& ,d$icat$ ,to ,de/anie2 ,) ,hopes ,h]  
,dream ( ,becom+ ,a vet]9>ian ,comes    
,true  ,special ,?anks to ,deborah      
,furness ( ! ,univ]sity ,college ,london
 = h] help1 & rese>*1 9 le>n+ ab\t ?is  
book1 & help+ me und]/& x bett]4        
,spell*eck$ ) www4!solutioncafe4com     
file :i* includes ! orig9al             
illu/rations4       ,see #bagha-;h4htm  
or #bagha-;h4zip3                       
7https3_/_/www4gut5b]g4org_/dirs_/#b_/a_
/g_/h_/bagha_/bagha-;h_/#bagha-;h4htm7  
or                                      
7https3_/_/www4gut5b]g4org_/dirs_/#b_/a_
/g_/h_/bagha_/bagha-;h4zip7             
,transcrib]'s ,note3        ,i try to   
edit my e-texts s !y c easily be us$ )  
voice       spee* programs1 ,i believe  
bl9d p & *ildr5 %\ld also       be able 
to enjoy ! _m books n[ available        
electronically4 ,i       use ! -- = an  
em-da%1 ) a space ei!r be=e or aft]     
x dep5d+ on its usage4 ,?is helps to    
keep c]ta9 programs       f squi%+ !    
words toge!r1 su* z d[n-/airs4 ,also to 

help voice spee* programs ,i've enclos$ 
upp] case text       betwe5 - &         
7-,,upp] ,,case ,,text71 & us$          
und]scores to       %[ *apt] & section  
head]s4 ,i also add$ a second           
cont5ts t %[s ! o!r sections ( ?is      
e-text4 ,?is       e-text 0 made ) a    
,top c text scann]1 ) a bit (           
correct+ "h & !re4        ,?is book is  
volume "o ( two4 ,x 0 lat] rework$ by   
,a4 ,m4       ,davies 9 #ahih "u ! title
 ,text-book ( ,zoology1       !n revis$ 
& rewritt5 by ,j4 ,t4 ,cunn+ham ab\t    
#aiji &       ,w4 ,h4 ,leigh-,%>pe ar\nd
 #aicb4 ,al?\gh ^! editions gave        
,wells ! ma9 cr$it1 mo/ ( ,wells' writ+ 
& all 8       draw+s 7 remov$2 only 8   
r\gh outl9e seems to h       be5 us$4 ,x
 0 re-publi%$ by ,univ]sity ,tutorial   
,press4        ,! ,fir/ ,edition1 z well
 z ,! ,second & ,revis$ ,edition        
7) dissections r$rawn by ,miss ,a4 ,c4  
,robb9s7 are us$ 9 ?is       e-text4 ,! 
,fir/ ,edition _h "s small m9or errors1 
z well z       dissection abbreviations 

t are %[n on ! ,dissection ,%eets1      
b no m5tion ( !m 0 li/$ 9 ! text4 ,c]ta9
 figures on       ! ,dissections ,%eets 
are miss+ 7su* z ,figures #a1 #b1 #d1 ) 
no m5tion to a #c1 z if ,mr4 ,wells drew
 a ,figure #c b f\nd x       0 n ne$$ & 
remov$ x f ! book74 ,r !n leav+       x 
z is1 ,i put  m>ks ar\nd my notes say+  
?+s l       ,no ,figure #c4 ,= ! ,second
 & ,revis$ ,edition ,wells 0       able 
to *ange "s ( ^! errors & miss+ p>ts1 b 
_m (       ! same pr9t+ tablets 7 us$ & 
) almo/ ea* addition       o!r ?+s 7    
remov$1 79 "o in/ance "o entire section 
f a *apt]71 & _m ( ! helpful sugge/ions 
7       %ort5$ or remov$ s o!r ?+s c\ld 
be expla9$ m4 ,9       an ideal v]sion (
 ! book bo? c\ld h be5 us$1 b )         
repr9t+ ! entire book f ! fir/ to !     
second editions       almo/ z _m ?+s 7  
lo/ z 7 ga9$1 s ,i've tri$ to           
indicate :]e bo? text g sep>ate pa?s ) !
 foll[+2       ,second ,edition only    
text & -,fir/ ,edition only text1- &    
also       ,l9es f ,second ,edition     

only4 & ,l9es f ,fir/ ,edition          
only4 7 m !n j a s5t5ce is add$ or      
remov$4 ,o!r       ?+s to notice is h[  
"s words are spelt or punctuat$         
diff]5tly ?r\gh\t ! book1 su* z2        
,blood ,vessels       ,blood-,vessels   
,bloodvessels       ,i've tri$ to keep  
^! z close to ! orig9al book z possible4
     ,univ]sity ,correspond5ce ,college 
,tutorial ,s]ies4  -,text-,book ,(      
,biology4  by  ,h4 ,g4 ,wells1 ,ba*elor 
( ,sci5ce1 ,london41 ,fell[ ( !         
,zoological ,society4 ,lectur] 9        
,biology at ,univ]sity ,tutorial        
,college4  ,) ,an ,introduction by ,g4  
,b4 ,h[es1 ,fell[ ( ! ,l9nean ,society1 
,fell[ ( ! ,zoological ,society4        
,assi/ant ,pr(essor ( ,zoology1 ,royal  
,college ( ,sci5ce1 ,london4        ,"p 
#a4-- ,v]tebrata4    ,cont5ts           
,introduction  ,preface  ,! ,rabbit--   
#a4 ,ext]nal ,=m & ,g5]al ,consid]ations
 #b4 ,! ,alim5t>y ,canal ( ! ,rabbit #c4
 ,! ,circulation #d4 ,! ,amoeba1 ,cells 
& ,tissue #e4 ,! ,skeleton #f4 ,muscle &

 ,n]ve #g4 ,! ,n]v\s ,sy/em #h4 ,r5al & 
,reproductive ,organs #i4               
,classificatory ,po9ts #aj4 ,que/ions & 
,ex]cises  ,! ,frog-- #a4 ,g5]al        
,anatomy #b4 ,! ,skull ( ! ,frog 7& !   
,v]tebrate ,skull g5]ally7 #c4 ,que/ions
 on ! ,frog  ,! ,dog-,fi%-- #a4 ,g5]al  
,anatomy #b4 ,que/ions on ! ,dog-,fi%   
,amphioxus-- #a4 ,anatomy #b4 ,!        
,developm5t ( ,amphioxus #c4 ,que/ions  
on ,amphioxus  ,developm5t-- ,!         
,developm5t ( ! ,frog ,! ,developm5t ( !
 ,f[l ,! ,developm5t ( ! ,rabbit ,!     
,!ory ( ,evolution ,que/ions on         
,embryology  ,miscellane\s ,que/ions    
,note on ,mak+ ,comp>isons  ,syllabus ( 
,practical ,"w   ,cont5ts "p #b  ,key = 
,dissection ,%eets1 & ,abbreviations    
-,introduction  ,9 ! ye> #ahhd ,i 0     
invit$ to give tuition by correspond5ce1
 9 ,biology4 ,al?\gh dispos$ at ! "t to 
ridicule ! idea ( imp>t+ in/ruction 9   
natural sci5ce by lett]1 ,i gladly      
accept$ ! opportunity ?us af=d$ me (    
asc]ta9+ = myself :at c\ld & c\ld n be  

accompli%$ 9 t direction4 ,anyone       
famili> ) ! scope ( biological enquiry1 
& ! me?ods ( biological in/ruction1 w n 
ne$ to be rem9d$ t x is only by ! mo/   
rigor\s employm5t ( precise directions =
 obs]vation1 t any good results are to  
be look$ = at ! h& ( ! elem5t>y /ud5t4  
,true to ?is pr9ciple1 ,i det]m9$ to    
issue to my correspond5ce pupils rigid  
in/ructions1 & to dem& 9 return fai?ful 
annotat$ draw+s ( facts obs]v$ 9 _!     
usage4 ,9 ! case ( two among ! few      
/ud5ts :o pass$ ?r\gh my h&s1 ! result  
f> exce$$ my mo/ sangu9e anticipations4 
,! notes s5t 9 by "o ( !m-- a man work+ 
at a di/ance1 alone & unaid$-- f>       
excell$ ^? wrung f _m a /ud5t plac$ "u !
 mo/ fav\rable surr\nd+s2 & _! promise =
 ! future has be5 fulfill$ to ! utmo/1 !
 individual 9 "q be+ n[ a recognis$     
inve/igator4 ,x ?us became cle> t1      
n-)-/&+ ! complex conditions ( "w 9 !   
biological field1 tuition by            
correspond5ce w\ld suffice to awak5 !   
lat5t abilities ( a naturally qualifi$  

enquir]4 ,! av]age memb]s ( a ,univ]sity
 ,correspond5ce ,class w be f\nd nei!r  
bett] nor worse ?an ^? ( any o!r1 & !y  
may !re=e pass unnotic$2 if h[ev]1 !    
correspond5ce sy/em ( tuition may furni%
 ! means ( ar\s+ a lat5t aptitude1 :5 ! 
possibilities ( o!r me?ods ( approa* are
 exclud$-- & 9 s do+1 ( elevat+ !       
individual to t position = :i* he 0 by  
nature qualifi$1 ensur+ him !           
introduction to ! "o sph]e ( lab\r = :i*
 he 0 born-- x w h creat$ its own       
def5ce1 & h m]it$ ! confid5ce ( all     
"r-?9k+ p4 ,! pluck+ ( "o su* br& f !   
burn+ is ample comp5sation = ! en]gy    
exp5d$ on any numb] ( av]age dull>ds1 :o
 b require to be left alone to f9d _!   
natural level4  ,mr4 ,wells' little book
 is av[$ly writt5 = exam9ation purposes1
 & 9 con=mity ) ! requirem5ts ( ! n[    
famili> type sy/em ( tea*+4 ,rec5t      
attempts h be5 made to depreciate ?is4  
,:ile af=d+ a discipl9e 9 detail$       
obs]vation & manipulation second to t ( 
no o!r bran* ( le>n+1 x provides = t    

d$uction & v]ification by :i* all sci5ce
 has be5 built up2 & ?is appe>s to me   
ample ju/ification = its ret5tion1 z !  
mo/ rational sy/em :i* c be to-day      
adopt$4 ,evid5ce t its alleg$ %ortcom+s 
are due r to defective h&l+ ?an to any  
inh]5t weakness ( its own1 w\ld n be    
difficult to produce4 ,al?\gh rigid 9   
its discipl9e1 x admits ( comm5tatorial 
treatm5t :i*1 :ile height5+ ! int]e/ ( !
 /ud5t1 is calculat$ to /imulate alike 8
 ambition & 8 imag9ation4 ,t ! si/]     
sci5ces ( ,botany & ,zoology fall "u "o 
discipl9e1 is express$ 9 ! ,engli% usage
 ( ! t]m ,biology4 ,exp]i5ce has %[n t !
 be/ "w 9 ei!r dep>tm5t has be5 produc$ 
by ^? :o h acquir$ on all-r\nd k ( at   
lea/ ! elem5t>y /ages ( bo?2 &1 t !     
advanc$ morphologi/ & physiologi/ are   
alike ! bett] = a famili>ity ) !        
pr9ciples-- n to say ) ! progressive    
advancem5t-- ( ea* o!r's doma91 is      
to-day und5iable4 ,^! & o!r alli$       
consid]ations1 r5d] x advisable t !     
elem5t>y facts ( morphology & physiology

 %\ld be pres5t$ to ! beg9n] side by    
side-- a pr9ciple too frequ5tly neglect$
 9 books :i*1 l ?is "o1 are specially   
writt5 = ! biological neophyte4 ,al?\gh 
! /ud5t is ! wis] = ! actual obs]vation 
( ! fact ( nature1 he becomes ! bett]   
only :5 able to apply !m1 z = example1  
by ! judici\s con/ruction ( elem5t>y    
g5]alizations1 su* z are introduc$ into 
! pages ( ?is "w4 ,s long z ^!          
g5]alizations1 reg>d$ z fir/ attempts to
 d$uce laws 9 ! =m ( g5]aliz$ /atem5t ( 
facts bas$ obs]vation1 are prop]ly      
introduc$ into an elem5t>y text-book1   
int5d$ = ! isolat$ work] cut (f f !     
lecture room1 _! int]calation is bo?    
heal?y & desirable4  ,mr4 ,wells has    
kept ^! precepts con/antly 9 m9d 9 !    
prep>ation ( 8 "w1 & 9 ! =mulation ( 8  
plans = its future ext5sion1 !reby      
enhanc+ ! value ( ! book itself1 & at ! 
same "t1 disc\rag+ ! sy/em ( pure cram1 
:i* is ali5 to ! discipl9e ( biological 
sci5ce4  ,g4 ,b4 ,h[es ,royal ,college (
 ,sci5ce1 ,s\? ,k5s+ton2 ,novemb] #cj1  

#ahib4    -,preface  ,no me?od ( /udy+--
 m especially :5 ! objects ( /udy are   
tangible ?+s-- c rival t prosecut$ "u ! 
direction & 9 ! con/ant pres5ce ( a     
tea*] :o has also a liv+ & vivid k ( !  
matt] :i* he h&les ) ! /ud5t4 ,9 ! ideal
 _w !re is a pl5tiful supply ( su*      
tea*]s1 & easy access to _! tea*+1 b 9  
?is real _w only a fav\r$ few enjoy ^!  
advantages4 ,?r\gh causes t _c be       
discuss$ "h1 a va/ numb] ( solit>y      
work]s are scatt]$ ?r\gh ! c\ntry1 to   
:om su/a9$ help 9 ?is =m is impossible1 
or possible only 9 days /ol5 f a ne$$   
vacation2 & to su* /ud5ts especially    
does ?is book appeal1 z well z to ^? m  
=tunate le>n]s :o are )9 rea* ( ord]ly  
in/ruction1 b anxi\s to save _! tea*]s' 
pati5ce & _! own "t by "s prelim9>y "w4 
,"o ( ! mo/ manife/ disadvantages (     
book-"w1 "u ! conditions ( ! solit>y    
work]1 is ! rigidity ( its expressions2 
if ! exact mean+ is d\btful1 he c n ask 
a "q4 ,?is has be5 kept 9 view ?r\gh\t2 
! writ] has1 above all1 s\ght to be     

explicit-- has1 sav+ ov]-sights1 us$ no 
uncommon or te*nical t]m )\t a def9ition
 or a cle> indication ( its mean+4  ,9  
?is /udy ( ,biology1 ! p]ception &      
memory ( =m is a v important factor     
inde$4 ,e /ud5t %\ld draw sket*es ( 8   
dissections1 & accu/om himself to copy+ 
book diagrams1 9 ord] to tra9 8 eye to  
p]ception ( details he might o!rwise    
disreg>d4 ,! draw+ requir$ is )9 ! rea* 
( all2 b = ^? :o are v inexp]i5c$1 trac+
 figures is a useful prelim9>y ex]cise4 
,by ! "t ! /ud5t has read ! ,circulation
 ( ! ,rabbit 7,sections #cd to #di71 he 
w be ready to beg9 dissection4 ,x is    
possible to hunt to dea? ev5 su* a s\nd 
educational maxim z ! ?+ be=e ! "n1 & we
 are p]suad$1 by a consid]able exp]i5ce1
 t dissection be=e "s su* prep>atory    
read+ is altoge!r a mi/ake4 ,at ! end ( 
! book is a syllabus 7) sugge/ions7 =   
practical "w1 orig9ally drawn up by !   
writ] = 8 own private use ) ! ev5+      
classes ( ! ,univ]sity ,tutorial        
,college-- classes ( /ud5ts work+ ma9ly 

