierce #c which showed slight souring in the body1 two of these showed sour marrows1 while in two the marrows were sweet4 ,in this experiment the percentage of sour hams showing sour marrows corresponds with the percentage of marrow-sour hams found in the packing house1 where1 as has been pointed out before1 a ham which is markedly sour in the body will practically always show sour marrow1 while in hams which show only slight souring in the body the marrow is involved in about #ej per cent of the cases4 ,experiment ,,ii4 ,this experiment was essentially a repetition of ,experiment ,i1 but was carried out at a different packing establishment and under somewhat different conditions4 ,two lots of hams were injected with a culture suspension of the bacillus at different stages of the cure1 or rather at different stages in the preparation for cure1 i4 e41 7#a7 on the hanging floor1 previous to chilling1 and 7#b7 after chilling and pumping and immediately before packing4 ,three tierces1 each containing #bj hams1 were put down4 ,two of the tierces contained the hams injected with culture1 while the third tierce contained check hams which had not been treated with culture4 ,half of the hams in each tierce were pumped in the shank1 while the other half were pumped in both body and shank4 ,the same pumping and curing pickles were used for all three tierces1 and were the regular pumping and regular curing pickles of the establishment at which the experiment was carried out4 ,the hams used were all #ad to #af pounds in weight and were subjected to the usual #dh-;hour chill with an additional chill of #dh hours after they were cut from the carcass4 ,they were packed in tierces which had been thoroughly scrubbed and cleaned with boiling water4 ,the tierces were held in a pickling room at a temperature of #cc to #cf ,f41 the temperature never rising above #cf ,f41 and were rolled three times during the curing period4 ,the hams were in cure for about eighty days4 ,at the end of the cure the hams were carefully tested by a trained meat inspector1 who knew nothing of the treatment they had received4 ,the culture suspension was prepared from #bj tubes of egg-pork medium in the same manner as that used in ,experiment ,i1 the cultures being diluted with sufficient salt solution to give #djj cubic centimeters of suspension4 ,the cultures from which the suspension was prepared had grown at room temperature for ten days4 ,the suspension was examined microscopically and showed large numbers of the bacilli in the form of filaments or long chains1 with many of the individual organisms showing large terminal spores4 ,the hams were injected with the culture suspension in the same manner as those in ,experiment ,i4 ,the details of the experiment were as follows3 ,tierce ,no4 #a4--;,contained #bj hams1 each ham being injected with #bj cubic centimeters of the suspension or the equivalent of #aj cubic centimeters of the original culture4 ,the hams were injected while on the hanging floor1 before they had been cut from the carcasses and previous to chilling4 ,the carcasses were still quite warm--that is1 had lost but little of their body heat when the injections were made4 ,the carcasses1 which had been carefully tagged1 were then run into coolers and given the usual #dh-;hour chill1 after which the hams were severed from the carcasses and given an additional #dh-;hour chill in accordance with the custom of the packing house at which the experiment was carried out4 ,the hams were next pumped with regular pumping pickle1 #aj being pumped in both body and shank and #aj in shank only4 ,they were finally packed in a tierce1 which was then headed up1 filled with regular curing pickle1 and placed in cure4 ,result3 ,when tested at the end of the cure it was found that the #aj hams which were pumped in the shank only were all sour4 ,in each of them the souring extended throughout the entire ham1 in the shank as well as in the body1 and was very pronounced1 so much so that they were characterized as 8stinkers0 by the meat inspector who assisted in testing them4 ,the bone marrow of the femur or middle bone was sour in all of these hams4 ,of the #aj hams which were pumped in both body and shank #g showed well-marked souring throughout the body1 but the souring did not extend into the shank4 ,the bone marrow of the femur was found to be sour in #f of these hams1 while in #a the souring had not extended through to the bone marrow4 ,tierce ,no4 #b4--;,contained #bj hams which were chilled and pumped in exactly the same manner as those in tierce ,no4 #a4 ,these hams were injected with culture after they had been chilled and pumped1 or just before they were placed in cure4 ,the hams in this tierce1 therefore1 were injected with culture four days later than those in tierce #a4 ,the hams were injected with a bacterial suspension prepared in the same manner as that used for tierce #a1 except that the egg-pork cultures from which the suspension was prepared were #g days instead of #aj days old4 ,each ham was injected with #bj cubic centimeters of the suspension or the equivalent of #aj cubic centimeters of the original culture4 ,the hams were injected in the same manner as those in tierce #a4 ,result3 ,when tested at the end of the cure1 it was found that of the #aj hams which were pumped in the shank all were sour2 in #h of these the souring was very marked throughout the body of the ham and extended into the shank2 in all of these hams the souring had extended through to the bone marrow of the middle bone or femur4 ,of the #aj hams which were pumped in both body and shank #f were sour in the body4 ,these hams were classed by the meat inspector who examined them as 8light body sours10 and in none of them did the souring extend into the shank or through the bone into the bone marrow of the femur4 ,tierce ,no4 #c4--;,contained #bj hams which were chilled and pumped in the same manner as those in the two preceding tierces4 ,these hams were not injected with culture and were put down to serve as checks on the cure4 ,in other words1 they were pumped with the same pickling fluids1 were subjected to exactly the same cure1 and were held under precisely the same conditions as those in the preceding tierces1 the only difference being that the hams in this tierce were not injected with culture4 ,result3 ,when tested at the end of the cure1 all of the hams in this tierce were found to be perfectly sound and sweet4 ,results of ,experiment ,,ii4 ,no4 of ,number ,average ,how pumped4 tierce4 of weight hams4 of hams4 ,pounds4 #aj in shank #a #bj #ad-af #aj in body and shank #aj in shank #b #bj #ad-af #aj in body and shank #c #bj #ad-af #aj in shank #aj in body and shank ,condition at end of ,no4 of ,treatment4 cure4 tierce4 ------------------------------------ ,number ,percentage of sour of sour hams4 hams4 ,each ham injected with #bj #aj #ajj #a c4 c4 of culture prior to chilling and pumping4 do #g #gj ,each ham injected with #bj #aj #ajj #b c4 c4 of culture subsequent to chilling and pumping4 do #f #fj #c ,not injected with culture4 #j #j do #j #j ,four hams were selected from each tierce for bacteriological and histological examination4 ,from tierces #a and #b1 in which the hams were injected with culture1 #d of the sourest hams were selected from each tierce4 ,cultures were made from these hams in the same manner as described under ,experiment ,i and with the same result--that is1 the sour-ham bacillus was found throughout the bodies of the hams4 ,microscopic sections were also prepared from these hams and showed the same histological changes and the same distribution of bacilli as noted for the hams in ,experiment ,i4 ,summary and discussion of ,experiment ,,ii4--,comparing tierces #a and #b1 in which the hams were injected with culture1 with tierce #c1 where the hams were not injected with culture1 we find that in tierce #a seventeen hams 7#he per cent7 became sour and in tierce #b sixteen hams 7#hj per cent7 became sour1 whereas in tierce #c all of the hams were sweet4 ,the fact that all of the hams in tierce #c1 the check tierce1 were sweet indicates that the conditions were favorable for a successful cure2 and as all three tierces were cured under exactly the same conditions1 the only difference being that the hams in tierces #a and #b were injected with culture1 whereas those in tierce #c were not injected with culture1 we must conclude that the souring of the hams in tierces #a and #b was due to the injections of culture which they received4 ,comparing tierce #a with tierce #b1 we find that the hams in tierce #a showed more extensive souring than did those in tierce #b1 this being especially noticeable in the case of the hams which were pumped in both body and shank4 ,this difference in the extent or degree of souring was probably due to the fact that the hams in tierce #a were injected while they were still warm and before they had lost their animal heat1 the bacterial suspension thus having a better chance to become disseminated through the meat4 ,the hams in tierce #b were injected with culture after they had been chilled1 when the tissues were more or less contracted and the conditions less favorable for the dissemination of the suspension throughout the meat4 ,the hams in tierce #a were also injected four days earlier than those in tierce #b1 and prior to pumping2 and this would explain the greater difference