9 _! sp>e "t = ! ,london exam9ation1 &  
at an enorm\s disadvantage1 z reg>ds !  
numb] ( h\rs available1 9 comp>ison ) ! 
leisurely /ud5ts ( a ,univ]sity         
laboratory4 ,?is syllabus may1 p]haps by
 itself1 s]ve a useful purpose 9 "s     
cases1 b 9 ?is ess5tial "p ( ! /udy !   
pres5ce ( "s exp]i5c$ ov]look] to       
advise1 w>n1 & correct1 is at fir/ almo/
 indisp5sable4  ,a few words may1 p]haps
 be said ) respect to ! design ( ?is    
volume4 ,x is manife/ly modell$ ^u !    
syllabus ( ! ,int]m$iate ,exam9ation 9  
,sci5ce ( ,london ,univ]sity4 ,t        
syllabus1 z at pres5t con/itut$1 appe>s 
to me to af=d consid]able scope = fairly
 effici5t biological /udy4 ,! f\r types 
dealt ) 9 ?is book are extremely        
conv5i5t = develop+ ! me?ods (          
comp>ative anatomy & morphological      
embryology4 ,)\t any ext5sive ref]5ce to
 relat$ organisms1 ^! f\r =ms1 &        
especially ! ?ree v]tebrata1 may be made
 to expla9 & illu/rate "o ano!r 9 a way 
t _c fail to be educational 9 ! true/   

s5se4 ,aft] deal+ ) ! rabbit1 !re=e1 z  
an organic me*anism1 our sections ^u !  
frog & dog-fi%1 & ^u developm5t1 are    
simply /atem5ts ( diff]5ces1 & a        
comm5t>y1 z x 71 ^u ! anatomy ( !       
mammalian type4 ,9 ! conclud+ *apt]1 a  
few sugge/ions ( ! mo/ elem5t>y ideas ( 
x is hop$ to make ?is fir/ "p ( our     
biological c\rse complete 9 itself1 & ( 
"s real & p]man5t value to ! /ud5t4 ,& !
 writ] is conv9c$ t n only is a con/ant 
insi/5ce ^u resemblances & diff]5ces1 & 
_! import1 intellectually ! mo/         
valuable1 b also ! mo/ int]e/+1 & !re=e 
! easie/1 way ( /udy+ animal anatomy4 ,t
 *aotic & brea?less cramm+ ( t]ms       
misund]/ood1 tabulat$ /atem5ts1 =mulat$ 
tips1 & li/s ( names1 9 :i* s _m /ud5ts1
 9 spite ( advice1 wa/e _! y\? is1 ,i   
s9c]ely hope1 z impossible ) ?is book z 
x is useless = ! purposes ( a ,london   
c&idate4 ,on ! o!r h&1 our *ief endeav\r
 has be5 to r5d] ! matt] ( ! book cle>1 
connect$1 progressive1 & easily         
assimilable4 ,9 ! second "p ,plants1    

,unicellul> ,organisms1 & ,inv]tebrata w
 be dealt )1 9 a wid] & less detail$    
view ( ! entire biological prov9ce4     
,l9es f ,fir/ ,edition only4    -,9 ?is 
volume1 we /udy f\r organisms1 & *iefly 
9 _!    relation to ea* o!r2 9 ! next1  
we %all /udy a numb] (    organisms     
l>gely 9 relation to _! environm5t4 ,9  
?is "p    our key note is ! evid5ce (   
inh]itance2 9 our second "p    x w be ( 
adaptation to circum/ances4-  ,?is book 
w spe$ily1 "u ! scrut9y ( ! critical    
read]1 reveal abundant weakness4 ,= ^! !
 au?or claims ! full cr$it4 ,= :atev]   
m]it x may posses1 he mu/ h[ev]1        
ackn[l$ge 8 pr(\nd indebt$ness to 8 =m] 
tea*]1 ,pr(essor ,h[es4 ,n only has !   
writ] enjoy$ 9 ! pa/ ! privilege (      
,pr(essor ,h[es' in/ruction & example1 b
 he has1 dur+ ! prep>ation ( ?is "w1    
receiv$ ! readie/ help1 advise1 &       
enc\ragem5t f him-- assi/ance z g5]\s z 
x 0 unm]it$1 & z unaffect$ z x 0        
valuable4     ,l9es f ,second ,edition  
only4    ,! publication ( a second &    

revis$ edition ( ?is ,"p af=ds    !     
au?or an opportunity ( express+ 8 s5se (
 ! g5]al    k9dl9ess ( 8 review]s1 & !  
help !y h him 9 improv+    ?is maid5    
ef=t4 ,to no "o is !re v\*saf$ su* a    
facility 9    ! discov]y ( errors 9 a   
book z to its au?or1 s soon z x has     
pass$ beyond 8 p[] ( correction4 ,h5ce !
 g5]al tone (    enc\ragem5t 7& 9 "s    
cases ! decid$ approval7 ( !    memb]s (
 ?is t]m9ation to a p]iod ( consid]able 
remorse &    appreh5sion4  ,i h be5 able
 ?r\gh _! c\nsel1 & ! exp]i5ce ,i h _h  
:ile us+ ?is book 9 tea*+1 to correct   
sev]al pr9t]'s errors & to alt] v>i\s   
ambigu\s or mislead+ expressions1 z well
 z to br+ ! book up to date aga9 9 "o or
 two p>ticul>s4  ,my ?anks are          
p>ticul>ly due to my fri5d ,miss        
,robb9s1 :o has v k9dly r$rawn !        
occasionally r blottesque figures ( !   
fir/ edition4 ,n only h ^! plates ga9$  
imm5sely 9 grace & accuracy1 b ! lett]+ 
is n[ di/9ct-- an improvem5t t any /ud5t
 :o has _h to hunt my ref]5ce lett]s 9 !

 fir/ edition w at once appreciate4  ,h4
 ,g4 ,wells ,novemb]1 #ahib4 ,fir/      
,edition4 ,decemb]1 #ahic4 ,second      
,edition4    -,! ,rabbit4  #a4 ,ext]nal 
,=m & ,g5]al ,consid]ations4  ,section  
#a4 ,x is unnecess>y to ent] ^u a       
description ( ! appe>ance ( ?is famili> 
type1 b x is n p]haps sup]flu\s1 z we   
proce$ to consid] its anatomy1 to call  
att5tion to "o or two po9ts 9 its       
ext]nal1 or ext]nally app>5t /ructure4  
,mo/ ( our read]s "k t x belongs to t "o
 ( two prim>y animal divisions :i* is   
call$ ! v]tebrata1 & t ! di/9ctive      
feature :i* place x 9 ?is division is ! 
possession ( a sp9al column or backbone1
 really a s]ies ( small r+-l bones1 !   
v]tebrae 7,figure #a v4b47 /rung toge!r1
 z x 71 on ! ma9 n]ve axis1 ! sp9al cord
 7,figure #a s4c474 ,?is sp9al column c 
be felt along ! neck & back to ! tail4  
,?is tail is small1 tilt$ up1 &         
conspicu\sly :ite b5ea?1 & x s]ves z a  
recognition m>k to guide ! "y :51 dur+  
fe$+1 an al>m is giv5 & a bolt is made =

 ! burr[s4 ,9 ^? m primitive 7old] &    
simpl]-fa%ion$7 v]tebrata1 ! fi%es1 !   
tail is mu* l>ge & f> m important1 z    
comp>$ ) ! re/ ( ! body1 ?an x is 9 mo/ 
( ! air-inhabit+ v]tebrates4 ,9 ! =m] x 
is inv>iably a great muscul> mass to    
propel ! body =w>d2 9 ! latt] x may     
disappe>1 z 9 ! frog1 be simply a       
fea!r-be>+ /ump1 z 9 ! pigeon1 a fly    
flick]1 z 9 ! c[ or horse1 a fur cape 9 
squirrel1 or be o!rwise r$uc$ & modifi$ 
to meet special requirem5ts4   ,section 
#b4 ,at ! =e end1 or z ,engli% zoologi/s
 pref] to say1 ant]ior end1 ( ! v]tebral
 column ( ! rabbit1 is ( c\rse ! skull1 
conta9+ ! ant]ior portion ( ! n]ve axis1
 ! bra9 7,figure #a br474 ,betwe5 ! head
 & :at is call$ ! body1 9 ! m re/rict$  
s5se ( ! ^w1 is ! neck4 ,! neck gives   
fre$om ( movem5t to ! head1 enables !   
animal to look ?is way & t1 to turn its 
e>s ab\t to det]m9e ! direction ( a     
s\nd1 & to p]=m endless motions 9       
connexion ) bit+ & s =? easily4 ,we may 
note t 9 types :i* swim ?r\gh ! wat]1 ! 

neck dose n appe>-- 9 ! fi% & frog1 =   
in/ance-- & ! head simply wid5s out z "o
 passes back to ! body4 ,! high         
resi/ance (f]$ by wat] necessitates ?is 
t5d5cy to a cig> or %ip outl9e1 j z x   
has det]m9$ ! cig> %ape ( ! ord9>y fi%  
torp$o4   ,section #c4 ,9 ! body ( !    
rabbit1 z exam9$ f ! outside1 we c make 
out by feel+ two di/9ct regions1 j z we 
might 9 ! body ( a man2 ant]iorily a    
bony cage1 hav+ ! ribs at ! sides1 a    
rod-l bone 9 ! front1 ! /]num 7,figure  
#a -/4-1 /m471 & ! backbone beh9d1 &    
call$ ! *e/ or ?orax2 & po/]iorily a "p 
call$ ! abdom51 :i* has no bony         
protection ov] its belly1 or v5tral     
surface4 ,^! p>ts toge!r ) ! neck       
con/itute ! trunk4 ,z a consequ5ce ( ^! 
?+s1 9 ! backbone ( ! rabbit !re are f\r
 regions3 ! neck1 or c]vical "p1 consi/+
 ( sev5 v]tebrae1 ! ?oracic "p ( twelve 
jo9$ to ribs1 ! abdom9al 7also call$ !  
lumb>7 region ( sev5 )\t ribs1 & ! tail 
or caudal ( ab\t fifte54 ,betwe5 ! lumb>
 & caudal come f\r v]tebrae1 ! sacral1  

:i* t5d to run toge!r into a bony mass z
 ! animal gr[s old1 & :i* =m a firm     
atta*m5t = ! base ( ! h9d limb4         
,section #d4 ,! ?orax & abdom5 are      
sep>at$ by a p>tition1 ! diaphragm      
7,figure #a dia474 ,?is /ructure is     
di/9ctive ( t class ( ! v]tebrata call$ 
mammals1 & :i* includes man1 mo/ ( !    
l>g] & common] l& animals1 & :ales &    
manatee4 ,we %all f9d lat] t x is       
ess5tially connect$ ) ! p]fection ( !   
air brea?+ to :i* ?is gr\p has atta9$4  
,ano!r *>act]i/ic %>$ by all mammals1 & 
by no o!r creature1 is ! pres5ce ( hair4
 ,9 birds we h an equally *>act]i/ic    
cov] 9 ! fea!rs1 ! frog is nak$1 & !    
fi%es we f9d ei!r nak$ sk9s or scales4  
,section #e4 ,! %ort /rong =e limbs are 
adapt$ to ! burr[+ habit1 & h five      
digits2 ! h9d limbs are v mu* long] &   
muscul>1 enable ! animal to progress    
rapidly by %ort leaps1 & !y h f\r toes4 
,if ! /ud5t ?9ks x wor? :ile to attempt 
to rememb] ! numb] ( digits-- x is !    
fault ( exam9]s if any value dose atta* 

to su* intr9sically valueless facts-- he
 %\ld associate ! numb] #ed 7#e 9 front1
 #d beh9d7 ) ! rabbit1 & obs]ve t ) !   
frog ! rev]se is ! case4   ,section #f4 
,we may note "h ! mean+ ( c]ta9 t]ms we 
%all be con/antly employ+4 ,! head end (
 ! rabbit is ant]ior1 ! tail end        
po/]ior1 ! backbone side ( ! body-- !   
upp] side 9 life-- is dorsal1 ! brea/ & 
belly side1 ! l[] side ( ! animal1 is   
v5tral4 ,if we imag9e ! rabbit sawn     
asund]1 z x 71 by a plane pass+ ?r\gh ! 
head & tail1 t w\ld be ! m$ian plane1 & 
p>ts on ei!r side ( x are lat]al1 & left
 or "r accord+ z !y lie to ! animal's   
left or "r4 ,9 a limb1 or 9 ! int]nal   
organs1 ! "p ne>e/ ! c5tral organ1 or   
axis1 is proximal1 ! m remote or t]m9al 
p>ts are di/al4 ,= in/ance1 ! m\? is    
ant]iorly plac$1 ! tongue on its v5tral 
wall2 ! tongue is m$ian1 ! eyes are     
lat]al1 & ! f+]s are di/al to ! elb[4 ,!
 /ud5t mu/ accu/om himself to ^! words1 
& avoid1 9 8 descriptions1 ! use ( su*  
t]ms z above1 bel[1 outside1 :i* v>y ) !

 position 9 :i* we conceive ! animal    
plac$4   ,section #g4 ,s mu* = ! g5]al  
=m2 we may note a few facts ( g5]al k1 9
 connection ) ! rabbit's life-activity4 
,9 a day ( ! rabbit's life a consid]able
 am\nt ( "w is done-- ! animal runs hi!r
 & ?i!r1 = in/ance2 9 o!r words1 a c]ta9
 mass ( matt] is mov$ ?r\gh space1 & = t
 we "k =ce mu/ be ex]t$4 ,:5ce comes !  
=ce8   ,section #h4 ,we f9d ! rabbit    
occupies a consid]able am\nt ( its "t 9 
tak+ 9 vegetable matt]1 consi/+ *iefly (
 m or less complex combu/ible & un/able 
organic comp\nds4 ,x is a pure          
veget>ian1 & a rem>kably mod]ate dr9k]4 
,"s b only a small proportion1 ( !      
vegetable matt] x eats1 leaves its body 
comp>atively un*ang$1 9 little pellets1 
! faeces1 9 ! process ( defaecation4 ,= 
! re/ we h to acc\nt4   ,section #i4 ,we
 f9d1 also1 t ! rabbit brea!s air into  
its lungs1 :i* is return$ to ! atmosph]e
 ) a less5$ am\nt ( oxyg51 & ! addition 
( a p]ceptible am\nt ( c>bon dioxide4 ,!
 rabbit also ?r[s (f1 or excretes1 a    

fluid1 ! ur9e1 :i* consi/s ( wat] ) a   
c]ta9 p>tially oxydis$ sub/ance conta9+ 
nitrog51 & call$ urea1 & o!r less       
important salts4 ,! organs )9 ! body1 by
 :i* ! ur9e is sep>at$1 are call$ !     
kidneys4   ,section #aj4 ,repeat+ ^!    
facts 9 o!r words1 ! rabbit takes into  
its body complex & un/able organic      
comp\nds conta9+ nitrog51 c>bon1        
hydrog51 a c]ta9 am\nt ( oxyg51 a small 
quantity ( sulphur1 & /ill small] am\nts
 ( o!r elem5ts4 ,x also brea!s 9 oxyg54 
,section #aa4 ,x returns a c]ta9 reject$
 "p ( its food comp>atively un*ang$4    
,besides ?is1 x returns c>bon dioxide & 
wat]1 :i* are completely oxydis$1 & v   
simple & /able bodies1 & urea-- a less  
completely oxydis$ comp\nd1 b a v simple
 "o comp>$ ) ! food con/itu5ts4         
,section #ab4 ,n[ ! *emi/ tells u t :5 a
 /able body is =m$1 or :5 an un/able    
comp\nd decomposes into simpl] /able    
ones1 =ce is evolv$4 ,! oxydation (     
c>bon1 = in/ance1 9 ! fireplace1 is !   
=mation ( ! /able comp\nd call$ c>bon   

dioxide1 & light & heat are evolv$4 ,!  
explosion ( dynamite1 aga9 is !         
decomposition ( an un/able comp\nd4     
,h5ce1 we beg9 to p]ceive t =ce-- !     
vital =ce-- :i* keeps ! rabbit mov+1 is 
suppli$ by ! decomposition & p>tial     
oxydation ( comp\nds cont9u$ 9 its food1
 to c>bon dioxide1 wat]1 urea1 & small] 
quantities ( o!r sub/ances4   ,section  
#ac4 ,?is is ! r\ghe/ /atem5t ( ! case  
possible1 b x w give ! g5]al idea       
und]ly+ our next *apt]s4 ,we %all       
consid] h[ ! food ent]s ! body & is tak5
 up into ! sy/em1 h[ x is convey$ to !  
muscles 9 ! limbs1 to ! n]ve c5tres1 &  
to :]ev] "w is done1 to be !re decompos$
 & p>tially oxydis$1 & f9ally h[ !      
products ( its activity-- ! kata/ases1 (
 :i* ! ?ree pr9cipal are c>bon dioxide1 
wat]1 & urea-- are remov$ f ! body4     
,section #ad4 ,!re are "o or two        
comp>atively mod]n t]ms t we may note   
"h4 ,?is decomposition ( un/able *emical
 comp\nds1 releas+ en]gy1 is call$      
kataboly4 ,a rev]se process1 :i* has a  