in the extent of the souring in the case of the hams which were pumped in both body and shank1 as in tierce #a the bacteria had four days in which to develop before coming in contact with the pickling fluids1 whereas in tierce #b the bacteria were injected after the hams were pumped with pickle and were thus brought into immediate contact with the pickling fluids1 which1 as will be shown later1 have a distinct inhibitory action upon the bacillus in question4 ,in the case of the hams which were pumped in the shank but not in the body there was not this difference1 as in these hams the pickling fluids must penetrate into the bodies of the hams from the outside4 ,as it requires some time for the pickling fluids to reach the interior of a ham1 the bacteria were thus afforded quite an interval in which to develop before being exposed to the inhibitory action of the pickling fluids4 ,a chemical study of the processes involved in ham curing has been carried out in the ,biochemic ,division and the approximate rate of penetration of the curing pickle determined1 and it was found that it required about four weeks for the interior of a #aj-pound ham which had not been pumped to acquire its maximum percentage of sodium chlorid4 ,to recapitulate3 ,in this experiment #dj hams were injected with culture1 half of this number being pumped in the shank only and half in both body and shank4 ,of the #bj which were pumped in the shank only1 every ham without exception1 or #ajj per cent1 became sour4 ,of those which were pumped in both body and shank1 #ac1 or #fe per cent1 became sour4 ,the reduction in the percentage of sours in the last lot was clearly due to the additional pumping which these hams received4 ,if now we compare tierce #b in this experiment with tierces #a and #c in ,experiment ,i--these three tierces being comparable1 as they were all injected with culture at the same stage in their preparation for cure1 that is1 subsequent to chilling and pumping--we find1 in the case of the hams pumped in both body and shank1 #fe per cent of sours in ,experiment ,,ii as against #de per cent in ,experiment ,i1 and this difference is undoubtedly due to the heavier dose of culture used in ,experiment ,,ii1 where the hams were given the equivalent of #aj cubic centimeters of egg-pork culture as against #b cubic centimeters in ,experiment ,i4 ,in the case of the hams which were pumped in the shank but not in the body1 the percentage of sours was practically the same in the two experiments--in ,experiment ,i all but one of these hams became sour1 while in ,experiment ,,ii all of them became sour4 ,the degree or extent of the souring in these last hams1 however1 was greater in ,experiment ,,ii1 a result of the heavier injections of culture which they received4 ,summary of ,experiments ,i and ,,ii4 ,summarizing the results obtained in ,experiments ,i and ,,ii1 we find that culture suspensions of the anaerobic bacillus isolated from sour hams caused souring with great uniformity when injected into the bodies of sound hams which were pumped in the shank only4 ,in the two experiments1 #dj sound hams which were pumped in the shank only were injected with culture suspensions of the bacillus1 with the result that #ci1 or #ig4e per cent1 became sour during the process of cure2 and it is quite probable1 as we have pointed out before1 that one of these hams was overlooked in making the inoculations1 otherwise the entire lot would have become sour4 ,the inhibitory action of the pickling fluids upon the bacillus is well shown in the case of those hams which were pumped in both body and shank4 ,out of #dj hams which were pumped in both body and shank1 #bb1 or #ee per cent1 became sour in the process of curing4 ,inasmuch as these hams were cured under precisely the same conditions as the hams which were pumped in the shank only1 we must conclude that the diminution in souring in these hams was undoubtedly due to the additional pumping which they received1 whereby the bacteria with which these hams were injected were brought into immediate contact with the strong pumping pickle and their development thereby inhibited4 ,in these two experiments it was proven beyond doubt that the anaerobic bacillus isolated from sour hams was capable of producing souring when introduced into the bodies of sound hams2 and in view of the fact that this bacillus was constantly present in hams which had undergone spontaneous or natural souring1 and was the only organism that could be isolated from such hams that was capable of producing in egg-pork cultures the characteristic sour-ham odor1 the conclusion seems justifiable that this bacillus is an undoubted cause of the ham souring which occurs in the packing house2 and the results thus far obtained indicate that it is an important1 if not the only1 factor concerned in ham souring4 ,having established the etiological relation of the bacillus isolated from sour hams with ham souring1 the next point to be considered was the manner in which this bacillus finds its way into the bodies of the hams4 ,,probable ,,method ,,by ,,which ,,ham-,,souring ,,bacillus ,,enters ,,hams4 ,regarding the question of the probable method by which the ham-souring bacillus enters hams1 there were three possibilities to be taken into consideration3 7#a7 ,that the bacillus is present in the flesh of hogs at the time of slaughter1 7#b7 that the bacillus gains entrance through the pickling fluids1 7#c7 that the bacillus is introduced into the bodies of the hams in the handling or manipulation which the hams undergo in preparation for1 or during1 the process of curing4 ,,possibility ,,of ,,infection ,,prior ,,to ,,slaughter4 ,in order to throw some light upon this point1 a number of fresh hams--that is1 hams which had been chilled but not pumped or subjected to any other manipulation--were examined bacteriologically1 but in no case could the anaerobic bacillus which was isolated from sour hams be detected in any of them4 ,the fact that in certain of the smaller packing establishments which cure their hams without pumping the percentage of souring is extremely low would also seem to negative this possibility1 for if the bacillus which causes souring were present in the hams at the time of slaughter1 sour hams would be as frequent at such establishments as at those establishments which make a practice of pumping4 ,furthermore1 a laboratory study1 biological and chemical1 of the bacillus isolated from sour hams shows that this organism belongs to the class of putrefactive bacteria1 and while such bacteria may be present in the intestines of healthy animals1 as1 for example1 the bacillus of ,bienstock 7,bacillus putrificus71 these bacteria do not invade the organs and tissues of the body until after the death of the animal1 and the packing-house practice of rapidly eviscerating the hogs immediately after slaughter would certainly preclude this possibility4 ,,possible ,,infection ,,from ,,pickling ,,fluids4 ,with regard to the second possibility1 that the bacillus finds its way into the hams in the curing pickles1 it was determined by laboratory experiment that the addition of #c per cent of sodium chlorid or #c per cent of potassium nitrate to laboratory media completely inhibits the growth of the bacillus4 ,as the pickling solutions always contain considerably more than these percentages of sodium chlorid and potassium nitrate1 it would be impossible for the bacillus to multiply in the pickles4 ,additional laboratory experiments demonstrated1 however1 that the bacillus or its spores may remain alive in the curing pickles for at least thirty days1 and it seemed possible that the curing pickles might become contaminated at times with the bacilli1 and that the bacilli1 although incapable of multiplying in the pickles1 might find their way into the bodies of the hams in the pickling fluids4 ,in order to throw some light upon this point1 the following experiment was carried out3 ,,experiment ,,to ,,show ,,whether ,,infection ,,takes ,,place ,,from ,,the ,,curing ,,pickle4 ,in this experiment two tierces were put down1 each containing #bj hams4 ,the hams weighed from #ad to #af pounds and had received the usual #dh-;hour chilling4 ,the pickling solutions employed were the regular curing pickles of the establishment at which the experiment was carried out4 ,the curing pickle in one tierce was inoculated with #djj cubic centimeters of a culture suspension of the bacillus1 prepared in the same manner as that used for the injection of the hams in tierce #b in ,experiment ,,ii4 ,a microscopic preparation made from a small drop of the culture suspension before adding it to the pickle showed the bacilli in large numbers1 and in the #djj cubic centimeters of the suspension there were millions of the bacteria4 ,the curing pickle in the other tierce was left untreated1 the hams in this tierce serving as a check4 ,the tierces used in this experiment1 as in all of the experiments1 were thoroughly cleaned with boiling water before the hams were placed in them4 ,the experiment was conducted in a pickling room which was held at #cc to #cf ,f41 and the tierces were rolled three times during the cure4 ,the details of the experiment are as follows3 ,tierce #a4--;,contained #bj hams1 half of which were pumped in both body and shank and half in the shank only4 ,as soon as they were pumped the hams were packed in the