less conspicu\s "p 9 our fir/ view ( !  
animal's life action1 by :i* un/able    
comp\nds are built up & en]gy /or$1 is  
call$ anaboly4 ,! kata/ases are !       
products ( kataboly4   ,section #ae4 ,9 
an ord9>y animal1 locomotion & o!r      
activity pr$om9ate ov] nutritive        
processes1 :i* fact we may express1 9 ! 
t]ms j giv51 by say+ t kataboly prevails
 ov] anaboly4 ,an animal1 z we h j      
expla9$1 is an app>atus = !             
decomposition & p>tial oxydation ( c]ta9
 comp\nds1 & ^! are obta9$ ei!r directly
 or indirectly-- ?r\gh o!r animals1 9 ! 
case ( meat-eat]s-- f ! vegetable k+dom4
 ,z ! /ud5t w le>n e>ly 9 8 botanical   
read+1 ! typical plant has1 9 its gre5  
col\r+ matt]1 *lorophyll1 a trap to cat*
 ! radiat+ en]gy ( ! sun1 & to          
accompli%1 by ! absorption ( t en]gy1 ! 
syn!sis 7build+ up7 ( ^? organic        
comp\nds :i* ! animal de/roys4 ,!       
typical plant is1 on :ole1 passive &    
syn!tic1 or anabolic2 ! typical animal1 
active & katabolic2 & ! excess (        

kataboly ov] anaboly 9 ! animal is      
comp5sat$ = by ! anabolic "w /or$ up1 z 
x 71 by ! plant1 :i* is1 directly or    
indirectly1 ! animal's food4    #b4 ,!  
,alim5t>y ,canal ( ! ,rabbit  ,section  
#af4 ,figure #a repres5ts ! g5]al       
anatomy ( ! rabbit1 b is especially     
int5d$ to %[ ! alim5t>y 7 food7 canal1  
%ort5$ to a c]ta9 ext5t1 & ) !          
proportions alt]$1 9 ord] to avoid any  
confus+ complications4 ,x is evid5tly   
simply a coil$ tube-- coil$ = ! sake (  
pack+-- ) occasional dilatations1 & ) "o
 side-%unt1 ! caecum 7cae471 into :i* ! 
food ent]s1 & is return$ to ! ma9 l9e1  
aft] probably absorb5t action1          
imp]fectly und]/ood at pres5t4 ,a spiral
 fold 9 ?is cul-de-sac bottom-(-sack1   
:i* is m>k$ ext]nally by con/rictions1  
has a directive influ5ce on !           
circulation ( its cont5ts4 ,! /ud5t %\ld
 sket* ,figure #a once or twice1 & make 
himself famili> ) ! ord] & names ( !    
p>ts be=e proce$+4 ,we h1 9 succession1 
! m\? 7,m471 sep>at$ f ! nasal passage  

7,na47 above ! palate2 ! ph>ynx 7ph471  
:]e ! "r & left nasal passages op5 by ! 
po/]ior n>es into ! m\?2 ! oesophagus   
7oes472 ! bag-l /oma*1 its left         
7,section #f7 end be+ call$ ! c>diac    
7cd4/471 & its "r ! pyloric end 7py472 !
 ,u-%ap$ duod5um 7ddnm47 & ! v long &   
greatly coil$ ileum 7il474 ,! duod5um & 
ileum toge!r =m ! small inte/9e2 & !    
ileum is dilat$ at its di/al end into a 
?ick-wall$ sacculus rotundus 7s4r471    
beyond :i* po9t comes ! l>ge inte/9e4 ,!
 colon 7co47 & rectum 7r47 cont9ue ! ma9
 l9e ( ! alim5t>y canal2 b1 at ! beg9n+ 
( ! l>ge inte/9e1 !re is also ins]t$ a  
great side-%unt1 ! caecum 7cae471 end+  
bl9dly 9 a fle%y v]mi=m app5dix 7v4ap474
 ,! figure w indicate h[ ! p>ts are     
relat$ bett] ?an any v]bal description  
c4 ,betwe5 ! coil+ alim5t>y tube & !    
body walls is a space1 into :i* ! /ud5t 
cuts :5 he beg9s dissect+2 ?is is !     
p]itoneal cavity 7pt474 ,a ?91 transp>5t
 membrane1 ! mes5t]y1 holds ! inte/9es 9
 place1 & b9ds !m to ! dorsal wall ( ?is

 p]itoneal space4   ,section #ag4 ,!    
food /uffs ( an animal1 ! un/able       
comp\nds de/9$ ultimately to be work$   
into its life1 & to leave x aga9 9 ! =m 
( kata/ases 7,section #ac71 fall into   
two ma9 divisions4 ,! fir/ ( ^! includes
 ! non-nitrog5\s food /uffs1 conta9+    
ei!r c>bon toge!r ) hydrog5 & oxyg5 9 ! 
proportion ( ,h#b,o 7! c>bo-hydrates71  
or c>bon & hydrog5 )\t oxyg5 7!         
hydroc>bons74 ,! second division consi/s
 ( ! nitrog5\s mat]ials1 conta9+ also   
c>bon1 hydrog51 a c]ta9 am\nt ( oxyg51  
sulphur1 & possibly o!r elem5ts4 ,among 
! c>bohydrates1 ! commone/ are />* &    
cellulose1 :i* are insoluble bodies1 &  
sug>1 :i* is soluble4 ,! hydroc>bons1   
fats1 oils1 & s on1 =m a comp>atively   
small proportion ( ! rabbit's diet2 !   
prov]b ( oil & wat] w rem9d ! /ud5t t ^!
 are insoluble4 ,! nitrog5\s bodies h _!
 type 9 ! album5 ( an egg2 & muscle     
sub/ance & ! less modifi$ liv+          
protoplasm ( plants1 a consid]able      
proportion ( ! sub/ance ( se$s1 bulbs1 &

 s on1 are album9\s bodies1 or proteids4
 ,^! also are insoluble bodies1 or :5   
soluble1 w n diffuse easily ?r\gh animal
 membranes4   ,section #ah4 ,n[ !       
ess5tial problem :i* ! dige/ive canal ( 
! rabbit solves is to get ^! insoluble1 
or quasi-insoluble1 bodies into its     
blood & sy/em4 ,!y h to pass someh[ into
 ! circulation ?r\gh ! walls ( !        
alim5t>y canal4 ,9 ord] t a comp\nd %\ld
 diffuse ?r\gh a membrane1 x mu/ be bo? 
soluble & diffusible1 & !re=e an        
ess5tial prelim9>y to ! absorption (    
nutritive matt] is its conv]sion into a 
diffusible soluble =m4 ,?is is effect$  
by c]ta9 fluids1 =m$ ei!r by ! walls ( !
 alim5t>y canal or by c]ta9 organs call$
 gl&s1 :i* op5 by ducts into x2 all ^!  
fluids conta9 small quantities ( organic
 comp\nds ( ! class call$ f]m5ts1 & ^!  
are ! active ag5ts 9 ! *ange4 ,! soluble
 =m ( ! c>bohydrates is sug>2 proteids c
 be *ang$ into !1 ( c\rse1 *emically    
equival5t b soluble & diffusible !      
peptones2 & fats & oils und]go a m      

complicat$1 b f9ally simil> *ange4      
,section #ai4 ,we %all discuss !        
/ructure & action ( -a gl&- gl&s a      
little m fully 9 a subsequ5t *apt]4 ,"h 
we w simply say t !y are organs =m+ ea* 
its *>act]i/ic fluid or secretion1 &    
s5d+ x by a conduit1 ! duct1 to ! po9t  
:]e its pres5ce is requir$4 ,! saliva 9 
our m\?s1 te>s1 & p]spiration1 are      
examples ( ! secretions ( gl&s4         
,section #bj4 ,9 ! mon? ( ! rabbit !    
food is act$ ^u by ! tee? & saliva4 ,!  
saliva conta9s ptyal91 a f]m5t conv]t+  
/>* into sug>1 & x also s]ves to moi/5 !
 food z x is gr\nd up by ! *eek tee?4 ,x
 does n act on fat to any appreciable   
ext5t4 ,! tee? ( ! rabbit are %[n 9     
,figure ,,xviii41 ,%eet #d4 ,! incisor  
tee? 9 front1 two pairs above & "o pair 
bel[ 7i471 are simply employ$ 9 grasp+ !
 food2 ! *eek tee?-- ! premol>s 7pm47 & 
mol>s 7m47 beh9d-- triturate ! food by a
 complicat$ motion ov] ea*4 ,_! cr[ns   
are flat = ?is purpose1 ) h>d] ridges   
runn+ across !m4   ,section #ba4 ,?is   

gr9d+ up ( ! food 9 ! m\? inv>iably     
occurs 9 h]bivor\s animals1 :]e !re is a
 consid]able am\nt ( />* & comp>atively 
little hydroc>bon 9 ! food4 ,by f9ely   
divid+ ! food1 x ensures its intimate   
contact ) ! dige/ive f]m5t1 ptyal94 ,9  
su* meat-eat]s z ! cat & dog1 :]e little
 />*y matt] & mu* fat is tak51 ! saliva 
is1 ( c\rse1 ( less importance1 & ?is   
ma/ication does n occur4 ,! *eek tee? ( 
a dog 7,section #ia71 & m s ( a cat1 are
 %>p1 & us$ = gnaw+ (f fragm5ts ( food1 
:i* are swall[$ at once4 ,betwe5 !      
incisors & premol>s ( a dog come !      
*>act]i/ic bit+ tee?1 or can9es1 abs5t 9
 ! rabbit4   ,section #bb4 ,! /ud5t w   
probably ask :y ! *eek tee?1 :i* are all
 simil> 9 appe>ance1 are divid$ into    
premol>s & mol>s4 ,! rabbit has a set ( 
milk mol>s-- a milk d5tition-- :i* are  
foll[$ by ! p]man5t tee?1 j z 9 man4 ,^?
 *eek tee? ( ! second set1 :i* h        
pr$ecessors 9 ! fir/ s]ies1 are call$   
premol>s2 ! ones po/]ior to ^! are !    
mol>s4   ,section #bc4 ,aft] ma/ication1

 ! food is work$ by ! tongue & *eeks    
into a saliva-soak$ bolus & swall[$4 ,! 
passage d[n ! oesophagus is call$       
deglutition4 ,9 ! /oma* x comes "u !    
influ5ce ( ! ga/ric juice1 =m$ 9 little 
gl&ul> pits 9 ! /oma* wall-- ! ga/ric   
7,figure ,,viii4 ,%eet #c7 & pyloric    
gl&s4 ,?is fluid is di/9ctly acid1 its  
acidity be+ due to ab\t "o-t5? p] c5t ( 
a hundr$ ( hydro*loric acid1 & x !re=e  
/ops any fur!r action ( ! ptyal91 :i* c 
act only on neutral or slightly alkal9e 
fluids4 ,! ga/ric juice does n act on   
c>bo-hydrates or hydroc>bons to any v   
noticeable degree4 ,its ess5tial prop]ty
 is ! conv]sion ( proteids into         
peptones1 & ! f]m5t by :i* ?is is       
effect$ is call$ peps94 ,milk conta9s a 
peculi> soluble proteid1 call$ case91   
:i* is precipitat$ by a special f]m5t1 !
 r5net-f]m5t1 & ! insoluble proteid1 !  
curd1 ?us obta9$ is !n act$ on by !     
peps94 ,9 ! manufacture ( *eese1 !      
r5netf]m5t obta9$1 f ! /oma* ( a calf is
 us$ to curdle ! milk4   ,section #bd4  

,aft] ! food has und]gone dige/ion 9 !  
/oma* x passes into ! duod5um1 ! ,u-%ap$
 loop ( inte/9e imm$iately succe$+ !    
/oma*4 ,! duod5um is sep>at$ f ! /oma*  
by a r+-l muscul> valve1 ! pylorus2 ?is 
valve belongs to ! class ( muscles call$
 sph9ct]s1 :i*1 "u ord9>y circum/ances1 
are clos$1 b :i* relax to op5 ! circul> 
c5tral ap]ture4 ,! valve at ! anus1 :i* 
reta9s ! faeces1 is ano!r in/ance ( a   
sph9ct]4   ,section #be4 ,! food at ?is 
/age is call$ *yme2 x is an acid & s\p-l
 fluid-- acid ?r\gh ! influ5ce ( !      
ga/ric juice4 ,! temp]ature ( ! animal's
 body is suffici5tly high to keep mo/ ( 
! fat 9 ! food melt$ & float+ 9 oily    
drops2 mu* ( ! />*1 has be5 *ang$ to    
sug>1 & ! solid proteids to soluble     
peptones1 b _m fragm5ts ( mat]ial /ill  
float un*ang$4   ,section #bf4 ,x meets 
n[ ) ! bile1 a gre5i% fluid secret$ by t
 l>ge & conspicu\s gl& ! liv]4 ,! bile  
is n simply a dige/ive secretion1 l !   
saliva or ! ga/ric juice2 x conta9s     
matt]s de/9$ to mix 91 & aft] a c]ta9   

am\nt ( *ange to be pass$ out ( ! body  
)1 ! faeces2 among ^! sub/ances1 ( :i*  
"s portion is d\btless excretory1 are   
comp\nds conta9+ sulphur-- ! bile salts4
 ,!re is also a col\r+ matt]1 bili v]d91
 :i* may possibly also be excretory4 ,if
 ! /ud5t w comp>e ,sections #aj & #aa1  
he w notice t 9 ^? p>agraphs no acc\nt  
is tak5 ( ! sulphur among ! kata/ases1 !
 acc\nt does n balance1 & he w at once  
see t "h probably is ! miss+ item on !  
outgo+ side4 ,! bile1 ?r\gh ! pres5ce ( 
^! salts1 is /rongly alkal9e1 & s /ops !
 action ( ! ga/ric juice1 & prep>es = t 
( ! pancreas1 :i* c act only 9 an       
alkal9e m$ium4 ,! f]m5tive action ( !   
bile is trifl+2 x dissolves fats1 to a  
c]ta9 ext5t1 & is antiseptic1 t is1 x   
prev5ts putrefaction to :i* ! *yme might
 be liable2 x also seems to act z a     
natural purgative4   ,section #bg4 ,!   
bile1 z we %all see lat]1 is by no means
 ! sole product ( ! liv]4   ,section    
#bh4 ,! pancreatic juice1 ! secretion ( 
! pancreas is rem>kable z act+ on all ! 

food /uffs t h n already become soluble4
 ,x emulsifies fats1 t is1 x breaks1 !  
drops up into extremely small globules1 
=m+ a milky fluid1 & x fur!rmore has a  
f]m5tive action ^u !m2 x splits !m up   
into fatty acids1 & ! soluble body      
glyc]9e4 ,! fatty acids comb9e ) alkal9e
 sub/ances 7,section #bf7 to =m bodies  
:i* belong to ! *emical gr\p ( ,soaps1 &
 :i* are soluble also4 ,! pancreatic    
juice also attacks any proteids t h     
escap$ ! ga/ric juice1 & conv]ts !m into
 peptones1 & any residual />* into sug>4
 ,h5ce by ?is /age1 9 ! duod5um1 all !  
food con/itu5ts notic$ 9 ,section #ag   
are *ang$ into soluble =ms4 ,!re are    
probably1 ?ree di/9ct f]m5ts 9 !        
pancreatic juice act+ respectively on   
/>*1 fat1 & proteid1 b !y h n be5       
isolat$1 & ! t]m pancreat9 is sometimes 
us$ to sugge/ ! ?ree toge!r4   ,section 
#bi4 ,a succus ent]icus1 a saliva-l     
fluid secret$ by num]\s small gl&s 9 !  
inte/9e wall 7,brunn]'s gl&s1           
,lieb]kuhnian follicles71 probably aids1

 to an unkn[n b comp>atively small      
ext5t1 9 ! dige/ive processes4          
,section #cj4 ,! walls ( ! :ole ( !     
small inte/9e are engag$ 9 ! absorption 
( ! soluble results ( dige/ion4 ,9 !    
duod5um1 especially1 small processes1 ! 
villi project into ! cavity1 & be+1 l ! 
small hairs ( velvet pile1 & z ?ickly   
set1 give its inn] coat a velvety       
appe>ance4 ,9 a villus we f9d 7,figure  
,,ix41 ,%eet #c7 a s]ies ( small        
blood-vessels & ) x ano!r vessel call$ a
 lacteal4 ,! lacteals run toge!r into   
l>g] & l>g] bran*es until !y =m a ma9   
trunk1 ! ?oracic duct1 :i* op5s into !  
blood circulation at a po9t ne> ! he>t2 
b ( ?is we %all speak fur!r lat]4 ,!y   
conta91 aft] a meal1 a fluid call$ *yle4
   ,section #ca4 ,emulsifi$ fats pass   
into ! *yle4 ,wat] & diffusible salts   
c]ta9ly pass into ! ve94 ,! c\rse tak5  
by ! peptones is unc]ta91 b ,pr(essor   
,fo/] fav\rs ! *yle 9 ! case ( !        
rabbit-- ! /ud5t %\ld read 8 ,text-book 
( ,physiology1 ,"p #b1 ,*apt] #a1       

,section #aa1 if int]e/$ 9 ! fur!r      
discussion ( ?is "q4   ,section #cb4 ,! 
processes t occur 9 ! rema9+ portions ( 
! alim5t>y canal are imp]fectly         
und]/ood4 ,! caecum is s l>ge 9 ! rabbit
 t x mu/ almo/ c]ta9ly be ( consid]able 
importance4 ,9 c>nivor\s animals x may  
be s mu* r$uc$ z to be practically      
abs5t4 ,an important factor 9 ! diet ( !
 h]bivor\s animals1 & "o abs5t f ! food 
( ! c>nivora1 is t c>bohydrate1 ! build+
 mat]ial ( all gre5-meat- food1         
cellulose1 & !re is "s gr\nd = ?9k+ t ! 
caecum is probably a region ( special   
f]m5tive action ^u x4 ,! pancreatic     
juice1 x may be not$1 ex]cises a slight 
dige/ive activity ^u ?is sub/ance4      
,section #cc4 ,wat] is mo/ l>gely       
absorb$ 9 ! l>ge inte/9e1 & 9 x !       
reject$ 7ma9ly insoluble7 portion ( !   
food gradually acquires its d>k col\r & 
o!r faecal *>act]i/ics4    #c4 ,!       
,circulation  ,section #cd4 ,! next ?+  
to consid] is ! di/ribution ( ! food    
mat]ial absorb$ ?r\gh ! walls ( !       

alim5t>y canal to ! liv+ & active p>ts (
 ! body4 ,?is is "o ( ! functions ( !   
s]ies ( /ructures-- he>t &              
blood-vessels1 call$ ! circulation1     
circulatory sy/em1 or vascul> sy/em4 ,x 
is n ! only function4 ,! blood also     
c>ries ! oxyg5 f ! lungs to ! v>i\s p>ts
 :]e "w is done & kataboly occurs1 & x  
c>ries away ! kata/ases to ! po9ts :]e  
!y are excret$-- ! c>bon dioxide & "s   
wat] to ! lungs1 wat] & urea to !       
kidneys1 sulphur comp\nds ( "s k9d to ! 
liv]4   ,section #ce4 ,! blood 7,figure 
#d1 ,%eet #b7 is n homog5e\s2 "u ! l[   
p[] ( ! microscope x may be se5 to      
consi/ (--     7#a47 a cle> fluid1 !    
plasma1 9 :i* float--     7#b47 a few   
transp>5t col\rless bodies ( indef9ite &
 *ang+    %ape1 & hav+ a c5tral bright] 
portion1 ! nucleus ) a /ill    bright]  
dot !re9 ! nucleolus-- ! :ite corpuscles
 7w4c471 &     7#c47 flat r\nd discs1   
)\t a nucleus1 ! r$ corpuscles 7r4c471  
greatly m num]\s ?an ! :ite4   ,section 
#cf4 ,! *yle ( ! lacteals passes1 z we h

 said1 by ! ?oracic duct directly into !
 circulation4 ,x ent]s ! left v5a cava  
sup]ior 7l4v4c4s47 ne> :]e ?is jo9s !   
jugul> ve9 7ex4j47 7see ,figure #a1     
,%eet #b1 ?4d47 & goes on at once ) !   
re/ ( ! blood to ! he>t4 ,! small ve9s (
 ! villi1 h[ev]1 :i* also help suck up !
 soluble nutritive mat]ial1 are n       
directly cont9u\s ) ! o!r body ve9s1 !  
sy/emic ve9s2 !y belong to a special    
sy/em1 &1 runn+ toge!r into l>g] & l>g] 
bran*es1 =m ! li5o ga/ric 7l4g4v47 &    
mes5t]ic 7m4v47 ve9s1 :i* unite to =m ! 
portal ve9 7p4v47 :i* ent]s ! liv]      
7l4v47 & !re breaks up aga9 into small] 
& small] bran*es4 ,! v f9e/             
ramifications ( ?is spread+ network are 
call$ ! 7liv]7 capill>ies1 & ^! aga9    
unite to =m at la/ ! hepatic ve9 7h4v47 
:i* ent]s ! v5a cava inf]ior 7v4c4i471 a
 m$ian vessel1 runn+ directly to ! he>t4
 ,?is capill>y network 9 ! liv] is      
probably connect$ ) *anges requisite    
be=e ! rec5tly absorb$ mat]ials c ent] !
 g5]al blood curr5t4   ,section #cg4 ,! 

/ud5t has probably already he>d ! t]ms  
ve9 & art]y employ$4 ,9 ! rabbit a ve9  
is a vessel br++ blood t[>ds ! he>t1    
:ile an art]y is a vessel conduct+ x    
away4 ,ve9s are ?9-wall$1 & !re=e       
flabby1 a conspicu\s purple :5 full (   
blood1 & :5 empty ?r\gh ble$+ & collaps$
 sometimes difficult to make out 9      
dissection4 ,!y are =m$ by ! union (    
less] factors4 ,! portal breaks up into 
less] bran*es )9 ! liv]4 ,art]ies h ?ick
 muscul> & ela/ic walls1 ?ick en\gh to  
prev5t ! blood %[+ ?r\gh1 & are !re=e   
pale p9k or :ite & keep _! r\nd %ape4   
,section #ch4 ,! he>t ( ! rabbit is     
divid$ by p>titions into f\r *amb]s3 two
 upp] ?9-wall$ ones1 ! auricles 7au471 &
 two l[] ones1 bo?1 & especially ! left1
 ) v muscul> walls1 ! v5tricles 7vn474  
,! "r v5tricle 7r4vn47 & auricle 7r4au47
 communicate1 & ! left v5tricle 7l4vn47 
& auricle 7l4au474   ,section #ci4 ,!   
blood com+ f all p>ts ( ! body1 p>tly   
robb$ ( its oxyg5 & conta9+ mu* c>bon   
dioxide & o!r kata/ases1 ent]s ! "r     

auricle ( ! he>t ?r\gh ?ree great ve9s1 
! m$ian v5a cava inf]ior f ! po/]ior    
p>ts ( ! body1 & ! pair$ v5ae cavae     
sup]iores f ! ant]ior4 ,) ! beat+ ( !   
he>t1 describ$ bel[1 x is =c$ into ! "r 
v5tricle & f !re ?r\gh ! pulmon>y art]y 
7p4a47 se5 9 ! figure pass+ "u ! loop ( 
! aorta 7ao47 to ! lungs4   ,section    
#dj4 ,! lungs 7lg4 ,figure #a1 ,%eet #a7
 are m\ld$ to ! %ape ( ! ?oracic cavity 
& he>t2 !y communicate ) ! ph>ynx by !  
tra*ea 7tr4 9 ,figure #a1 ,%eet #a7 or  
w9dpipe1 & are made up ( a tissue (     
cont9ually bran*+ & dim9i%+ air-tubes1  
:i* end at la/ 9 small air-sacs1 !      
alveoli4 ,! f9al bran*es ( ! pulmon>y   
art]ies1 ! lung capill>ies1 lie 9 !     
walls ( ^! air-sacs1 & are sep>at$ f !  
air by an extremely ?9 membrane ?r\gh   
:i* ! oxyg5 diffuses into1 & ! c>bon    
dioxide escapes f1 ! blood4   ,section  
#da4 ,! me*anism ( respiration w be     
und]/ood by ref]5ce to ,figure #c1 ,%eet
 #b4 ,x w be not$1 9 dissect+ t ! lungs 
h %runk away f ! walls ( ! ?orax2 ?is   

collapse occurs directly an ap]ture is  
made 9 ! ?orax wall1 & is 9 "p due to _!
 extreme ela/icity4 ,9 life ! cavity ( !
 ?orax =ms an air-tight box1 betwe5 :i* 
& ! lungs is a slight space1 ! pleural  
cavity 7pl4c47 l9$ by a moi/ membrane1  
:i* is also reflect$1 ov] ! lungs4 ,!   
?orax wall is muscul> & bony1 & resi/s !
 atmosph]ic pressure on its out] side1 s
 t ! lungs be=e ?is is cut ?r\gh are    
kept di/5d$ to ! size ( ! ?oracic cavity
 by ! pressure ( ! air )9 !m4 ,9        
inspiration 7or brea?+-97 ! ribs are    
rais$ by ! ext]nal int]co/al 7,anglice1 
betwe5-ribs1 e4i4c4m47 & o!r alli$      
muscles1 & ! diaphragm 7dia47 contracts 
& becomes flatt]2 ! air is consequ5tly  
suck$1 9 z ! lungs foll[ ! movem5t ( !  
?orax wall4 ,9 expiration ! int]co/als &
 diaphragm relax & all[ ! ela/ic recoil 
( ! lungs to come into play4 ,! ?oracic 
wall is simultane\sly depress$ by !     
muscles ( ! abdom9al area1 ! diaphragm  
?ru/ =w>ds1 z ! result ( ! displacem5t &
 compression ( ! alim5t>y visc]a ?us    

br\ght ab\t4 7r4r4r4 9 ! ,figure m>k    
ribs47   ,section #db4 ,! oxyg5 & c>bon 
dioxide are n c>ri$ 9 exactly ! same way
 by ! blood4 ,! /ud5t w "k f 8 *emical  
read+ t nei!r ( ^! gases is v soluble1 b
 c>bon dioxide is suffici5tly s 9 an    
alkal9e fluid to be convey$ by ! liquid 
plasma4 ,! oxyg5 h[ev]1 ne$s a special  
portative me*anism 9 ! col\r+ matt] ( ! 
r$ corpuscles1 ! haemoglob91 ) :i* x    
comb9es weakly to =m oxy-haemoglob9 ( a 
bright r$ col\r1 & decompos+ easily 9 ! 
capill>ies 7! f9e/ vessels betwe5 !     
art]ies & ve9s71 to release ! oxyg5     
aga94 ,! same comp\nd occurs 9 all true 
v]tebrata1 & 9 ! blood-fluid ( ! worm2 9
 ! crayfi% a simil> sub/ance1           
haemocyan91 :i* :5 oxyg5at$ is blue1 &  
:5 deoxydiz$ col\rless1 dis*>ges ! same 
function4   ,section #dc4 ,! blood      
returns f ! lungs to ! left auricle     
7l4au47 by ! pulmon>y ve9s1 hidd5 9 !   
,figure by ! he>t1 passes !nce to !     
?ick-wall$ left v5tricle 7l4vn471 & on  
into ! aorta 7ao474   ,section #dd4 ,!  

beat+ ( ! he>t is1 ( c\rse1 a succession
 ( contractions & expansions ( its      
muscul> wall4 ,! contraction1 or sy/ole1
 comm5ces at ! base ( ! v5ae cavae &    
passes to ! auricles1 driv+ ! blood be=e
 x into ! v5tricles1 :i* !n contract    
%>ply & drive x on into ! aorta or      
pulmon>y art]y2 a pause & !n a          
dilatation1 ! dia/ole foll[s4 ,! fl[ ( !
 blood is det]m9$ 9 "o direction by !   
v>i\s valves ( ! he>t4 ,no valves occur 
9 ! op5+ ( ! sup]ior cavae b an imp]fect
 "o1 ! ,eu/a*ian valve1 protects !      
inf]ior cava2 ! direction ( ! he>t's    
contraction prev5ts any excessive       
back-fl[ into ! ve9s1 & ! onw>d1 t5d5cy 
is enc\rag$ by ! suck ( ! dia/ole ( !   
v5tricles4 ,betwe5 ! left v5tricle &    
auricle is a valve made up ( two flaps (
 sk91 ! mitral valve1 ! edges ( ! flaps 
be+ connect$ ) ! walls ( ! v5tricle     
?r\gh ! int]m$iation ( small muscul>    
?reads1 ! *ordae t5d9ae1 :i* /ret*      
across its cavity to little muscul>     
pill>s1 ! papill>y muscles2 ^! atta*m5ts

 prev5t ! mitral valve f flapp+ back    
into ! auricle1 & z ! blood fl[s into & 
accumulates 9 ! v5tricle x gets beh9d ! 
flaps ( ! valve & presses its edges     
toge!r4 ,:5 ! sy/ole ( ! v5tricle       
occurs1 ! increas$1 t5sion ( ! blood    
only closes ! ap]ture ! tight]1 & !     
curr5t passes on into ! aorta1 :]e we   
f9d ?ree wat*-pocket valves1 ) ! pocket 
turn$ away f ! he>t1 :i* are also clos$ 
& tight5$ by any attempt at             
regurgitation 7back-fl[74 ,a simil>     
process occurs on ! "r side ( ! he>t1 b 
"h1 in/ead ( a mitral valve ( two flaps 
betwe5 auricle & v5tricle1 we h a       
tricuspid valve ) ?ree4 ,! ?ickness ( ! 
muscul> walls1 9 view ( ! less] di/ance 
?r\gh :i* x has to =ce ! blood1 -are- is
 less = ! "r v5tricle ?an ! left4       
,section #de4 ,! foll[+ are ! *ief      
bran*es ( ! aorta4 ,! /ud5t %\ld be able
 to foll[ !m ) c]ta9ty 9 dissection2 !y 
are all display$ 9 ! ,figure2 b x mu/ n 
be imag9$ = a mom5t t famili>ity ) ?is  
diagram w obviate ! necessity = !       

practical "w2 7947 is ! innom9ate art]y2
 x =ks into 7s4cl4a47 ! "r subclavian1 &
 7r4c4c47 ! "r common c>otid4 ,ea*      
c>otid splits at ! angle ( ! jaw into an
 int]nal & an ext]nal bran*4 ,! left    
common c>otid1 7l4c4c47 arises f ! base 
( ! innom9ate199 7l4s4cl4a47 ! left     
subclavian1 directly f ! aorta4 ,! aorta
 n[ curves r\nd to ! dorsal middle l9e1 
& runs d[n z se5 9 ,figure #a1 ,%eet #a 
7d4ao47 & ,figure #a1 ,%eet #b 7d4ao474 
,small bran*es are giv5 (f to ! ribs1 & 
!n comes ! m$ian coeliac 7coe4a47 to !  
/oma* & sple51 ! m$ian sup]ior mes5t]ic 
7s4mes4a47 to ! ma9 portion ( ! inte/9e1
 & ! inf]ior mes5t]ic 7p4m4a47 to !     
rectum4 ,note t no ve9s to ! inf]ior v5a
 cava correspond to ^! art]ies-- ! blood
 !y supply go+ back by ! portal ve9     
7p4v474 ,! pair$ r5al art]ies 7r4a47    
supply ! kidneys1 & ! common iliacs     
7c4il4a47 ! h9d legs1 splitt+ into !    
int]nal iliacs 7i4il4a47 & ! femoral    
7f474     ,l9es f ,second ,edition only4
    ,! /ud5t %\ld note t ! only art]ies 

9 ! middle l9e    are ^? supply+ !      
alim5t>y canal4     ,l9es f ,fir/       
,edition only4    99 -,! figure is      
inaccurate1 & repres5ts ! left common   
c>otid    z aris+ f ! aortic ar*4-      
,section #df4 ,! di/ribution ( ! ve9s ( 
! rabbit has only a sup]ficial          
p>allelism ) art]ies4 ,! *ief factors ( 
v5a cava inf]ior are ! hepatic ve9      
7h4v471 :i* receives ! liv] blood1 !    
r5al ve9s 7r4v471 f ! kidneys1 !        
ilaeo-lumb>1 f ! abdom9al wall1 & !     
ext]nal 7e4il4v47 & int]nal ilias       
7i4il4v472 ) ! exception ( ! r5al ve9s  
none ( ^! run side by side ) art]ies4 ,!
 sup]ior cavae 7r4 & l4v4c4s47 are =m$  
by ! union ( int]nal 7i4j47 & ext]nal   
jugul> 7e4j47 ve9s ) a subclavian       
7s4cl4v47 f ! =e limb4 ,! t]m pre-caval 
ve9 is sometimes us$ = sup]ior cava4 ,! 
att5tion1 ( ! /ud5t is call$ to ! small 
azygos ve9 7az47 runn+ into ! "r v5a    
cava sup]ior1 & =m+ ! only asymmetrical 
7n-balanc+7 feature ( ! ve9s 9 front ( !
 he>t2 x br+s blood back f ! ribs ( !   