tierce4 ,sufficient curing pickle to fill the tierce was then measured out in a clean barrel and to it was added the culture suspension4 ,the culture was thoroughly mixed with the pickle and the latter was then run into the tierce containing the hams4 ,result3 ,when tested at the end of the cure1 two of the hams which had been pumped in the shank only showed slight souring in the body4 ,the rest of the hams were sweet4 ,tierce #b4--;,contained #bj hams which were pumped in the same manner as those in tierce #a4 ,the curing pickle was the same as that used for tierce #a1 but without the addition of culture4 ,this tierce was put down as a check on tierce #a1 the hams being cured under exactly the same conditions1 but without the addition of culture to the curing pickle4 ,result3 ,one of the hams which was pumped in the shank only developed slight souring in the body4 ,the remainder of the hams were sweet4 ,comparing tierce #a1 which contained the inoculated pickle1 with tierce #b1 the check tierce which contained uninoculated pickle1 we find there was practically no difference in the final result4 ,in tierce #a two of the hams developed slight souring1 while in tierce #b one of the hams became slightly sour4 ,all of these hams had been pumped in the shank only4 ,the fact that one of the hams in the check tierce developed slight souring was undoubtedly due to bacterial contamination in pumping or in the handling which the hams underwent prior to pickling1 and the slight souring of the two hams in tierce #a must also be attributed to the same cause or causes1 for had the souring in these last hams resulted from the penetration of the bacteria from the pickling solution a higher percentage should have become sour4 ,furthermore1 if the souring of the two hams in tierce #a had resulted from the penetration of the bacteria from the curing pickle1 the souring should have been general throughout the bodies of these hams1 whereas the souring was only evident around the bone and was slight in degree4 ,from this experiment the conclusion would seem justified that the bacillus which causes ham souring does not usually find its way into the bodies of the hams from the curing pickle1 although it would be going too far1 perhaps1 to say that infection never takes place from the curing pickle4 ,the experiment1 however1 indicates clearly that the curing pickles are certainly not the main channel through which the hams become infected4 ,in referring to the curing pickles1 it should be understood that we refer here to the pickling solutions in which the hams are immersed1 and not to the pumping pickles4 ,the possibility of infection through the pumping pickle will be discussed later4 ,,possible ,,infection ,,through ,,manipulation ,,or ,,handling4 ,there are at least three possible ways in which hams may become infected from the handling which they receive in preparation for1 or during the process of curing1 viz3 ,from the thermometers used in taking the inside temperatures of the hams1 from the pumping needles1 and from the billhooks used in lifting the hams4 ,,infection ,,from ,,ham ,,thermometers4 ,the packing-house method of taking the temperatures of hams by means of a pointed1 metal-capped thermometer which is thrust deep into the bodies of the hams has already been referred to1 but deserves to be described somewhat more in detail1 as it will be at once apparent that this manipulation furnishes a ready means whereby hams may become infected with putrefactive bacteria4 ,the construction of a ham thermometer is shown in figure #d4 ,illustration3 ,a4 ,b4 ,,fig4 #d4--;,diagrammatic views showing construction of ham thermometer4 ,a1 front view1 showing open space between metal point and mercury bulb1 which becomes filled with particles of meat1 grease1 and dirt2 ,b1 side view4 ,the instrument consists of a glass thermometer inclosed in a metal case1 the front portions of the case being cut away so as to expose the scale above and the mercury bulb below4 ,as was explained before1 the thermometer is thrust deep into the body of the ham so that the pointed end containing the mercury bulb rests beside or a little behind the upper portion of the femur1 the bone being used as a guide in introducing the thermometer4 ,ham temperatures are taken at three stages in the preparation for cure--7#a7 on the hanging floor1 just before the hams go to the chill rooms1 in order to determine the amount of heat lost prior to chilling2 7#b7 on leaving the chill rooms1 in order to determine the thoroughness of the chill2 7#c7 on the packing floor1 just before the hams are placed in pickle1 as a further check on the thoroughness of the chilling4 ,in taking the temperatures of hams which have been chilled--and most of the temperatures are taken subsequent to chilling--it is customary for the packing-house attendant who has this matter in charge to warm the thermometer by holding the pointed or bulb end in his hand1 so as to force the mercury column up to about #fj ,f41 or well above the temperature of hams4 ,the thermometer is then thrust into the ham and allowed to remain for several minutes1 by which time the mercury column will have fallen to the temperature of the ham4 ,the thermometer is then slowly withdrawn so as to expose the top of the mercury column1 and an accurate reading is thus obtained of the inside temperature of the ham4 ,the thermometer is warmed by the hand before each ham is tested1 and this undoubtedly insures more accurate readings than would result were the thermometer removed from one ham and plunged immediately into another1 but the procedure is open to certain objections1 for the open space between the metal point of the thermometer and the mercury bulb soon becomes filled with particles of meat and with grease and dirt from the attendant's hands1 and it is at once apparent that a thermometer in this condition would furnish a ready means whereby extraneous matter might be introduced into the bodies of the hams4 ,in other words1 a contaminated thermometer would furnish an excellent means whereby hams could be inoculated with putrefactive bacteria4 ,in order to determine whether hams actually become inoculated in this manner1 the following experiment was carried out3 ,,experiment ,,to ,,show ,,whether ,,hams ,,become ,,infected ,,from ,,ham ,,thermometers4 ,this experiment was designed to show 7#a7 whether the usual packing-house method of taking ham temperatures was apt to induce souring in the hams thus tested1 and 7#b7 whether souring would result in hams which were tested with a thermometer purposely contaminated with the bacillus isolated from sour hams4 ,the experiment was carried out as follows3 ,thirty hog carcasses were selected as they entered the hanging floor from the killing floor4 ,they had been cleaned1 eviscerated1 and split1 and were of the same average weight and of sufficient size to yield hams weighing from #ab to #ad pounds4 ,they were divided into three lots of #aj each and were allowed to remain on the hanging floor for two hours1 after which they were given the usual #dh-;hour chilling4 ,lot #a4--,the hams in this lot were tested with an ordinary ham thermometer as they entered the hanging floor1 as they left the hanging floor1 and as they left the coolers4 ,the thermometer used was borrowed from one of the plant attendants and was used in the condition in which it was received from him2 that is1 it was not cleaned or disinfected prior to use4 ,lot #b4--,the hams in this lot were tested as they entered the hanging floor with a thermometer which had been previously cleaned and disinfected and then dipped in a culture suspension of the meat-souring bacillus which was isolated from sour hams4 ,the thermometer was dipped in the culture suspension before each ham was tested4 ,no further temperatures were taken of these hams4 ,the thermometer was carefully cleaned and disinfected before it was returned to the attendant from whom it was borrowed4 ,lot #c4--,the hams in this lot were not tested at all1 and were intended as checks on the cure4 ,the three lots of carcasses were carefully tagged and were chilled in a special cooler to themselves4 ,upon leaving the cooler the hams were cut from the carcasses and trimmed4 ,the three lots of hams were then cured in separate tierces4 ,all of the hams were subjected to exactly the same cure4 ,the pickles used were the regular pumping and regular curing pickles of the establishment at which the experiment was carried out4 ,the hams in lot #c were pumped first and those in lot #a were pumped next4 ,the needle was then removed and a fresh1 clean needle was used for lot #b4 ,this was done in order to prevent the possibility of carrying over bacteria from one lot of hams to another on the pumping needle4 ,the tierces were thoroughly cleaned with boiling water before being used4 ,the curing was carried out in a pickling cellar which was held at #cc to #cf ,f41 the temperature never rising above the latter figure4 ,the tierces were rolled three times during the curing4 ,the details and results were as follows3 ,tierce #a4--;,contained #bj hams1 half of which were pumped in both body and shank and half in the shank only4 ,these hams were taken from the carcasses in lot #a and had been tested several times with a ham thermometer1 as already described4 ,result3 ,at the end of the cure it was found that of the #aj hams which were