?orax wall1 & is ( int]e/ ma9ly because 
x answ]s to an enorm\s ma9 vessel1 ! "r 
po/-c>d9al s9us1 9 fi%es4 ,!re are      
sp]matic art]ies & ve9s 7s4v4 & a47 to !
 g5ital organs4 ,all ^! vessels %\ld be 
pati5tly dissect$ out by ! /ud5t1 &     
drawn4   ,section #dg4 ,betwe5 ! f9al   
bran*es ( ! art]ies & ! fir/ f9e factors
 ( ! ve9s1 & jo9+ !m1 come ! sy/emic    
capill>ies4 ,^! smalle/ & ultimate      
ramifications ( ! circulation p5etrate e
 liv+ "p ( ! animal1 s t if we c\ld     
isolate ! vascul> sy/em we %\ld h !     
complete =m ( ! rabbit 9 a closely-me%$ 
network4 ,x is 9 ! capill>ies t !       
ex*ange ( gases occurs & t nutritive    
mat]ial passes out to ! tissues &       
kata/ases 9 f !m2 !y are ! ess5tial     
factor 9 ! circulatory sy/em ( !        
mammal-- ve9s1 art]ies1 & he>t simply   
exi/ to remove & replace _! cont5ts4 ,! 
details ( ! bran*+ ( ! pulmon>y art]y & 
! pulmon>y ve9s ne$ n deta9 u n[4       
,section #dh4 ,summ>is+ ! c\rse ( !     
circulation1 />t+ f ! "r v5tricle1 we   

h-- pulmon>y art]y1 pulmon>y capill>ies1
 pulmon>y ve91 left auricle1 left       
v5tricle1 aorta1 art]ies1 & sy/emic     
capill>ies4 ,aft] ?is1 f all p>ts except
 ! sple5 & alim5t>y canal1 ! blood      
returns to sy/emic ve9s1 sup]ior or     
inf]ior cavae1 "r auricle1 & "r         
v5tricle4 ,! blood f ! /oma* sple51 &   
inte/9es h[ev]1 passes via ?r\gh !      
portal ve9 to ! liv] capill>ies & !n    
?r\gh ! hepatic ve9 to inf]ior cava1 & s
 on4 ,mat]ial leaves ! blood to be      
excret$ 9 lungs1 kidneys1 by ! sk9 7z   
p]spiration71 & else:]e4 ,new mat]ial   
ent]s mo/ conspicu\sly2     7a7 by !    
portal ve9s portal ve9s &     7b7 by !  
?oracic duct & left sup]ior cava4       
,section #di4 ,! foll[+ table summ>ises 
:at we h le>nt up to ! pres5t ( !       
physiology ( ! ,rabbit1 consid]$ z a    
me*anism us+ up food & oxyg5 & dis5gag+ 
en]gy3--     -,air ,nitrog5444 return$  
un*ang$4    ,oxyg5444 ?r\gh ,pulmon>y   
,ve9 to-- see #c4     -,food            
,c>bo-,hydrates 7,/>*1 ,sug>1           

,cellulose47 ,sug>4    ,prote94         
,peptones4    ,fat 7little 9 ,rabbit47  
,glyc]9e1 & fatty acids 9 s\ps4         
,reject$ matt] got rid ( 9 ,defaecation4
     #a;a4 ,*yle 9 ,lacteals go+ via    
?r\gh ,?oracic ,duct & ,left    ,sup]ior
 ,cava to-- see #b4     #a;b4 ,ve9s (   
,villi--    ,portal ,ve9--    ,liv]--   
,hepatic ,ve9 & ,inf]ior ,cava to-- see 
#b4     #b4 ,"r side ( he>t2 !n to      
lungs1 & !n to-- see #c4     #c4 ,left  
side ( he>t2 :5ce to ,sy/emic ,art]ies &
 ,capill>ies4     #d4 ,! tissues &      
-,kataboly4     #e4 ,urea 78,liv]7      
,kidney & ,sweat ,gl&s    ,,co#b ,lungs 
,h#b,o ,lungs1 ,kidney1 ,sweat ,gl&s    
,o!r ,sub/ances ,ma9ly by ,kidney1 ,liv]
 & ,alim5t>y ,canal    #d4 ,! ,amoeba4  
,cells1 & ,tissue  ,section #ej4 ,we h  
?us se5 h[ ! nutritive mat]ial is tak5  
into ! animal's sy/em & di/ribut$ ov]   
its body1 & incid5tally1 we h not$ h[ ! 
resultant products ( ! creature's       
activity are remov$4 ,! ess5ce ( ! :ole 
process1 z we h already /at$1 is !      

decomposition & p>tial oxydation ( c]ta9
 complex *emical comp\nds to wat]1 c>bon
 dioxide1 a l[ nitrog5\s body1 :i*      
f9ally takes ! =m ( urea1 & o!r         
sub/ances4 ,we may n[ g on to a m       
detail$ /udy1 ! microscopic /udy1 or    
hi/ology1 ( ! tissues 9 :i* metaboly &  
kataboly occur1 b be=e we d ?is x w be  
conv5i5t to glance = a mom5t at ano!r ( 
our animal types-- ! ,amoeba1 ! l[e/ z !
 rabbit is ! highe/1 9 our s]ies4       
,section #ea4 ,?is is %[n 9 ,figure     
,,iii41 ,%eet #c1 z x w\ld appe> "u ! l[
 p[] ( ! microscope4 ,we h a mass ( a   
cle>1 transp>5t1 greyi% sub/ance call$  
protoplasm1 granul> 9 places1 & ) a     
cle>] bord]2 )9 ?is is a d5s] portion   
call$ ! nucleus1 or endopla/ 7n471 :i*1 
"u ! microscope1 by transmitt$ light1   
appe> bright]1 & )9 t a /ill d5s] spot1 
! nucleolus 7ns47 or endopla/ule4 ,!    
protoplasm is m or less ext5sively      
excavat$ by fluid spaces1 vacuoles2 "o  
cle>] circul> space or vacuole1 :i* is  
inv>iably pres5t1 appe>s at int]vals1   

enl>ges gradually1 & !n vani%es         
abruptly1 to reappe> aft] a brief       
int]val2 ?is is call$ ! contractile     
vacuole 7c4v474 ,! amoeba is con/antly  
*ang+ its %ape1 :5ce its old] "n ( !    
,proteus animalcule1 ?ru/+ out masses ( 
its sub/ance 9 "o direction1 & )draw+ f 
ano!r1 & h5ce sl[ly creep+ ab\t4 ,^!    
?ru/-out p>ts1 9 its outl9e1 are call$  
pseudopodia 7ps474 ,by means ( !m x     
gradually creeps r\nd & encloses its    
food4 ,little p>ticles ( nutritive matt]
 are usually to be detect$ 9 ! homog5e\s
 protoplasm ( its body2 commonly ^! are 
surr\nd$ by a drop ( wat] tak5 9 ) !m1 &
 ! drop ( wat] is !n call$ a food       
vacuole4 ,! process ( tak+ 9 food is    
call$ +e/ion4 ,! amoeba1 9 all          
probability1 p]=ms ess5tially ! same    
*emical process z we h summ>is$ 9       
,sections #aj1 #aa1 #ab2 x +e/s food1   
dige/s x 9 ! food vacuoles & builds x up
 into its body protoplasm1 to und]go    
kataboly & furni% ! =ce ( its motion-- !
 contractile vacuole1 is probably       

respiratory & p]haps excretory1         
accumulat+ & !n1 by its sy/ole 7comp>e  
,section #dd71 =c+ out ( its body1 !    
wat]1 c>bon dioxide1 urea1 & o!r        
kata/ases1 :i* are =m$ concomitantly )  
its activity4 ,! amoeba reproduces      
itself 9 ! simple/ way2 ! nucleus       
occasionally divides into two portions &
 a wid5+ fissure 9 ! protoplasm ( !     
animal's body sep>ates "o f ! o!r4 ,x is
 impossible to say t "o is ! p>5t cell1 
& ! o!r ! (fspr+2 ! amoeba we m]ely     
p]ceive1 0 "o & is n[ two4 ,x is curi\s 
to note1 !re=e1 t ! amoeba is1 9 a s5se1
 immortal-- t ! liv+ nucleus ( "o ( ^!  
m9ute creatures t we exam9e to-day "u a 
microscope may h conceivably drawn1 out 
an unbrok5 ?read ( life s9ce ! remote/  
epo*s ( ! _w's hi/ory4 ,al?\gh no sexual
 int]c\rse c be obs]v$1 !re is reason to
 believe t a process ( suppos$          
cannabalism1 9 :i* a l>g] amoeba may    
occasionally engulph a small] "o1 is    
really a conjugative reproductive       
process1 & foll[$ by increas$ vitality &

 division4   ,section #eb4 ,n[ if !     
/ud5t w comp>e ,section #ce1 he w see t 
9 ! :ite blood corpuscles we h a v      
rem>kable resemblance to ! amoeba2 !    
contractile vacuole is abs5t1 b we h !  
protoplasmic body1 ! nucleus &          
nucleolus1 & ^? creep+ fluctuations (   
%ape ?r\gh ! ?ru/+ out & )drawal (      
pseudopodia1 :i* con/itute amoeboid     
motion4 ,!y also multiply1 9 ! same way1
 by division4   ,section #ec4 ,x is n   
only 9 ! :ite corpuscle ( ! blood t we  
f9d ?is resemblance2 9 all ! firm] p>ts 
( ! body we f9d1 on microscopic         
exam9ation1 simil> little blebs (       
protoplasm1 & at an e>ly /age (         
developm5t ! "y rabbit is simply "o mass
 ( ^! protoplasmic bodies4 ,_! division 
& multiplication is an ess5tial         
condition1 ( gr[?4 ,?r\gh an un=tunate  
accid5t1 ^! protoplasmic blebs1 :i*     
con/itute ! liv+ basis ( ! animal body1 
h come to be /yl$ cells1 ?\gh ! t]m     
corpuscles is f> m appropriate4         
,section #ed4 ,! ^w is cell sugge/s     

some?+ enclos$ by firm & def9ite walls1 
& x 0 fir/ employ$ 9 vegetable hi/ology4
 ,unlike ! typical cells ( animals1 !   
cells ( mo/ plants are n nak$           
protoplasm1 b protoplasm enclos$ 9 a    
wall ( sub/ance 7cell wall7 call$       
cellulose4 ,! pres5ce ( ?is cellulose   
cell wall1 & ! consequ5t necessity (    
fe$+ entirely ^u liquids & gases t soak 
?r\gh x in/ead ( be+ able to +e/ a      
portion ( solid food is inde$1 ! prim>y 
di/9ction betwe5 ! vegetable & ! animal 
k+doms1 z ord9>ily consid]$4   ,section 
#ee4 ,?r\gh\t life1 millions ( ^! cells 
reta9 _! prim>y *>act]s1 & con/itute !  
:ite corpuscles ( blood1 phagocytes1 &  
connective tissue corpuscles2 o!rs aga91
 engage 9 ! =mation ( mat]ial r\nd      
!mselves1 & lie1 9 su* cases1 z gri/le &
 bone1 emb$d$ 9 ! sub/ance !y h =m$2    
o!rs aga91 und]go great *anges 9 =m &   
int]nal /ructure1 & become p]man5tly    
modifi$ into1 = in/ance1 n]ve fibres &  
muscle sub/ance4 ,! v>i\s sub/ances     
aris+ 9 ?is way ?r\gh ! activity ( cells

 are call$ tissues1 ! build+ mat]ials ( 
t complex ?+1 ! animal body4 ,s9ce su* a
 creature z ! rabbit is =m$ ?r\gh !     
co-op]ation ( a va/ multitude ( cells1 x
 is call$ multicellul>2 ! amoeba1 on !  
o!r h&1 is unicellul>4 ,! rabbit may be 
?us reg>d$ z a va/ community ( amoeboid 
creatures & _! products4   ,section #ef4
 ,figure ,,iv41 ,%eet #c repres5ts1     
diagrammatically1 embryonic tissue1 (   
:i*1 to beg9 )1 ! :ole animal consi/s4  
,! cells are all liv+1 capable ( divid+ 
& simil>1 b z developm5t proce$s1 !y    
diff]5tiate1 "s take on "o k9d ( duty   
7function71 & "s ano!r1 l boys tak+ to  
diff]5t trades on leav+ s*ool1 & wide   
diff]5ces 9 /ructure & int]dep5d5ce     
become app>5t4   ,section #eg4 ,x is    
conv5i5t to divide tissues into ?ree    
classes1 ?\gh ! divisions are by no     
means cle>ly m>k$1 nor h !y any         
sci5tific value4 ,! fir/ ( ^! comprises 
tissues compos$ :olly1 or ) ! exception 
( an almo/ imp]ceptible cem5t+ sub/ance1
 ( cells2 ! second division includes !  

skeletal tissues1 ! tissue ( mes5t]y1 & 
! connective & basem5t tissue ( mo/ ( ! 
organs1 tissues :i*1 g5]ally speak+1    
consi/ ( a matrix or emb$d+ sub/ance1   
=m$ by ! cells & outside ( !m1 z well z 
! cells !mselves2 &1 ?irdly1 muscul> &  
n]v\s tissue4 ,we %all /udy ! =m] two 9 
?is *apt]1 & def] ! ?ird division until 
lat]4   ,section #eh4 ,! out] lay] ( !  
sk9 7! epid]mis71 ! inmo/ l9+ ( !       
alim5t>y canal1 ! l9+ ( ! body cavity1 &
 ! inn] l9+s ( blood-vessels1 gl&s1 &   
v>i\s ducts con/itute our fir/ division4
 ,! g5]al "n = su* tissues is epi!lium4 
,:5 ! cells are m or less flatt5$1 !y =m
 squam\s epi!lium 7,figure ,,vi47 su* z 
we f9d l9+ ! inside ( a man's *eek 7f   
:i* ! cells sq4ep4 7 tak57 or cov]+ !   
mes5t]y ( v>i\s types-- sq4end4 are f ! 
mes5t]y 7,section #af7 ( a frog4 ,a %ort
 cyl9droidal =m ( cell makes up column> 
epi!lium1 se5 typically 9 ! cells cov]+ 
! villi ( ! duod5um 7,figure ,v474 ,?is 
epi!lium ( ! villi has ! out] bord]     
curi\sly /riat$1 & ?is is usually spok5 

( z lead+ t[>ds ciliat$ epi!lium1 to be 
describ$ imm$iately4 ,! epi!lium ( !    
epidid]mis is /ratifi$-- t is to say1   
has _m ?icknesses ( cells2 ! deep] lay]s
 are alive & divid+ 7/ratum mucosum71   
:ile ! m sup]ficial are increas+ly      
flatt5$ & dri] z ! surface is approa*$  
7/ratum corneum7 & are cont9ually be+   
rubb$ (f & replac$ f bel[4   ,section   
#ei4 ,9 ! bran*+ air-tubes ( ! lung1 !  
c5tral canal ( ! sp9al cord1 & 9 !      
uret]s ( ! rabbit1 & 9 mo/ o!r types1 9 
v>i\s organs1 we f9d ciliat$ epi!lium   
7,figure ,,vii474 ,?is is column> or    
cubical 9 =m1 & ) ! free edge curi\sly  
modifi$ & beset ) a numb] ( hair-l      
processes1 ! cilia1 by :i*1 dur+ ! life 
( ! cell1 a wav+ motion is su/a9$ 9 "o  
direction4 ,?is motion assi/s 9 ma9ta9+ 
a curr5t 9 ! cont5ts ( ducts :i* are l9$
 ) ?is tissue4 ,! motion is indep5d5t ( 
! g5]al life ( ! animal1 s long z !     
con/itu5t cell /ill lives1 & s x is easy
 = ! /ud5t to witness x himself ) a     
microscope hav+ a #a_/d-;in* or         