pumped in the shank1 #e showed well-marked souring in the body1 while of the #aj hams which were pumped in both body and shank1 #b showed slight souring in the body4 ,tierce #b4--;,contained #bj hams1 which were pumped in the same manner as those in tierce #a4 ,these hams were taken from the carcasses in lot #b and had been tested once with a thermometer which was dipped in a culture suspension of the bacillus isolated from sour hams4 ,result3 ,the #aj hams which were pumped in the shank only all became sour4 ,when they were tried out at the end of the cure1 they showed pronounced souring throughout the entire body and were classed as 8stinkers0 by the meat inspector who examined them4 ,the souring extended through to the bone marrow of the femur in all of these hams4 ,of the #aj hams which were pumped in both body and shank1 #g showed well-marked souring in the body1 but not as pronounced as in those pumped in the shank only2 in five of these hams the souring extended through to the bone marrow of the femur1 while in #b the bone marrow remained sweet4 ,tierce #c4--;,contained #bj hams1 which were pumped in the same manner as those in the two preceding tierces4 ,these hams were not tested with a thermometer1 and were put down as a check on the cure4 ,they were pumped with the same pumping pickle1 subjected to the same cure1 and held under precisely the same conditions as the hams in the two preceding tierces4 ,result3 ,when tested at the end of the cure1 all of these hams were found to be perfectly sound and sweet4 ,results of experiment to show whether hams become infected from ham thermometers4 ,no4 of ,number ,average ,how pumped4 tierce4 of weight of hams4 hams4 ,pounds4 #aj in shank #a #bj #ab-ad #aj in body and shank #aj in shank #b #bj #ab-ad #aj in body and shank #aj in shank #c #bj #ab-ad #aj in body and shank ,condition at end of cure4 ,no4 of tierce4 ,treatment4 ,number ,percentage of sour of sour hams4 hams4 ,tested at several #e #ej stages in #a preparation for cure with ham thermometer which had not been cleaned4 do #b #bj ,tested once with #aj #ajj #b ham thermometer dipped in culture suspension of anaerobic bacillus isolated from sour hams4 do #g #gj #c ,not tested with #j #j thermometer4 do #j #j ,several hams from each tierce were examined bacteriologically4 cultures being taken from the meat near the bone and from the bone marrow of the femur4 ,in the sour hams from tierce #a cultures taken from the meat near the bone showed the same anaerobic bacillus noted in other sour hams 7i4e41 the same bacillus which caused souring in ,experiments ,i and ,,ii71 but these cultures were contaminated with other bacteria which were probably introduced on the thermometer along with the ham-souring bacillus4 ,none of the contaminating bacteria were capable1 however1 of producing a sour-meat odor when grown on the egg-pork medium4 ,pure cultures of the ham-souring bacillus were obtained from the bone marrow of some of these hams1 showing that this bacillus had penetrated through to the bone marrow while the other bacteria had not4 ,from the sour hams in tierce #b the ham-souring bacillus was recovered readily1 and often in pure culture1 from the hams which had been pumped in the shank only1 whereas it was usually contaminated with pickle bacteria in the hams which had been pumped in both body and shank4 ,in the case of the sound hams in tierce #c1 cultures taken from the meat near the bone and from the bone marrow of the femur were negative in the hams which had been pumped in the shank only1 while cultures taken from corresponding points in the hams pumped in both body and shank showed ordinary pickle bacteria1 which had evidently been introduced into the bodies of these hams in the pumping pickles4 ,none of these hams exhibited the slightest sour odor4 ,summary of experiment4--,in this experiment #bj hams 7tierce #a7 were tested with an ordinary ham thermometer in the usual packing-house manner4 ,half of these hams were subjected to the mild cure and half were given the regular cure1 with the result that #ej per cent of those receiving the mild cure and #bj per cent of those receiving the regular cure became sour4 ,a second lot of #bj hams 7tierce #b7 were tested with a thermometer which had been purposely contaminated with a culture suspension of the ham-souring bacillus4 ,these hams were cured in the same manner as the first lot1 with the result that all of those receiving the mild cure and #gj per cent of those receiving the regular cure became sour4 ,a third lot of #bj hams 7tierce #c7 which had not been tested at all were cured in the same manner as the two preceding lots1 as a check on the cure4 ,all of these hams were sweet at the end of the cure4 ,inasmuch as the three lots of hams were cured under precisely the same conditions and were handled in the same manner prior to pickling1 the only difference being that the hams in tierces #a and #b were tested with the ham thermometer while those in tierce #c were not1 we must conclude that the souring of the hams in tierces #a and #b resulted from the testing which these hams received4 ,in the case of tierce #a the hams became infected from a thermometer which1 in the ordinary routine use of the packing house1 had become accidentally contaminated with the ham-souring bacillus4 ,in the case of tierce #b the hams became infected from a thermometer which had been artificially contaminated with the bacillus4 ,the high percentage of sours in this last lot is due to the fact that these hams were heavily infected with the ham-souring bacillus1 for owing to the construction of the ham thermometer many thousands of the bacilli were unquestionably introduced into each ham on the point of the thermometer4 ,in the ordinary routine of ham testing1 where hams become infected from foreign matter introduced on the thermometer1 the percentage of souring1 as shown in tierce #a1 would be less1 for it is not to be supposed that ham thermometers are always contaminated with the ham-souring bacillus1 but that they only become so at times1 and that probably only a few of the bacilli are then introduced4 ,this experiment1 we think1 proves conclusively 7#a7 that the ham-souring bacillus may be introduced into the bodies of hams on the thermometers used in testing the hams1 and 7#b7 that the packing-house method of taking ham temperatures by means of a thermometer which is thrust deep into the bodies of the hams may cause souring in the hams thus tested4 ,as a further proof that hams may become contaminated in this manner1 a series of cultures were made from scrapings taken from ham thermometers4 ,the scrapings consisted of the accumulations of bits of meat1 grease1 and dirt that collect on the thermometers1 and were taken from the thermometers while the latter were in ordinary routine use in the packing house4 ,in a series of six cultures which were made from such scrapings at different times1 the same bacillus which was isolated from sour hams and shown to cause meat souring was found three times4 ,in other words1 the ham-souring bacillus was present in #ej per cent of the cultures made from thermometer scrapings1 and many hams undoubtedly become infected from the thermometers4 ,souring would be almost certain to result in mild-cure hams if these hams were tested with a thermometer which had become accidentally contaminated with the ham-souring bacillus1 as the bacillus would have time to develop within the bodies of the hams before being inhibited by the curing pickle1 which penetrates slowly into the bodies of these hams4 ,in the case of regular cure hams--that is1 hams which are pumped in both body and shank--souring would be much less apt to occur after the use of a contaminated thermometer1 as these hams are more or less saturated with a strong pumping pickle at the beginning of the cure1 which would tend to inhibit the growth of any bacteria that might be introduced on the thermometers4 ,the fact that souring may result in hams from the use of a contaminated thermometer would explain the occurrence of several sours in one vat1 for in testing hams just before they go into cure several hams are usually tested in succession1 and these would in all likelihood go into the same vat4 ,supposing the thermometer to have been contaminated with the ham-souring bacillus at the time these hams were tested1 this would explain a fact which has been often noted1 namely1 the occurrence of several sours in one vat while other vats containing the same run of hams show no sours4 ,if souring resulted in all of the hams which are subjected to a thermometer test in the daily routine of the packing house1 this manipulation alone might account for nearly all of the sours which occur1 but the experiment which has been just described shows that all of these hams do not become sour4 ,in tierce #a1 where each ham was subjected to three thermometer tests at different times1 souring resulted in #ce percent 7this includes both mild and regular cure7 of the hams thus tested1 and in actual practice the percentage of sours in hams which have been subjected to the thermometer test would probably be somewhat less4 ,quite a large percentage of sour hams are thus left unaccounted for by the thermometer test1 and we believe that these are chiefly the result of contamination carried in on the pumping needles or in the pumping pickles4 ,,infection ,,from ,,pumping ,,needles4 ,in view of the results obtained in the last experiment1 in which it was shown that hams may become infected from the use of ham thermometers1 it seemed not improbable that hams might also become infected from the pumping needles1 which1 like the thermometers1 are thrust deep into the bodies of the hams beside the bone4 ,in order to throw some light upon this point1 cultures were taken from the grease and dirt that accumulate on the shields at the bases of the pumping needles1 as such material must undoubtedly be carried into the hams at times on the needles4 ,the ham-souring bacillus was found several times in these cultures1 and hence it is fair to infer that hams may also become infected at times from the pumping needles1 just as they become infected from the thermometers4 ,bits of contaminated meat and grease and particles of dirt carried in on the pumping needles would be forced out into the hams by the pumping pickle1 which passes out through small openings or fenestr in the needles1 and this probably affords one explanation as to why so many more body sours occur in the mild-cure hams4 ,in the mild-cure hams1 which are pumped in the shank only1 the pumping needle is introduced near the femorotibial articulation1 and the shank is saturated at the start with a strong brine solution1 while the body of the ham is not4 ,if the ham-souring bacillus were carried into these hams on the pumping needle1 the growth of the bacillus in the shank would be inhibited by the strong brine solution with which the shank is saturated1 but there would be nothing to prevent the bacillus from growing upward into the body of the ham1 which has not been pumped and is free from pickle4 ,this would also explain the fact that the souring often starts at the knee joint and extends upward into the body of the ham4 ,in the case of the regular cure hams1 where the ham is pumped in both body and shank1 the entire ham is more or less saturated at the start with the strong brine of the pumping pickle1 which tends to inhibit the growth of the ham-souring bacillus even if this bacillus should find its way into these hams on the pumping needles4 ,it is in the mild-cure or partly pumped hams1 where the body of the ham is left unpumped1 that the ham-souring bacillus finds its best opportunity for development1 and the greater proportion of the sours that occur in the packing house are found in these hams4 ,as regards the possibility of infection from the pumping pickle itself1 it does not seem probable that this would often occur1 for the pumping and curing pickles are always prepared on an upper floor of the pickling houses and are delivered to the pickle cellars in closed pipes1 so the chances for the accidental contamination of these solutions from floating dust or dirt would not be great4 ,furthermore1 the strong brine of the pumping pickle would completely inhibit the growth of the ham-souring bacillus1 and the bacillus would be incapable of multiplying1 even if it found its way into the pickle4 ,on the other hand1 laboratory experiments show that the bacillus or its spores may remain alive for a considerable length of time in the pumping pickle1 so the possibility of infection from this source can not be overlooked4 ,,infection ,,from ,,billhooks4 ,after the hams are cut from the carcasses they are handled entirely by means of billhooks4 ,in handling the hams the hooks are inserted beneath the skin of the shank at a point just above the tibio-femoral articulation4 ,the hooks should be inserted in the connective tissue beneath the skin and should not penetrate the muscular tissue to any depth4 ,when the hams lie in the right position1 with the butt or large portion away from and the shank toward the operator1 it is an easy matter to pick them up in the proper manner2 but when they lie at different angles and are being rapidly handled it is almost impossible to prevent the hook from penetrating the muscular tissues1 and if the hook should penetrate to the bone it might carry in foreign matter contaminated with the meat-souring bacillus4 ,it is not probable that many hams become contaminated in this way1 as the men who handle the hams are very skillful in manipulating their hooks2 but the possibility that hams may become contaminated in this manner should not be entirely overlooked4 ,,biological ,,and ,,morphological ,,characteristics ,,of ,,the ,,ham-,,souring ,,bacillus4 ,,conditions ,,favorable ,,to ,,growth4 ,the most favorable medium for the growth of the organism was found to be the modified egg-meat mixture of ,rettger1 which has been previously described4 ,in this medium the organism develops rapidly at a temperature of #bj to #be ,c41 giving rise to the characteristic sour-meat odor4 ,like the bacillus described by ,klein1 it also grows readily on pork-agar and pork-bouillon containing glucose1 but differs from ,klein's bacillus in that it will grow1 though less luxuriantly1 on ordinary nutrient media--agar1 gelatin1 and bouillon--without the addition of glucose4 ,the optimum temperature for growth is #bj to #be ,c4 ,the organism does not grow at incubator temperature 7#cg4e ,c474 ,at ice-box temperature 7#h to #aj ,c47 it develops readily1 although the growth is less rapid than at #bj to #be ,c4 ,that the organism will develop at even lower temperatures was shown in the inoculation experiments with hams1 where it developed and multiplied extensively in the bodies of the hams at the temperature of the pickling cellars1 which are held usually at #cd to #cf ,f4 7#a to #b ,c474 ,the organism develops best in a neutral or slightly alkaline medium4 ,,growth ,,on ,,different ,,culture ,,media4 ,growth on egg-pork medium4--,at a temperature of #bj to #be ,c4 the cultures show a slight but distinct sour odor in from two to three days4 ,this odor1 as before stated1 closely resembles the odor of a sour ham4 ,egg-pork cultures from three to five days old were given to a trained meat inspector1 who knew nothing whatever as to the contents of the tubes1 and he was asked to describe the odor2 he described it as that of a sour ham4 ,at one week the albumins of the medium are gelatinized or partly coagulated and the odor is more pronounced4 ,at ten days the albumins are completely coagulated except at the surface1 where there is no apparent growth2 the odor is more putrefactive in nature1 and the reaction of the medium is slightly acid4 ,at three weeks the coagulated albumin splits up into fragments and appears to undergo a slow digestion1 gas bubbles form in the lower portion of the culture1 and the odor becomes distinctly putrefactive in character4 ,the slow digestion of the albumin is probably due to a proteolytic enzyme elaborated by the bacillus4 ,at the end of a week a dark zone usually appears at the surface of the coagulated albumin and gradually darkens until it becomes almost black4 ,this zone is probably due to a pigment elaborated by the bacillus4 ,at ice-box temperature 7#h to #aj ,c47 the same changes and the same odor were noted1 but were somewhat slower in developing4 ,glucose-pork-agar4--,this medium was prepared from pork in the same manner as beef-agar1 and contained #a per cent of glucose4 ,the organism grows readily on this medium and may be conveniently cultivated in deep stab cultures4 ,the medium was always thoroughly boiled and then rapidly cooled in order to expel the inclosed air4 ,the growth of the organism was found to vary considerably with the reaction4 ,when the reaction was #a4e1 deep stab cultures at three days 7#bj to #be ,c47 showed a well-marked arborescent growth1 appearing as delicate filaments extending outward from the line of stab4 ,the growth stopped within one-fourth or one-half inch of the surface of the agar on account of the presence of oxygen in the upper part of the culture medium4 ,as the growth extended toward the walls of the test tube the agar became clouded1 and there were sometimes gas bubbles in the depth of the agar1 but the gas formation was not extensive4 ,when the reaction of the agar is neutral or slightly alkaline1 extensive gas formation occurs and the agar is often much broken up4 ,the cultures developed a disagreeable1 somewhat putrefactive odor1 but did not give the characteristic sour-ham odor obtained from the egg-pork cultures4 ,the organism was also grown on anaerobic agar plates by ,zinsser's method1 which is said to give absolutely anaerobic conditions4 ,the colonies on agar have a cottony or woolly appearance at first1 and spread slowly1 with slightly irregular margins4 ,in glucose-pork-agar to which azolitmin was added the azolitmin in the lower portion of deep stab cultures was completely decolorized in five days at room temperature 7#bj to #be ,c74 ,in glucose-pork-agar containing neutral red the red color in the lower portion of the tube was changed to yellow with the development of fluorescence4 ,neutral gelatin4--,tubes of ordinary neutral gelatin without the addition of glucose were inoculated and held at ice-box temperature 7#h to #aj ,c74 ,at five days a delicate white growth appeared along the line of stab in the lower portion of the tube4 ,at seven days the growth showed fine radial stri1 presenting an arborescent or tree-like appearance1 and extended halfway from the line of stab to the walls of the test tube4 ,at two weeks the growth had caused a delicate clouding of the medium in the