#a_/f-;in* objective4 ,v f9e cilia may  
be se5 by g5tly scrap+ ! ro( ( a frog's 
m\? 7! cells figur$ are f ?is s\rce71 or
 ! gill ( a rec5tly kill$ mussel1 &     
m\nt+ at once 9 wat]1 or1 bett]1 9 a v  
weak solution ( common salt4   ,section 
#fj4 ,! l9+ ( gl&s is secretory         
epi!lium2 ! cells are usually cubical or
 polygonal 7#h1 g4ep471 & !y display 9 !
 mo/ *>act]i/ic =m :at is call$         
metabolism4 ,anaboly 7see ,section #ad7 
we h def9$1 z a *emical *ange 9 an upw>d
 direction-- less /able & m complex     
comp\nds are built up 9 ! processes (   
vegetable & animal activity t[>ds       
protoplasm2 kataboly is a *emical runn+ 
d[n2 metaboly is a m g5]al t]m1 cov]+   
all vital *emical *anges4 ,! products ( 
! action ( a gl&ul> epi!lium are        
metabolic products1 mat]ial d]iv$ f !   
blood is work$1 up )9 ! cell1 n         
necess>ily ) conspicu\s ga9 or loss (   
en]gy1 & dis*>g$ into ! gl& space4 ,!   
mo/ /rik+ case ( ?is action is 9 !      
goblet cells t are f\nd among ! villi2  

^! are simply gl&s ( "o cell1 unicellul>
 gl&s1 & 9 ,figure ,v4 we see ?ree /ages
 9 _! action3 at g4c4#a mat]ial         
7secretion7 is se5 =m+ 9 ! cell1 at     
g4c4#b x approa*es ! out] bord]1 & at   
g4c4#c x has be5 dis*>g$1 leav+ a holl[$
 cell4 ,usually h[ev]1 ! escape (       
secret$ matt] is n s conspicu\s1 & !    
gl&-cells are collect$ z ! l9+ ( pits1  
simple1 z 9 ! ga/ric1 pyloric1 &        
,lieb]kuhnian gl&s 7,figure ,,viii41    
,sections #bc1 #bi71 or bran*+ l a tree 
or a bun* ( grapes 7,figure r4g471 z 9  
,brunn]'s gl&s 7,section #bi7 !         
pancreas1 & ! saliv>y gl&s4 ,! saliv>y  
gl&s1 we may m5tion1 are a pair int]nal 
to ! po/]ior v5tral angle ( ! jaw1 !    
sub-maxill>y2 a pair ant]ior to ^!1 !   
sub-l+ual2 a pair po/]ior to ! jaw b5ea?
 ! e>1 ! p>otid1 & a pair b5ea? ! eye1 !
 infra orbital4   ,section #fa4 ,! liv] 
is ! mo/ complicat$ gl& 9 ! body        
7,figure ,x474 ,! bile duct 7b4d47      
bran*es aga9 & aga91 & ends at la/ 9 !  
f9al pits1 ! lobuli 7lb471 :i* are l9$ )

 secretory epi!lium1 & tightly pack$1 & 
squeeze ea* o!r into polygonal =ms4 ,!  
blood supply f :i* ! bile w\ld appe> to 
be ma9ly extract$1 is br\ght by ! portal
 ve91 b ?is blood is altoge!r unfit = ! 
nutrition ( ! liv] tissue2 = ?is latt]  
purpose a bran* ( ! coeliac art]y1 !    
hepatic s]ves4 ,h5ce 9 ! tissue ( ! liv]
 we h1 bran*+ & int]weav+ among !       
lobuli1 ! small bran*es ( ! bile duct   
7b4d471 :i* c>ries away ! bile =m$1 !   
portal ve9 7p4v471 ! hepatic art]y      
7h4a471 & ! hepatic ve9 7h4v474 7,comp>e
 ,section #de47 ,figure ,x4b %[s a      
lobule2 ! portal ve9 & ! art]y ramify   
r\nd ! lobules-- are int]-lobul>1 t is  
7int]1 betwe572 ! hepatic ve9 beg9s 9 ! 
middle ( ! lobules 7intra-lobul>71 &    
receives _! blood4 7,comp>e ,x4a47      
,besides its function 9 ! manufacture ( 
! excretory1 dige/ive1 & auxili>y bile1 
! liv] p]=ms o!r duties4 ,x appe>s to   
act z an inspector ( ! assimilation     
mat]ial br\ght 9 by ! portal ve94 ,!    
villi1 = in/ance1 w absorb ars5ic1 b ?is

 is arre/$ & ?r[n d[n 9 ! liv]4 ,a ?ird 
function is ! =mation ( :at w\ld seem to
 be a /ore ( c>bo-hydrate1 glycog51     
ma9ly x w\ld appe>1 f ! sug> 9 ! portal 
ve91 ?\gh also1 v probably1 f nitrog5\s 
mat]ial1 ?\gh ?is may occur only "u     
exceptional conditions4 ,f9ally1 !      
nitrog5\s kata/ates1 =m$ 9 ! work+ (    
muscle & n]ve1 & return$ by !m to !     
blood = excretion1 are n at t /age 9 !  
=m ( urea4 ,:atev] =m !y assume1 !y     
und]go a fur!r metabolism into urea be=e
 leav+ ! body1 & ! pres5ce ( consid]able
 quantities ( ?is latt] sub/ance 9 !    
liv] sugge/s ?is z a f\r? function ( ?is
 organ-- ! elaboration ( urea4          
,section #fb4 ,simil> f a physiological 
po9t ( view1 to ! secretory gl&s :i* =m 
! dige/ive fluids are ^? :i* furni%     
lubricat+ fluids1 ! la*rymal gl&1 &     
,h>d]ian gl&s 9 ! orbit int]nally to !  
eye1 & po/]ior & ant]ior to x           
respectively1 ! sebace\s gl&s 7oil gl&s7
 connect$ ) ! hair1 & ! anal & p]9eal   
gl&s4 ,! secretions ( excretory gl&s are

 remov$ f ! body2 *ief among !m are !   
sweat gl&s & kidneys4 ,! sweat gl&s are 
microscopic tubul> gl&s1 t]m9at+        
int]nally 9 a small coil 7,figure       
,,viii4 s4g47 & are scatt]$ ?ickly ov] !
 body1 ! wat] ( _! secretion be+        
con/antly remov$ by evaporation1 & !    
small p]c5tage ( salt & urea rema9+ to  
accumulate z dirt1 & ! *ief reasonable  
excuse = wa%+4 ,! kidney /ructure is %[n
 diagrammatically 9 ,figure #e1 ,%eet   
#g4 ,a great numb] ( bran*+ & /raight   
loop$1 tubuli 7little tubes7 conv]ge on 
an op5 space1 ! pelvis4 ,t[>ds ! out]   
lay]s 7cortex7 ( ! kidney1 ^! tubuli    
t]m9ate 9 little dilatations into :i*   
tangl$ knots ( blood-vessels project3 ! 
dilatations are call$ ,b[man's capsules 
7,b4c471 & ea* coil ( bloodvessel a     
glom]ulus 7gl474 ,9 ! capsules1 wat] is 
dra9$ f ! blood2 9 ! tubuli1 urea & o!r 
salts 9 ! ur9e are secret$ f a bran*+   
network ( vessels4   ,section #fc4 ,9   
all ! epi!lial tissues t we h consid]$  
we h "o feature 9 common3 !y are cells1 

ea* equival5t to ! amoeba1 t h tak5 on  
special duties-- 9 a ^w1 !y are         
speciali/s4 ,! amoeba is ,jack ( all    
trades & a free lance2 ! protective     
epid]mal cell1 ! curr5t-mak+ ciliat$    
cell1 ! bile or urea-mak+ secretory     
cell1 is ma/] ( "o trade1 & a soldi] 9 a
 va/ & wond]fully organiz$ ho/4 ,we w n[
 consid] our second k9d ( cell 9 ?is    
organization1 ! cell ( :i* ! especial   
aim is ! build+ r\nd x ( a tissue4      
,section #fd4 ,! simple/ v>iety 9 ?is   
gr\p is hyal9e 7i4e4 glassy7 c>tilage   
7gri/le74 ,9 ?is ! =mative cells 7!     
c>tilage corpuscles7 are enjelli$ 9 a   
cle> /ructureless matrix 7,figure       
,,xii471 consi/+ entirely ( organic     
comp\nds accumulat$ by _! activity4     
,imm$iately r\nd ! cell lies a capsule (
 new] mat]ial4 ,"s ( ! cells h rec5tly  
divid$ 7#a72 o!rs h done s less rec5tly1
 & !re has be5 "t = ! int]polation (    
matrix1 z at #b4 ,9 ?is way ! tissue    
gr[s & is repair$4 ,a ?9 lay] (         
connective tissue 7see bel[71 !         

p]i*ondrium1 clo!s ! c>tilag9\s         
/ructure4   ,section #fe4 ,connective   
tissue 7,figure ,,xiii7 is a g5]al "n = 
a gr\p ( tissues ( v v>iable "*4 ,x is  
usually describ$ z consi/+ typically 9 !
 mammals ( ?ree *ief elem5ts felt$      
toge!r2 ( comp>atively unmodifi$        
corpuscles 7c4c471 m or less amoeboid1 &
 ( fibres :i* are elongat$1 alt]$1 &    
di/ort$ cells4 ,! fibres are ( two k9ds3
 yell[1 bran*+1 & highly ela/ic         
7y4e4f471 9 consequ5ce ( :i* !y fall    
into s9u\s l9es 9 a prep>ation1 & :ite &
 inela/ic ones 7w4i4f471 ly+ 9 p>allel  
bundles4 ,:]e ! latt] elem5t is entirely
 dom9ant1 ! connective tissue is t5don1 
f\nd especially at ! po9t ( atta*m5t (  
muscles to ! p>ts !y "w4 ,"s ela/ic     
ligam5ts are almo/ purely yell[ fibr\s  
tissue4 ,a loose int]weav+ ( ! ?ree     
elem5ts is areol> tissue1 ! *ief fabric 
( mes5t]y1 membrane1 & ! d]mis 7b5ea? ! 
epid]mis74 ,) muscle x is ! mat]ial ( ! 
walls ( ! alim5t>y canal & bloodvessels1
 & g5]ally x ent]s into1 b9ds toge!r1 & 

holds 9 place o!r tissue4 ,! connective 
tissue ( fi%es displays ! diff]5tiation 
( fibres 9 a f> less di/9ct mann]4      
,section #ff4 ,?r\gh connective tissues 
w&] ! phagocytes1 cells t are difficult 
to di/+ui%1 if really di/9ct1 f ! :ite  
blood corpuscles4 ,^! cells possess a   
rem>kable fre$om2 !y %[ an initiative ( 
_! own1 & seem end[$ ) a subord9ate     
individuality4 ,!y occur 9 great numb]s 
9 a tissue call$1 botryoidal tissue     
7,figure ,,xiv471 :i* occurs especially 
9 masses & pat*es along ! c\rse ( !     
alim5t>y canal1 9 its walls4 ,! tonsils1
 swell+s on ei!r side ( ! ?roat1 are su*
 masses1 & aggregates occur z visible   
pat*es1 ! ,pey]'s pat*es1 on ! ileum4 ,x
 also con/itutes ! mass ( ! v]mi=m      
app5dix & ! wall ( ! sacculus rotundus2 
& 9 ! "y animal ! ?ymus gl&1 v5tral to !
 he>t1 & less entirely1 ! ?yroid gl&1   
v5tral to ! l>ynx1 are simil> /ructures1
 :i* are r$uc$ or disappe> z developm5t 
proce$s4 ,x is evid5t t 9 ^! two latt]  
cases ! t]m gl& is some:at ( a misnom]4 

,! matrix ( botryoidal tissue is a      
network ( /ret*$ & holl[$ connective    
tissue cells-- x is n a secretion1 z    
c>tilage matrix appe>s to be4 ,dur+     
dige/ion1 ! phagocytes pr[l into !      
inte/9e1 & +e/ & dev\r bact]ia1 t might 
o!rwise give rise to disease4 ,9        
inflammation1 we may note "h1 !y conv]ge
 f all directions ^u ! po9t w\nd$ or    
irritat$4 ,!y appe> to be ! active ag5ts
 9 all processes ( absorption 7see      
o/eocla/s "u bone71 & = in/ance1 migrate
 into & dev\r ! tissue ( ! tadpole's    
tail1 dur+ its metamorphosis to ! adult 
frog4   ,section #fg4 ,)9 ! connective  
tissue cells fat drops may be =m$1 z 9  
,figure ,,xv4 ,adipose tissue is simply 
connective tissue load$ ) fat-di/5d$    
cells4 ,! tissue is1 ( c\rse1 a /ore =m 
( hydro-c>bon 7,section #ag7 provid$    
aga9/ ! possible misadv5ture ( />vation4
 ,) ! exception ( "s hyb]nat+ animals1  
su* /ore =ms w\ld seem to be ( accid5tal
 importance only among animals1 :]eas   
among plants !y are ( inv>iable &       

necess>y occurr5ce4   ,section #fh4 ,we 
n[ come to ,bone1 a tissue conf9$ to !  
v]tebrata1 & typically %[n only 9 !     
high] types4 ,z we desc5d 9 ! scale f   
birds & mammals to liz>ds1 amphibia     
7frogs & toads7 & fi%1 we f9d c>tilage  
cont9ually m important1 & ! bony        
con/itu5t ( ! skeleton correspond+ly    
less s4 ,9 su* a type z ! dog-fi%1 !    
skeleton is entirely c>tilag9\s1 bone   
only occurs 9 connection ) ! animal's   
scales2 x mu/ h be5 9 connection )      
scales t bone fir/ appe>$ 9 ! v]tebrate 
sub-k+dom4 ,9 ! frog we h a c>tilag9\s  
skeleton ov]laid by num]\s bony scutes  
7%ield-l plates7 :i*1 :5 ! /ud5t comes  
to /udy t type1 he w p]ceive are        
equival5t to ! bony p>ts ( su* scales z 
occur 9 ! dog-fi%1 sunk inw>d1 & plat+  
ov] ! c>tilage2 & 9 ! frog ! c>tilage   
also is itself1 9 a few places1 replac$ 
by bony tissue4 ,9 ! adult rabbit ^! two
 k9ds ( bone1 ! bone ov]ly+ :at 0       
orig9ally c>tilage 7membrane bone71 & ! 
bone replac+ ! c>tilage 7c>tilage bone7 

h1 betwe5 !m1 practically sup]s$$ !     
c>tilage altoge!r4 ,! /ructure ( ! mo/  
*>act]i/ic k9d ( bone w be und]/ood by  
ref]5ce to ,figure ,,xvi4 ,x is a       
simplifi$ diagram ( ! transv]se section 
( su* a bone z ! ?igh bone4 ,m4,c4 is ! 
c5tral m>r[ cavity1 ,h4v41 ,h4v4 are    
cross sections ( small bloodvessels1 !  
,hav]sian vessels runn+ m or less       
longitud9ally ?r\gh1 ! bone 9 canals1 ! 
,hav]sian canals4 ,arrang$ r\nd ^!      
vessels are circles ( ! =mative elem5ts1
 ! bone corpuscles or o/eobla/s 7b4c47  
ea* emb$d$ 9 bony matrix 9 a little b$1 
! lacuna1 & communicat+ "o ) ano!r by   
f9e processes ?r\gh canaliculi 9 !      
matrix1 :i* processes are only to be se5
 cle>ly 9 decalcifi$ bone 7,see ,section
 #gj74 ,! o/eobla/s are arrang$ 9       
conc5tric s]ies1 & ! matrix is !re=e 9  
conc5tric lay]s1 or lamellae 7c4l474    
,)\t & )9 ! zone ( ,hav]sian sy/ems are 
7o4l4 & i4l471 ! out] & inn] lamellae4  
,! bone is surr\nd$ by connective       
tissue1 ! p]io/eum4 ,9 addition to ?is  

compact bone1 !re is a light] & loos]   
v>iety 9 :i* spicules & b>s ( bony      
tissue are loosely int]wov54 ,_m flat   
bones1 ! bones ( ! skull1 = in/ance1    
consi/ ( ?is spongy bone1 plat$ 7z an   
electro spoon is plat$7 ) compact bone4 
,section #fi4 ,among ! bony b>s &       
spicules ( spongy bone occurs ! r$      
m>r[-- :i* mu/ n be confus$ ) ! yell[   
m>r[1 ! fatty sub/ance 9 ! c5tral cavity
 ( long bones4 ,9 ?is r$ m>r[ are num]\s
 l>ge col\rless cells1 :i* appe> to =m  
)9 _! sub/ance & !n lib]ate r$ blood    
corpuscles4 ,?is occurs especially 9 !  
spongy bone )9 ! ribs4   ,section #gj4  
,! matrix ( bone diff]s f t ( c>tilage  
or ( mo/ o!r tissues 9 consi/+ *iefly ( 
inorganic salts4 ,! *ief ( ^! is calcium
 phosphate1 ) :i* mu* small] quantities 
( calcium c>bonate1 & magnesium         
phosphate & c>bonate occur4 ,^!         
inorganic salts c be remov$ by imm]sion 
( ! bone 9 weak hydro*loric acid1 & a   
flexible network ( connect+ tissue1     
,hav]sian vessels1 bone corpuscles1 & _!