lower portion of the tube4 ,at three weeks the gelatin in the lower portion of the tube had become liquefied and the growth had settled to the bottom as a white precipitate4 ,in gelatin containing glucose1 gas bubbles are formed in the depth of the medium through the splitting up of the glucose1 and the characteristic arborescent growth is obscured4 ,glucose-pork-bouillon4--,this medium was prepared from pork instead of beef and contained #a per cent of glucose4 ,the best results were obtained when the reaction of the medium was neutral or slightly alkaline4 ,culture tubes1 which had been previously boiled to expel the contained air and then inoculated1 were held in a ,novy jar1 in an atmosphere of hydrogen at a temperature of #bj to #be ,c4 ,at three days the tubes showed well-marked clouding4 ,at one week the growth appeared as a heavy1 white1 flocculent1 cottony precipitate in the bottom of the tubes with a slight flocculent precipitate above4 ,when the culture was removed from the jar and shaken1 the heavy1 flocculent precipitate at the bottom of the tube broke up without much difficulty1 giving rise to a heavy uniform clouding with some small floating masses1 which soon settled to the bottom4 ,on shaking the tube some evolution of gas in the form of very fine bubbles was noticed4 ,in ,smith fermentation tubes containing neutral glucose-pork-bouillon the closed arm of the tube shows well-marked clouding with gas formation at three days at room temperature 7#bj to #be ,c74 ,the growth has a tufted1 cottony appearance1 and there are many filaments and threads4 ,the growth settles to the bottom of the closed arm as a cottony1 white precipitate 7see ,pl4 ,,iv74 ,the organism splits the glucose vigorously1 and at #aj days the tubes show from #dj to #ej per cent of gas4 ,the bouillon in the open arm of the tube remains unclouded4 ,the maximum gas production at room temperature is reached in from #aj to #ad days1 by which time the growth in the closed arm has completely settled into the bend of the tube1 leaving the bouillon in the closed arm clear4 ,the gas formula1 as determined by ,smith's method1 was ,h_/,,co #e_/a4 ,the reaction of the bouillon becomes acid to phenolphthalein4 ,the organism will grow on ordinary neutral bouillon without the addition of glucose1 and in ,smith tubes containing this medium a small amount of gas was formed1 due to the splitting of the muscle sugar4 ,the bacillus also grows in a sugar-free broth--that is1 a broth free from muscle sugar--and from cultures grown in this medium a well-marked indol test was obtained4 ,litmus-milk4--,the organism was grown in litmus-milk in ,smith fermentation tubes at #bj to #be ,c4 ,at seven days the litmus in the lower portion of the closed arm had assumed a brownish-buff color4 ,at two weeks the litmus in the closed arm had been reduced to a brownish-buff color except at the top of the tube1 where a pale1 bluish tinge remained1 and the litmus in the open arm showed very slight reddening as compared with a check tube4 ,at three weeks the litmus in the closed arm was entirely reduced to a light1 brownish-buff color1 and the litmus in the open arm showed a slight but distinct reddening as compared with the check4 ,the reddening of the litmus in the open arm was evidently due to the transfusion of acids formed by the growth of the bacillus in the closed arm4 ,after several weeks the milk is slowly peptonized1 probably as a result of enzyme action4 ,,morphology4 ,the organism is a large bacillus having an average size of #d to #h in length by #j4e to #j4g in thickness1 but there are many longer forms measuring from #aj to #bj in length4 ,it develops in long1 irregular chains or filaments1 which at times show a slightly spiral form4 ,illustration3 ,,fig4 #e4--;,ham-souring bacillus 7,bacillus putrefaciens7 grown on egg-pork medium1 showing tendency to form chains4 ,partly developed and fully developed spores are shown at ends of rods2 also free spores4 7,pen-and-ink drawing made with camera lucida from preparation stained by ,gram's method4 #fdj47 ,the individual organisms show at times a widely open1 slightly spiral form1 which was more apparent in hanging-drop preparations made from bouillon cultures1 where the organisms had been comparatively undisturbed4 ,this appearance was also noted at times in the stained sections of soured muscular tissue1 where the organisms were stained in place4 ,the organism possesses no motility4 ,it stains with the ordinary aniline dyes and by ,gram's method4 ,,spore ,,formation4 ,the organism develops large1 terminal spores1 which are at first oval1 but when fully developed are perfectly round and measure from #a4e to #b in diameter4 ,spores develop rapidly in the egg-pork medium at #bj to #be ,c41 fully developed spores being noted in from five to seven days4 ,at ice-box temperature 7#h to #aj ,c47 partly developed spores were noted in the egg-pork medium at #aj days and fully developed spores at #b weeks4 ,occasional spores were noted in old agar and gelatin cultures1 but abundant spore formation was seen only in the egg-pork medium4 ,no spores were noted in bouillon cultures1 even at #aj weeks4 ,,resistance ,,to ,,heat ,,and ,,chemical ,,agents4 ,in its vegetative form the bacillus is killed at #ee ,c4 in #aj minutes4 ,the spores survive a temperature of #hj ,c4 for #bj minutes1 but are killed at #ajj ,c4 in #aj minutes4 ,when sodium chlorid and potassium nitrate were added to glucose-pork broth in varying amounts1 it was found that #c per cent of sodium chlorid or #c per cent of potassium nitrate was sufficient to inhibit completely the growth of the bacillus at room temperature 7#bj to #be ,c474 ,while the growth of the bacillus was inhibited by sodium chlorid and potassium nitrate as just stated1 it was found that very much stronger solutions of the two salts failed to destroy the bacillus4 ,thus it was found that the bacillus or its spores retained their vitality after an exposure of #cj days in a solution containing #bc per cent of sodium chlorid and #f per cent of potassium nitrate4 ,,gas ,,production4 ,the organism splits glucose1 but not lactose or saccharose4 ,that it possesses the power of splitting muscle sugar was shown by the formation of gas in ,smith fermentation tubes containing ordinary neutral bouillon without the addition of any sugar4 ,the formation of gas in glucose bouillon varies considerably with the reaction of the medium4 ,the largest amount of gas was formed when the broth was neutral or slightly alkaline4 ,when the reaction of the broth was distinctly acid or distinctly alkaline the amount of gas was diminished4 ,the gas which is formed in bouillon cultures consists chiefly of hydrogen and carbon dioxide4 ,in order to collect a sufficient amount of the gas for analysis1 two large fermentation tubes capable of holding #aej cubic centimeters each were constructed4 ,these tubes were filled with pork-bouillon and inoculated with the bacillus4 ,after #bj days at room temperature 7#bj to #be ,c47 the gas was collected and the carbon dioxide and hydrogen determined1 with the following result3 ,cubic centimeters4 ,total amount of gas collected #cg4g ,carbon dioxide1 by absorption with ,na,o,h #f4b ,hydrogen1 by difference #ca4e ,this analysis gives an approximate gas formula of ,h_/,,co #e_/a1 which agrees with the gas formula as determined in the small fermentation tubes by ,smith's method4 ,in hams which had undergone spontaneous souring and in hams which had been artificially soured by inoculation1 hydrogen-sulphid was often noted when the sour portions of the meat were tested with lead-acetate paper1 but no distinct odor of the gas could be obtained4 ,hydrogen sulphid was also noted in egg-pork cultures of the bacillus4 ,,acid ,,production4 ,in glucose-bouillon1 butyric and lactic acids are formed and the reaction of the medium becomes distinctly acid4 ,butyric and lactic acids were also noted in the egg-pork cultures4 ,a series of ,smith fermentation tubes containing #aj c4 c4 each of glucose-pork broth medium was inoculated with the bacillus and held at room temperature 7#bj to #be ,c474 ,these cultures were titrated against ,n_/#dj,na,o,h1 with phenolphthalein as an indicator at intervals of two days up to nineteen days1 and then at two-week intervals up to sixty-one days4 ,three of the cultures were titrated each time so as to give a fair average of the acidity of the cultures1 and an uninoculated check tube was also titrated each time to see if there was any change in the reaction of the medium4 ,the results of the titrations are shown in the following table3 ,acidity determinations in glucose-pork broth cultures4 ,age of culture,culture,culture,culture,average4 ,medium4,acidity of 7days74 ,a4 ,b4 ,c4 culture4 ,per cent4 #b #j4jch #j4jcj #j4jdj #j4jcf #j4jji #j4jbg #d 4#aje 4#ajj 4#ajb 4#ajb 4#jji 4#jic #f 4#ajf 4#aaj 4#aji 4#ajh 4#jji 4#jii #h 4#abd 4#aae 4#aag 4#aai 4#jji 4#aaj #aj 4#abh 4#acj 4#abf 4#abh 4#jji 4#aai #ab 4#abi 4#abj 4#abi 4#abf 4#jji 4#aag #ai 4#abf 4#abe 4#abe 4#abe 4#jji 4#aaf #cc 4#abe 4#abc 4#abe 4#abd 4#jji 4#aae #dg 4#abb 4#abj 4#aba 4#aba 4#jji 4#aab #fa 4#aba 4#aaf 4#aai 4#aah 4#jji 4#aji ,from the above table it will be seen that the maximum acidity was reached at ten days1 after which there was a gradual reduction in the acidity1 due probably to the formation of ammonia compounds4 ,,pathogenic ,,properties4 ,rabbits1 guinea pigs1 and white mice were inoculated and fed with cultures of the bacillus without effect1 from which it would appear that the bacillus possesses no pathogenic or disease-producing properties4 ,,nature ,,of ,,the ,,bacillus4 ,the bacillus is essentially a saprogenic bacterium with zymogenic properties4 ,a preliminary study of the chemical changes which take place in sour hams shows that these changes are of a putrefactive nature4 ,hams which had undergone spontaneous souring were compared with hams which had been artificially soured by inoculation1 and the chemical changes were found to be identical4 ,a chemical study was also made of the changes taking place in egg-pork cultures of the bacillus at different stages of growth1 and these changes were found to be of a putrefactive nature and similar in character to the changes which occur in sour hams4 ,among the putrefactive products formed by the growth of the bacillus in the egg-pork medium were indol1 skatol1 volatile fatty acids1 skatol-carbonic acid1 and hydrogen sulphid4#d #d ,the tests for the putrefactive products formed by the growth of the bacillus in the egg-pork medium were made by ,p4 ,castleman1 of the ,biochemic ,division1 who also determined the percentage composition of the gas formed by the growth of the bacillus in the glucose-pork-bouillon medium4 ,illustration3 ,,bul4 #acb1 ,,bureau ,,of ,,animal ,,industry1 ,u4 ,s4 ,,dept4 ,,of ,,agriculture4 ,,plate ,,iv4 ,,glucose ,,bouillon ,,culture ,,in ,,smith ,,fermentation ,,tube ,,at ,,four ,,days4 ,,culture ,,grown ,,at ,,room ,,temperature 7#bj ,,to #be ,c474 ,,growth ,,confined ,,entirely ,,to ,,closed ,,arm1 ,,with ,,gas ,,collecting ,,at ,,top4 ,a more extended study is now being carried on in the ,biochemic ,division of the chemical changes which take place in hams during the process of souring1 together with a further study of the chemical changes which result from the growth of the bacillus in the egg-pork medium4 ,the results of this investigation will be given in a later paper4 ,the bacillus described in this paper belongs to the class of putrefactive anaerobes1 which are widely distributed in nature in dust1 soil1 and excrementitious matters4 ,this group of bacteria contains both pathogenic and nonpathogenic forms4 ,the former have received considerable attention1 but the latter have never been thoroughly cleared up4 ,the bacillus isolated from sour hams belongs in the latter category1 being possessed of no pathogenic or disease-producing properties4 ,it occurs in the dust and dirt of the packing house and finds its way into the hams in the various manipulations to which the hams are subjected4 ,the bacillus described in this paper does not seem to correspond with any forms heretofore described4 ,it differs from ,klei bacillus 7,bacillus fdans7 in the following important particulars3 7#a7 ,it forms large terminal spores1 whereas ,klein's bacillus formed no spores2 7#b7 it will grow at a temperature of #cd ,f41 while ,klei bacillus did not grow below #ej ,f42 7#c7 it produces an acid reaction in culture media1 while ,klei bacillus gave a distinctly alkaline reaction2 7#d7 it will grow on the ordinary nutrient media--gelatin1 agar1 and broth--without the addition of glucose1 while ,klein's bacillus did not2 7#e7 it peptonizes the casein in milk1 whereas ,klein's bacillus had no action on milk2 7#f7 it liquefies gelatin more rapidly1 causing complete liquefaction after three weeks at #h to #aj ,c41 whereas ,klein's bacillus caused only partial liquefaction after eight weeks at #bj ,c42 7#g7 it can be conveyed from turbid broth cultures to new culture material by means of the platinum loop1 whereas ,klein's bacillus could not be thus conveyed4 ,for the bacillus described in the present paper the following name is proposed3 ,bacillus putrefaciens4 ,,prevention ,,of ,,ham ,,souring4 ,as it has been shown that souring in hams results from the growth of a bacterium which is introduced into the bodies of the hams in the various manipulations which the hams undergo1 the only way to eliminate souring in hams1 as they are cured in the larger packing establishments1 would be to cure the hams under aseptic or sterile conditions1 which would1 of course1 be a physical impossibility4 ,while it will probably be impossible1 therefore1 to eliminate souring entirely under the methods of ham curing which are at present employed in the larger packing establishments1 much can undoubtedly be done toward reducing the percentage of sours4 ,in the matter of taking ham temperatures1 for instance1 if the thermometers used were thoroughly cleaned and disinfected and the surfaces of the hams seared at the point where the thermometer is introduced1 infection from this source could be entirely prevented2 or it might be possible so to regulate the temperature of the chill rooms that the taking of ham temperatures could be discontinued4 ,the elimination of the souring that results from the introduction of foreign matter on the pumping needles could be effected in two ways only1 7#a7 by not pumping the hams at all1 or 7#b7 by pumping them under sterile or aseptic conditions4 ,as has been stated before1 some of the smaller packing establishments cure their hams without pumping1 and in these establishments the percentage of sours runs very low4 ,when hams are cured without pumping1 however1 the period of curing has to be materially lengthened in order to give the curing pickles sufficient time to penetrate thoroughly1 and this is what the larger plants wish to avoid because of the greater space and greater number of vats which would be necessitated4 ,the object of pumping in the larger plants1 where the number of hams handled daily runs into the thousands1 is to hasten the cure and thus prevent the accumulation of a great number of hams at one time4 ,it is doubtful1 therefore1 whether the larger packing houses could conveniently discontinue pumping4 ,to pump the hams under aseptic conditions would necessitate a technique far too elaborate for routine use in the packing house2 in fact1 anything like complete asepsis would be out of the question4 ,certain measures might be adopted1 however1 that would tend to prevent the possible introduction of ham-souring bacilli in the process of pumping4 ,it would undoubtedly be safer1 for instance1 to boil the pumping pickle before use1 and the chances of carrying in contaminated foreign matter on the pumping needles could be lessened by sterilizing the pumps and needles with boiling water and by frequently dipping the needles1 while in use1 in boiling water4 ,if the hams were sprayed with clean water just prior to pumping1 there would be less likelihood of carrying in foreign matter on the needles4 ,the danger of introducing contaminated foreign matter on the needles might be further obviated by searing the surfaces of the hams at the points where the needles are introduced2 but such a procedure would be hardly practicable in the larger packing houses1 where the great number of hams cured necessitates rapid handling4 ,while the danger of possible contamination in pumping1 through the introduction of contaminated foreign matter on the pumping needles1 can not well be avoided1 this danger is partly counterbalanced by the inhibitory action of the pumping pickle1 which is strikingly shown in the experiments which have been described4 ,in these experiments1 #ajj hams received large doses of the ham-souring bacillus1 half of these hams being subjected to the mild cure and half to the regular cure1 with the following result3 ,in the case of the mild-cure hams1 which were pumped in the shank only1 the percentage of sours was practically #ajj per cent1 every ham with possibly one exception becoming sour2 whereas in the regular-cure hams1 which were pumped in both body and shank1 only #eh per cent of the hams became sour4 ,in other words1 the additional pumping which the regular-cure hams received served to prevent souring in #db per cent of these hams4 ,in these experiments the number of bacteria introduced into the hams was very great1 thousands and even millions of the bacilli being introduced into each ham1 whereas in the routine of the packing house it is not likely that more than a few of the bacilli are ever introduced at one time on the thermometers and pumping needles4 ,in view of these results it is safe to say that in the larger packing houses1 where pumping seems to be necessary1 the number of sours could be reduced fully #ej per cent if all hams were pumped in the body as well as in the shank4 ,at present the usual procedure is to pump all hams1 both mild and regular cure1 with the same pumping pickle1 the mild-cure hams being pumped in the shank only and the regular-cure hams at two additional points in the body4 ,the experiments quoted above show that the additional pumping which the regular-cure hams receive undoubtedly tends to prevent the development of souring in these hams1 and this result is unquestionably due to the inhibitory action of the salts contained in the pumping pickle1 as it was found by laboratory experiment that the addition of #c per cent of sodium chlorid to culture media is sufficient to inhibit the growth of the ham-souring bacillus4 ,the pumping pickles consist of strong brine solutions and always contain considerably more than #c per cent of sodium chlorid4 ,if1 therefore1 the pumping