 processes rema9s4 ,?is is decalcifi$   
bone allud$ to above4   ,section #ga4 ,9
 ! v "y rabbit1 ! limb bones1 v]tebral  
column1 & _m ( ! skull bones are simply 
plates & b>s ( c>tilage2 ! future       
membrane bones1 h[ev] are plann$ out 9  
connective tissue4 ,! developm5t ( !    
latt] is simple1 ! connective tissue    
corpuscles function+ by a simple *ange (
 product z o/eobla/4 ,! developm5t ( !  
c>tilage bones1 h[ev]1 is m complicat$4 
,figure ,,xvii41 repres5ts1 9 a         
diagrammatic way1 ! /ages 9 ! conv]sion 
( a c>tilag9\s b> to bone4 ,to beg9 )1 !
 previ\sly sporadically-arrang$ 7scatt]$
 anyh[7 corpuscles 7u4c4c47 are ga!r$   
into gr\ps 9 s+le file1 or 9 o!r words1 
into column> gr\ps 7z at c4c474 ,!      
matrix becomes cl\d$ ) inorganic salts (
 lime1 & x is !n said to be calcifi$4   
,?is calcifi$ c>tilage !n und]goes      
absorption-- x mu/ n be imag9$ = a mom5t
 t bone is calcifi$ c>tilage4           
,simultane\s ) ! =mation ( ! cavities   
7s47 due to ?is absorption1 connective  

tissue 7p4c4i47 f ! surr\nd+ p]i*ondrium
 7p4c47 gr[s into ! ossify+99 b>4 ,x is 
f ?is connective tissue t ! o/eobla/s   
7o4b47 arise1 & bone is built up4       
,?r\gh\t life a bone is cont9ually be+  
absorb$ & re=m$ by ! activity ( !       
o/eobla/s4 ,an o/eobla/ engag$ 9 !      
absorption in/ead ( ! =mation ( bone is 
call$ an o/eocla/4  99 ,! =mation ( bone
 is call$ ossification4 ,to ossify is to
 become bony4   ,section #gb4 ,! great  
?+ to notice ab\t ?is is t c>tilage does
 n become bone1 b is eat5 into & ou/$ by
 x2 ! o/eobla/s & o/eocla/s replace     
entirely ! c>tilage corpuscles1 & are n 
d]iv$ f !m4   ,section #gc4 ,we may     
m5tion "h ! /ructure ( ! sple5 7,figure 
#a1 ,%eet #a74 ,x consi/s ( a connective
 tissue & muscul> coat+1 ) an int]nal   
s(t matrix mu* resembl+ botryoidal      
tissue1 trav]s$ by fibr\s trabeculne 7  
beams1 planks7 conta9+ blood-vessels1 & 
! :ole organ is gorg$ ) blood1          
p>ticul>ly aft] meals4 ,! consid]ation (
 its function ! /ud5t may conv5i5tly    

def] = ! pres5t4   ,section #gd4 ,"h    
also1 we may notice ! lymphatics1 a     
s]ies ( small vessels :i* return !      
ov]fl[ ( ! blood s]um f ! capill>ies1 9 
! nutrition ( ! tissues 9 all p>ts ( !  
body1 to ! ?oracic duct 7see ,section   
#cf71 & ! g5]al circulation4 ,at        
int]vals _! c\rse is int]rupt$ by gl&-l 
dilatations1 ! lymphatic gl&s1 9 :i*    
masses ( rapidly divid+ & gr[+          
7prolif]at+7 cells occur1 ( :i*1        
d\btless1 _m are deta*$ & become1 fir/  
lymph corpuscles1 &1 :5 !y rea* ! ve9s1 
:ite blood corpuscles4    #e4 ,!        
,skeleton  ,section #ge4 ,we are n[ 9 a 
position to /udy ! rabbit's skeleton4   
,we /rongly recomm5d ! /ud5t to d ?is ) 
! actual bones at h&-- !y may be cle>$ v
 easily 9 a well-boil$ rabbit4 ,?is     
recomm5dation may appe> sup]flu\s to "s 
read]s1 b1 z a matt] ( fact1 ! m>k$     
proclivity ( ! av]age s*oolma/] = m]e   
book-"w has put su* a /amp on /udy1 t1 9
 n9e cases out ( t51 a /ud5t1 unless he 
is expressly in/ruct$ to ! contr>y1 w g 

to ! tortu\s1 & possibly inexact1       
descriptions ( a book = a k ( ?+s t lie 
at 8 v f+]-tips4 ,we h n writt51 ?is    
*apt] to give a complete k ( ! skeleton1
 b simply z an aid 9 ! actual exam9ation
 ( ! bones4   ,section #gf4 ,we may take
 ! skeleton "u five head+s4 ,!re is !   
c5tral axis1 ! *a9 ( little bones1 !    
v]tebrae1 ?read$ on ! sp9al cord 7see   
,figure #a & ,section #a72 ! ?orax1 !   
box enclos$ by ribs & /]num2 ! =e-limb &
 bones connect$ ) x 7pectoral girdle &  
limb71 & ! h9d-limb & bones connect$ ) x
 7pelvic girdle74 ,f9ally !re is !      
skull1 b foll[+ ! ,london ,univ]sity    
syllabus1 we %all sub/itute ! skull ( ! 
dog = ( t ( ! rabbit1 z m typically     
mammalian 7,section #d74   ,section #gg4
 ,9 ,section #c 7:i* ! /ud5t %\ld ref]  
to7 we h a division ( ! v]tebrae into   
f\r v>ieties4 ,( ^! mo/ repres5tative is
 ! ?oracic4 ,a ?oracic v]tebra 7,figure 
#d1 ,%eet #e1 ,t4,v47 consi/s ( a c5tral
 bony mass1 ! body or c5trum 7b471 f :i*
 !re arises dorsally an ar*1 ! neural   

ar* 7n4a471 complet$ by a key/one1 !    
neural sp9e 7n4s472 & com+ (f lat]ally f
 ! ar* is ! transv]se process 7tr4p474  
,look+ at ! v]tebra sideways1 we see t !
 ar* is not*$1 = ! exit ( n]ves4 ,jo9t$ 
to ! ?oracic v]tebrae on ei!r side are !
 ribs 7r474 ,ea* rib has a process1 !   
tub]culum1 go+ up to articulate ) !     
transv]se process1 & "o1 ! capitulum    
articulat+ betwe5 ! bodies ( two        
contigu\s v]tebrae4 ,! facets = !       
articulation ( ! capitulum are indicat$ 
9 ! side view by %ad+4 ,at ei!r end ( ! 
body ( a v]tebra ( a "y rabbit are bony 
caps1 ! epiphyses 7ep471 sep>at$ f !    
body by a plane ( unossifi$ c>tilage    
7indicat$1 by ! dots74 ,^! epiphyses to 
! v]tebral bodies occur only among      
mammals1 & are ev5 abs5t 9 "s cases )9 !
 class4 ,9 ! adult rabbit !y h ossifi$  
cont9u\sly ) ! re/ ( ! body4   ,section 
#gh4 ,a c]vical v]tebra 7,c4,v47 seems1 
^u cursory inspection1 to h no rib4 ,!  
transv]se processes diff] f ^? ( ?oracic
 s]ies 9 hav+ a p]=ation1 ! v]tebr>t]ial

 canal1 ?r\gh :i* ! v]tebral art]y runs 
up ! neck4 ,a /udy ( ! developm5t ( ^!  
bones %[s t ! "p m>k$ f4r4 ossifies     
sep>ately f ! re/ ( ! transv]se process2
 & ! =m ( ! equival5t /ructures 9 c]ta9 
peculi> l[] mammals & 9 reptiles leaves 
no d\bt t f4r4 is really an abbreviat$  
rib2 fus$ up ) ! transv]se process &    
body4 ,! two ant]ior c]vical v]tebrae   
are peculi>4 ,! fir/ 7at47 is call$ !   
,atlas-- ! figure %[s ! ant]ior view-- &
 has great articul> faces = ! condyles  
7,section #hf7 ( ! skull1 & a defici5t  
c5trum4 ,! next is ! axis1 & x is       
di/+ui%$ by an odontoid peg 7od4p471 :i*
 fits into ! space :]e ! body ( ! atlas 
is defici5t4 ,9 developm5t ! c5trum ( ! 
axis ossifies f "o c5tre1 & ! odontoid1 
peg f ano!r1 :i* at t "t occupies !     
position ( c5trum ( ! atlas4 ,s t x w\ld
 seem t ! atlas is a v]tebra m9us a     
c5trum1 & ! axis is a v]tebra plus a    
c5trum1 add$ at ! exp5se ( ! atlas4     
,section #gi4 ,! lumb> v]tebrae 7l4v47  
are l>g]1 & h cleft transv]se processes1

 ea* giv+ rise to an asc5d+ limb1 !     
metapophyses1 & a desc5d+ "o4 ,! latt]  
7g5]ally spok5 ( z ! transv]se          
processes7 po9t /eeply d[nw>d1 & are    
consid]ably long] ?an ^? ( ?oracic      
s]ies4 ,! sacral v]tebrae 7s4v47 h great
 flatt5$ transv]se propcesses =         
articulation ) ! ilia4 ,! caudal        
v]tebrae 7c4v47 are gradually r$uc$ to !
 m]e elongat$ c5tra1 z we proce$1 t[>ds 
! tip ( ! tail4   ,section #hj4 ,all !  
v]tebrae jo9 ) _! adjac5t fell[s ?r\gh !
 int]m$iation ( c]ta9 int]v]tebral pads1
 & also articulate by small processes at
 ei!r end at ! upp] side ( ! ar*1 !     
zygapophyses4 ,! normals to ! poli%$    
facets ( ^! po9t1 9 ! case ( ! ant]ior  
zygapophyses1 up & 9 7mnemonic3         
ant-up-971 & 9 ! case ( ! po/]ior1 d[n &
 out4 ,! /ud5t %\ld make ?is1 & ! o!r   
features ( v]tebrae1 out ^u actual      
specim5s4   ,section #ha4 ,! ?orax is   
b\nd$ dorsally by ! v]tebral column1 &  
v5trally by ! /]num4 ,! /]num consi/s ( 
segm5ts1 ! /]nebrae 7/472 ant]iorly !re 

is a bony manubrium 7mb471 po/]iorly a  
?9 c>tilag9\s plate1 ! xiphi/]num 7xi474
 ,sev5 pairs ( ribs articulate by       
c>tilag9\s ends 7/]nal ribs7 ) ! /]num  
directly1 z indicat$ 9 ! figure2 five   
7false7 ribs are jo9$1 to ea* o!r & to !
 sev5?1 & n to ! /]num directly4 ,! la/ 
f\r ribs h no tub]culum 7,section #gg74 
,section #hb4 ,! =e-limb 7pectoral limb7
 consi/s ( an upp] arm bone1 ! hum]us   
7hum47 ! di/al end ( :i* is deeply      
excavat$ by ! olecranon fossa 7o4f47 z  
indicat$ by ! dott$ l9es2 ( two bones1 !
 ulna 7u47 & radius 7r47 :i* are firmly 
b\nd by ligam5t 9 ! position ( ! figure 
7i4e41 ) ! palm ( ! h& d[nw>d1 prone72 (
 a numb] ( small bones 7c>palia71 !     
c>pus 7c472 ( a s]ies ( metac>pals      
7mc472 & ( ?ree digits 7 f+]s7 ea*1     
except ! fir/1 or pollex1 ( ?ree small  
bones-- ! phalanges1 only ! proximal (  
:i* appe> 9 ! figure4 ,! ulna has a     
hook-l head1 ! olecranon 7o47 :i*       
di/+ui%es x easily f ! di/ally ?ick5$   
radius4 ,! limb is atta*$ to ! body     

?r\gh ! int]m$iation ( ! %\ld]-blade    
7scapula1 sc47 a flatt5$ bone ) a m$ian 
ext]nal ridge ) a hook-l t]m9ation1 !   
acromion 7acr474 ,!re is also a process 
ov]hang+ ! gl5oid cavity 7g47 :]e9 !    
hum]us articulates1 :i* process is call$
 coracoid 7co472 x is ossifi$ f two     
sep>ate c5tres1 & repres5ts a v         
consid]able bone 9 ! bird1 reptile1 &   
frog4 ,along ! dorsal edge ( ! scapula (
 ! rabbit is unossifi$ c>tilage1 :i* is 
call$ ! supra-scapula 7s4sc474 ,9 man   
!re runs f ! acromion to ! manubrium ( !
 /]num a bone1 ! coll>-bone or clavicle4
 ,?is is repres5t$ by a v imp]fectly    
ossifi$ rudim5t 9 ! rabbit4 ,! scapula &
 clavicle1 ! bones ( ! body connect$ ) !
 =e-limb1 are frequ5tly /yl$ ! pectoral 
girdle1 or %\ld]-girdle2 ?is "n ( girdle
 w appe> less ( a misnom] :5 l[]        
v]tebrate types are /udi$4   ,section   
#hc4 ,! h9d limb & its body bones--     
pelvic limb & girdle-- are %[n 9 ,figure
 #b4 ,! limb skeleton corresponds       
closely ) t ( ! =e-limb4 ,! femur 7fe47 

answ]s to ! hum]us1 & is to be di/+ui%$ 
f x by ! great] di/9ctness ( its        
proximal head 7hd47 & by ! abs5ce ( an  
olecranon fossa f its di/al end4 ,!     
tibia 7ti  ! radius7 is fus$ = ! di/al  
half ( its l5g? ) ! fibula 7fb4  ulna74 
,a t>sus 7t>salia7 equals ! c>pus499    
,two ( ! proximal t>salia may be not$3  
"o work+ l a pulley "u ! tibia1 is !    
a/ragalus 7z472 "o =m+ ! bony support ( 
! heel1 is ! calcaneum 7ca474 ,!re is a 
s]ies ( metat>sals1 & !n come f\r digits
 ( ?ree phalanges ea*4  99 ,su* a       
resemblance z exi/s betwe5 "o v]tebra & 
ano!r 9 ! rabbit1 or betwe5 ! hum]us & !
 femur1 is call$ s]ial homology2 ! two  
?+s correspond ) ea* o!r to ! ext5t (   
imp]fect r$uplication4 ,homology simply 
is commonly us$ to indicate !           
resemblance betwe5 any two /ructures 9  
diff]5t animals1 9 orig9 & position z   
reg>ds o!r p>ts4 ,?us ! he>t ( ! rabbit 
& ( ! frog are homolog\s /ructures1     
correspond+ 9 position1 & resembl+ ea*  
o!r mu* z two memory sket*es ( "o       

picture might d4   ,section #hd4 ,!     
pelvic girdle diff]s f ! pectoral 9 mo/ 
l& v]tebrata 9 be+ articulat$ ) !       
v]tebral column4 ,?is diff]5ce does n   
exi/ 9 fi%es4 ,x consi/ 9 ! rabbit ( f\r
 bones2 ! ilium 7i471 ! is*ium 7is471 ! 
pubis 7pb471 & ! small cotyloid bone-- !
 fir/ two & ! latt] "o meet+ 9 !        
acetabul> fossa 7ac47 9 :i* ! head ( !  
femur works4 ,! pubes & is*ia are fus$  
along ! mid-v5tral l9e4 ,_m morphologi/s
 reg>d1 ! ilium z equival5t to1 t is1   
/rictly correspond+ 9 its relation1 to !
 scapula1 ! pubis to ! c>tilag9\s       
sub/ratum ( ! clavicle1 & ! is*ium to ! 
coracoid4   ,section #he4 ,^! bones w be
 /udi$ at ! greate/ advantage :5        
dissect$ out f a boil$ rabbit4 ,prep>$ &
 wir$ skeletons1 dis>ticulat$ skeletons1
 plates ( figures1 & writt5 descriptions
 are 9 succession m t$i\s & less        
satisfactory ways to a real             
compreh5sion1 ( ?is matt]4 ,?is *apt]   
directs ! /ud5t's att5tion to ! mo/     
important po9ts 9 ! /udy ( ! skeleton1 b