of regular-cure hams were made more thorough than at present1 and all of the deeper portions of the ham were thoroughly saturated with the strong brine solution1 souring could be largely eliminated1 if not entirely prevented1 in these hams1 as an unfavorable medium or soil would thus be created in which the ham-souring bacillus could not develop4 ,the ham-souring bacillus is able to develop within the bodies of the regular-cure hams because the pumping of these hams is not always thorough and there are certain areas in the inner or deeper portions of the hams in which the tissues are not thoroughly saturated with the pumping pickle4 ,under the present methods of curing1 the greater proportion of the sours occur among the partly pumped or mild-cure hams4 ,these hams are pumped in the shank only1 and the growth of the ham-souring bacillus within the bodies of these hams is not interfered with until the curing pickle has penetrated from the outside4 ,as it requires several weeks for the curing pickle to penetrate thoroughly into the deeper portions of these hams1 the bacillus is thus afforded a considerable interval in which to develop before it is exposed to the inhibitory action of the pickle4 ,if these hams could be thoroughly pumped in the body at the beginning of the cure in the same manner as the regular-cure hams1 the chief loss from ham souring would be eliminated4 ,it would not do1 however1 to pump these hams in the body with the same pumping pickle used in the regular cure1 as the meat would be rendered too salty and the mild flavor of the ham would be lost4 ,there is undoubtedly a demand for mild-cure hams1 otherwise they would not be on the market2 and the question then arises how to pump these hams and still retain a mild cure4 ,this might be accomplished by pumping these hams with their own curing pickle1 which is usually a milder pickle than that employed in the regular cure1 or an even milder pumping pickle might be used4 ,if mild-cure hams were pumped in this way1 the percentage of souring in these hams could undoubtedly be greatly diminished without materially affecting the flavor of the ham4 ,to recapitulate briefly1 the prevention of ham souring is to be sought in two ways3 7#a7 ,through greater care in handling the hams and the adoption of precautionary measures to prevent the introduction of the ham-souring bacillus into the bodies of the hams1 and 7#b7 through more thorough pumping of the deeper or inner portions of the hams1 so as to create an unfavorable soil or medium in which the ham-souring bacillus can not develop even if it should gain entrance into the bodies of the hams4 ,from what has been said it will be apparent that ham souring can probably never be entirely eliminated from the packing house under the present methods of curing1 but the adoption of precautionary measures in testing and pumping hams1 together with a more thorough pumping of all hams in ways similar to those suggested1 would unquestionably reduce very materially the losses from this source4 ,,general ,,summary ,,and ,,conclusions4 #a4 ,in this paper it has been shown that ham souring1 as encountered in the wet cure where the hams are entirely submerged in pickling fluids1 is due to the growth of an anaerobic bacillus within the bodies of the hams4 ,this bacillus 7,b4 putrefaciens7 was found in sour hams obtained from four different packing establishments4 ,it was isolated and grown in various laboratory media1 in one of which1 the egg-pork medium1 it gave rise to the characteristic sour-ham odor4 ,this bacillus was the only organism that could be isolated from sour hams that was capable of producing the characteristic sour-ham odor in the egg-pork medium4 #b4 ,when injected into the bodies of sound hams1 the bacillus caused these hams to sour in the process of curing4 ,in hams which had been inoculated with the bacillus and thus artificially soured1 the bacillus was recovered in cultures taken at points far removed1 relatively speaking1 from the point of inoculation1 indicating that the bacillus had multiplied and progressed by extension throughout the bodies of the hams4 #c4 ,the bacillus possesses no motility1 and its extension throughout the bodies of the hams is a result of multiplication4 ,in its growth it follows along the connective-tissue bands between the muscle bundles1 which are composed of comparatively loose tissue and afford paths of least resistance4 ,when it invades the muscle tissue proper1 it follows along the sarcolemma sheaths between the muscle fibers4 ,as a result of this growth the muscular tissue becomes softer and tends to break more easily4 #d4 ,the bacillus belongs to the class of putrefactive anaerobes which are widely distributed in nature in dust1 soil1 and excrementitious matters4 ,the bacillus or its spores is present in the dust and dirt of packing houses and finds its way into the hams in the various manipulations to which they are subjected4 #e4 ,the bacillus or its spores may be introduced into hams on the thermometers used in testing the hams1 on the pumping needles1 and possibly on the billhooks used in handling the hams4 ,it may also be carried into the hams in the pumping pickle1 and may even find its way into the hams from the curing pickle1 although infection through the latter channel probably does not often occur4 #f4 ,the bacillus develops in the deeper portions of the ham because of the anaerobic conditions there prevailing1 and souring is most often encountered1 therefore1 in the deeper portions of the ham near the bone4 #g4 ,a preliminary study of the chemical changes which take place in the process of souring shows that these changes are of a putrefactive nature1 and ham souring1 as ordinarily encountered1 is to be regarded as an incipient putrefaction4 ,hams which had been artificially soured by injections of culture were compared with sour hams obtained from the packing house1 and the putrefactive changes were found to be identical4 #h4 ,hams which have once become sour can never be restored to a sound condition1 because of the chemical changes which result from the growth of the bacillus4 ,in other words1 the tissues of the ham undergo certain chemical changes in the process of souring1 and when these changes have once taken place the tissues can never be restored to a sound condition4 ,the repumping of slightly soured hams with a strong pumping pickle will check further souring1 by inhibiting the growth of the bacillus1 but will not restore to a sound condition those portions of the ham which have become sour4 #i4 ,the salts of the pickling fluids have a marked inhibitory action on the ham-souring bacillus1 and sours occur less frequently in regular-cure hams4 #aj4 ,in regular-cure hams the growth of the ham-souring bacillus is restricted and often completely inhibited as a result of the additional pumping which these hams receive1 whereby they are more or less saturated with pickle at the beginning of the cure4 #aa4 ,if the pumping of regular-cure hams were more thorough and all of the deeper portions of the ham were thoroughly saturated with the pumping pickle1 souring could be largely eliminated if not entirely prevented in the hams1 as an unfavorable medium or soil would thus be created1 in which the ham-souring bacillus could not develop4 ,the reason that souring does develop in regular-cure hams is because the pumping is not always thorough and there are certain areas in the deeper portions of these hams which are not saturated with the pumping pickle4 #ab4 ,under the present methods of curing1 the partly pumped or mild-cure hams furnish the greater proportion of the sours1 as these hams are not pumped in the body and the growth of the ham-souring bacillus within the bodies of these hams is not interfered with until the curing pickle has penetrated from the outside4 ,as it requires several weeks for the curing pickle to penetrate thoroughly into the deeper portions of these hams1 the bacillus is thus afforded a considerable interval in which to develop4 #ac4 ,the percentage of souring in the mild-cure hams could be greatly reduced without materially affecting the cure by pumping these hams with their own curing pickle1 which is usually a milder pickle than that employed in the regular cure2 and if the pumping were thorough the number of sours in these hams could be reduced to a small figure4 #ad4 ,the only way by which ham souring could be entirely eliminated from the larger packing establishments under the present methods of curing would be to handle the hams throughout under aseptic conditions1 and this1 for obvious reasons1 would be an impossibility4 ,the losses from ham souring may be materially reduced1 however1 by greater care in handling the hams and the adoption of precautionary measures designed to prevent the introduction of contaminated foreign matter into the bodies of the hams1 together with more thorough methods of pumping4 ,,acknowledgments4 ,in conclusion1 the writer desires to express his obligations to ,dr4 ,s4 ,e4 ,bennett1 of the ,inspection ,division1 inspector in charge at ,chicago1 for the assignment of trained meat inspectors to assist in the work1 as well as for kind assistance in obtaining data and material for laboratory study1 and to ,dr4 ,l4 ,e4 ,day1 of the ,pathological ,division1 who kindly prepared the sections which are figured and described in the present article4