 x is 9 no way int5d$ to mitigate !     
necessity ( practical "w4 ,x is a guide 
simply4   ,section #hf4 ,! mammalian    
skull w be bett] und]/ood aft] ! /udy ( 
t ( "s l[] v]tebrate4 ,we %all describe 
its ma9 features n[1 b _! mean+ w be mu*
 cle>] aft] ! l[] type is read4 ,our    
figures are ( ,canis4 ,9 section        
7,figure ,,vi41 ,%eet #f71 we p]ceive a 
bra9 case 7cranium7 op5+ beh9d by a l>ge
 ap]ture1 ! =am5 magnum 7,f4,m474 ,9    
front ( ?is is an ext5sive passage1 !   
nasal passage 7,e4,n4 to ,p4,n47 :i* is 
divid$ f ! m\? by a bony floor1 !       
palate1 & :i* op5s into ! ph>ynx beh9d  
at ! po/]ior n>es 7,p4,n47 & to !       
ext]ior by ! ant]ior or ext]nal n>es    
7,e4,n474 ,x is divid$ into "r & left   
passages by a middle p>tition1 ! nasal  
septum4 ,outside ! skull1 on its w+s1 is
 a flask-l bone1 ! bulla tympani 7b4 9  
,figures #b & #c71 protect+ ! middle e>1
 & f above ?is !re passes an ar*1 ! *eek
 bone 7ju4 9 ,figures #a1 #b1 & #c71 to 
! upp] jaw1 =m+ 9 front ! bony l[]      

protection ( ! cavity conta9+ ! eye1 !  
orbit4 ,! *eek ar*1 nasal passage1 &    
jaws1 =m collectively ! facial app>atus1
 z di/+ui%$ f ! cranium1 & ! :ole skull 
is sometimes ref]r$ to z1 !             
cranio-facial app>atus4 ,two em95ces =  
articulation ) ! atlas v]tebra1 !       
condyles 7c471 lie "o on ea* side ( !   
l[] b\nd>y ( ! =am5 magnum4   ,section  
#hg4 ,! floor ( ! cranium consi/s ( a   
s]ies ( c>tilage bones1 ! basi-occipital
 7b4o471 basi-sph5oid 7b4sp471          
pre-sph5oid 7p4sp471 & 9 front1 ! e?moid
 7e?471 :i* s5ds d[n a m$ian plate1 n   
%[n1 9 ! figure1 to =m ! nasal septum   
betwe5 "r & left nasal passages4 ,l     
ext5d$ w+s on ei!r side ( !             
basi-occipital are ! ex-occipital 7e4o47
 7! bone is m>k$ 9 ,figure #d1 b !      
lett]s are a little obscur$ by %ad+74   
,simil>ly ! ali-sph5oids 7a4s471 are w+s
 to ! basi-1 & ! orbito-sph5oids 7o4s471
 to ! pre-sph5oid bone 7p4sp474 ,betwe5 
! ex-occipital & ali-sph5oid !re is w$g$
 9 a bone1 ! p]iotic 7p4o47 conta9+ !   

int]nal e> 7,section #aae74 ,above !    
=am5 magnum ! m$ian supra-occipital bone
 completes :at is call$ ! occipital ar*4
 ,a pair ( p>ietals 7pa47 come above !  
ali-sph5oids1 & a pair ( frontals 7f47  
above ! orbito-sph5oids4 ,at ! side !   
bra9 case is /ill incomplete1 & "h !    
aquamosal 7sq47 ent]s into its wall4 ,9 
! ext]nal view 7,figure #c7 ! bulla     
hides ! p]iotic bone f )\t4 ,! /ud5t    
%\ld exam9e all f\r figures = ^! bones  
be=e proce$+4   ,section #hh4 ,! out]   
edge ( ! upp] jaw & ! *eek ar* are made 
up ( ?ree pair$ bones4 ,fir/ comes !    
premaxilla 7p4m47 7n p4m4#a or p4m4#d71 
conta9+ 9 ! dog1 ! ?ree incisors ( ei!r 
side4 ,!n comes ! maxilla1 be>+ ! re/ ( 
! tee?499 ,! jugal or mal> 7ju47 rea*es 
ov] f ! maxilla to meet a zygomatic     
process 7 connect+ outgr[?7 7z4p47 ( !  
squamosal bone4  99 ,9 ! dog a sabre-l  
can9e 7c471 f\r premol>s 7p4m4#a &      
p4m4#d7 & two mol>s 7m4#a & m4#b74      
,section #hi4 ,9 ! "u view ( ! skull    
7,figure #b7 x w be se5 t ! maxilla s5ds

 9 a plate to =m ! front "p ( ! h>d     
palate4 ,beh9d1 ! h>d palate is complet$
 by ! pair ( palat9e bones 7pal471 :i*  
conceal mu* ( ! pre- & orbito-sph5oid 9 
! v5tral view1 & :i* run back z ridges  
to t]m9ate 9 two small angul> bones1 !  
pt]ygoids 7pt47 :i* we %all f9d repres5t
 mu* m important /ructures 9 ! l[]      
v]tebrata4   ,section #ij4 ,!           
pre-maxillae & maxillae b\nd ! sides ( !
 nasal passage1 & x is complet$ above by
 a pair ( spl9ts1 ! nasals4 ,along !    
floor ( ! nasal passage1 on ! middle    
l9e1 lies a spl9t ( bone =m$ by !       
coalesc5ce ( two halves4 ,x embraces 9 a
 ,v-l groove ! mese?moid 7nasal septum7 
above1 & lies on ! palate4     ,l9es f  
,fir/ ,edition only4    -,its position  
is indicat$ by a heavy black l9e 9 #d1 &
 x is    call$1 ! vom] bone 7vo474-     
,l9es f ,second ,edition only4    ,9 !  
frog x is repres5t$ by two lat]ally     
situat$ bones4    ,?is is ! vom] bone   
7vo474  ,! nasal passages are p>tially  
block$ by foliat$ bony outgr[?s1 f !    

inn] aspect ( _! walls1 :i* 9 life are  
cov]$ ) muc\s membrane1 & increase !    
surface s5sitive to smell4 ,! e?moid    
ends 9 ! e?mo-turb9al 7e4t472 ! nasal1 !
 naso-turb9al 7n4t472 & ! maxilla1 !    
maxillo-turb9al 7m4t474 ,9 ! ant]ior    
corn] ( ! orbit !re is a bone1 !        
la*rymal 7lc4 ,figure #a71 :i* is hidd5 
by ! maxilla 9 ! side view ( ! skull4   
,section #ia4 ,! l[] jaw 7m&ible7 is "o 
cont9u\s bone 9 ! mammal4 ,?ree incisors
 bite aga9/ ! ?ree ( ! upp] jaw4 ,!n    
comes a can9e1 f\r premol>s1 & ?ree     
mol>s1 ! fir/ ( :i* is blade-l          
7sectorial too?71 & bites aga9/ ! simil>
 sectorial too? 7la/ premol>7 ( ! upp]  
jaw4 ,! ?ird mol> is small4 ,!          
arrangem5t ( too? is indicat$ 9 ! foll[+
 d5tal =mula3-- ,i4 #c4c_/c4c1 ,c4      
#a4a_/a4a1 ,p4,m4 #d4d_/d4d1 ,m4        
#b4b_/c4c   ,section #ib4 ,atta*$ j     
beh9d ! bulla above1 & pass+ r\nd on    
ei!r side ( ! ?roat to meet at ! base ( 
! tongue1 is ! hyoid app>atus 7,figure  
#f74 ,! /ylohyal 7s4h471 epihyal 7e4h471

 & c]atohyal 7c4h47 =m ! ant]ior cornu (
 ! hyoid4 ,! body ( ! hyoid 7b4h47 =ms a
 basis = ! tongue4 ,! po/]ior coruna    
7t4h47 ( ! hyoid are also call$ !       
?yrohyals4   ,section #ic4 ,! foll[+    
table pres5ts ^! bones 9 some?+ l _!    
relative positions4 ,a clos]            
approximation to ! /ate ( ! case w be   
rea*$ if ! /ud5t w imag9e ! maxilla     
rais$ up s z to ov]lie & hide ! palat9e 
& presph5oid1 ! squamosal simil>ly      
ov]ly+ ! p]iotic bone1 & ! jugal rea*+  
betwe5 !m4 ,membrane bones are di/+ui%$ 
by capital lett]s4     -,cranium        
-,nasal 7pair$71 ,e?moid ,bone 7m$ian71 
-,vom]       -,frontal 7pair$71         
-,la*rymal 7pair$71 ,orbito-sph5oid     
7pair$71       ,pre-sph5oid 7m$ian71    
,eye       -,p>ietal 7,pair$71          
,ali-sph5oid 7pair$71 ,basi-sph5oid     
7m$ian7991       ,p]iotic ,bone 7pair$7 
-,bulla 7pair$7       ,supra-occipital  
7m$ian71 ,ex-occipital 7pair$71         
,basi-occipital          7m$ian7        
-,upp] ,jaw        -,pre-,maxilla       

7pair$7       ,palat9e 7pair$7          
,pt]ygoid 7pair$7     -,l[] ,jaw        
-,maxilla 7pair$7       -,jugal 7pair$7 
-,squamosal 7pair$7     99,9 ?is table !
 small bones ( ! e> are simply indicat$ 
by an    a/]isk4   ,section #id4 ,hidd5 
by ! bulla1 & j ext]nal to ! p]iotic    
bone1 are ! auditory ossicles1 ! incus1 
malleus1 os orbicul>e1 & /apes4 ,^! w be
 m explicitly treat$ :5 we discuss ! e>4
   ,section #ie4 ,:5 we come to ! /udy (
 ! n]ves1 we %all rev]t to ! skull1 &   
treat ( its p]=ations4 ,! /ud5t %\ld n  
fail1 be=e proce$+1 to copy & recopy our
 figures1 & to make himself q famili> ) 
!m1 & he %\ld also obta9 & h&le an      
actual skull4 ,= all practical purposes 
! skull ( a %eep or cat w be almo/ z    
useful z t ( ! dog4    #f4 ,muscle &    
,n]ve  ,section #if4 ,we h1 9 !         
skeleton1 a complicat$ app>atus ( p>ts  
h+$ & movable ^u "o ano!r2 ! ag5t mov+  
^! p>ts is ! same ag5t t we f9d 9 ! he>t
 walls propell+ ! blood ?r\gh !         
circulation1 9 ! alim5t>y canal squeez+ 

! food along its c\rse1 & univ]sally 9 !
 body :]e motion occurs1 except 9 ! case
 ( ! creep+ phagocytes1 & ! cili>y wav+ 
( ciliat$ epi!lium4 ,?is ag5t is muscle4
 ,we h1 9 muscul> tissue1 a v wide      
dep>ture f ! /ructure ( ! primordial    
cell2 to use a common biological        
expression1 a v great am\nt (           
modification 7 diff]5tiation74 ,%eet #g 
repres5ts ! simpl] k9d ( muscul> tissue1
 un/riat$ muscle1 9 :i* ! cell "* is    
/ill fairly obvi\s4 ,! cells are fusi=m 
7sp9dle-%ap$71 h a di/9ct nucleus & fa9t
 longitud9al /riations 7/riations along 
_! l5g?71 b no transv]se /riations4     
,section #ig4 ,9 /riat$ muscle ext5sive 
modifications mask ! cell "*4 ,"u a     
#a_/d in* objective1 transv]se /riations
 ( ! fibres are also di/9ctly visible1 &
 "u a mu* high] p[] we disc]n 9 a fibre 
7,%eet #g7 transv]se columns ( rod-l    
s>c\s elem5ts 7s4e471 ! columns sep>at$ 
by l9es ( dots1 ! membranes ( ,krause   
7k4m471 & nuclei 7n471 flatt5$ & sep>at$
 into portions1 & ly+1 9 "s cases1 close

 to ! s>colemma 7sc47 ! connective      
tissue enclos+ ! fibre1 9 o!rs scatt]$  
?r\gh\t ! sub/ance ( ! fibre4 ,! figure 
%[s ! fibre ruptur$1 9 ord] to display !
 s>colemma2 e4p4 is ! end plate ( a n]ve
 7n4v471 & fb4 are ! fibrillae into :i* 
a fibre may be teas$4   ,section #ih4 ,9
 ! he>t we h an int]m$iate k9d ( muscle 
c>diac muscle 7,figure #b71 9 :i* !     
muscle fibres bran*2 !re is app>5tly no 
s>colemma1 & ! undivid$ nuclei lie 9 !  
c5tre ( ! cell4   ,section #ii4         
,un/riat$ muscle is sometimes call$     
involunt>y1 & /riat$1 volunt>y muscle2 b
 !re is really n ! connexion ) ! w t ^! 
t]ms sugge/4 ,we h j m5tion$ t !        
he>t-muscle is /riat$1 b :o c alt] !    
beat+ ( ! he>t by =ce ( w8 ,& ! /riat$  
muscles ( ! limbs p]=m1 endless         
involunt>y acts4 ,x w\ld seem t un/riat$
 muscle contracts sl[ly1 & we f9d x     
especially among ! visc]a2 9 ! inte/9e =
 in/ance1 :]e x controls t p]i/altic    
movem5t :i* pu%es ! food =w>d4 ,volunt>y
 muscle1 on ! o!r h&1 has a %>p         

contraction4 ,! muscle ( ! sl[-mov+     
snails1 slugs1 & mussels is un/riat$2   
all ! muscle ( ! active insects &       
cru/acea 7crabs1 lob/]s1 & crayfi%7 is  
/riat$4 ,/ill if ! /ud5t be>s !         
exception ( ! he>t 9 m9d1 & consid]s    
muscles z volunt>y t 8 w c rea*1 ! t]ms 
volunt>y & involunt>y w s]ve to give him
 an idea ( ! di/ribution ( ^! two types 
( muscle 9 8 own body1 & 9 t ( ! rabbit4
   ,section #ajj4 ,muscul> contraction1 
& g5]ally all activity 9 ! body is      
accompani$ by kataboly4 ,! m$ium by :i* 
^! katabolic *anges are set go+ &       
controll$ is ! n]v\s sy/em4 ,! n]v\s    
sy/em holds ! :ole body toge!r 9 "o     
h>moni\s :ole2 x is ! gov]n+            
organization ( ! multicellul> community 
7,section #ee71 & ! supreme head ( !    
gov]nm5t resides 9 ! bra91 & is call$ ! 
m9d4 ,b j z 9 a political /ate only !   
mo/ important & mo/ exceptional duties  
are p]=m$ by ! imp]ial body1 & m9or     
matt]s & que/ions ( r\t9e are ref]r$ to 
bo>ds & local au?orities1 s ! m9d takes 

cognisance only ( a few ( ! high]       
conc]ns ( ! animal1 & a l>ge am\nt ( !  
"w ( ! n]v\s sy/em goes on ins5sibly1 9 
a p]fectly automatic way-- ev5 mu* t    
occurs 9 ! bra94   ,section #aja4 ,!    
prim>y elem5ts 9 ! tissue ( ! n]v\s     
sy/em are ?ree2 n]ve fibres1 :i* are    
simply conduct+ ?reads1 telegraph wires2
 ganglion cells1 :i* are ! (ficials ( ! 
sy/em2 & neuroglia1 a f9e v>iety (      
connective tissue :i* holds ^! o!r      
elem5ts toge!r1 & may also possibly     
ex]cise a function 9 affect+            
impressions4 ,a message along a n]ve to 
a ganglion cell is an aff]5t impression1
 f a cell to a muscle or o!r ext]nal end
 is an eff]5t impression4 ,! passage (  
an impression may be def9$ z a fla% (   
kataboly along ! n]ve1 & s e feel+1     
?\ght1 & det]m9ation involves ! =mation 
( a c]ta9 quantity ( kata/ases1 & !     
necessity = air & nutrition4   ,section 
#ajb4 ,unlike telegraph wires1 to :i* !y
 are (t5 comp>$1 n]v\s fibres usually   
convey impressions only 9 "o direction1 

ei!r c5trally 7aff]5t or s5sory n]ve    
fibres71 or outw>dly 7eff]5t or motor   
n]ve fibres74 ,b ! s-call$ motor n]ve   
fibres include n only ^? t set muscles 9
 motion1 b ^? t excite secretion1 *eck  
impulsive movem5ts1 & gov]n nutrition4  
,section #ajc4 ,figure #g1 ,%eet #h1 %[s
 ! typical /ructure ( n]v\s tissues4 ,! 
n]ve fibres !re figur$ are b\nd toge!r  
by endoneurium into small ropes1 !      
n]ves1 encas$ 9 p]9eurium4 ,!re is      
always a grey axis cyl9d] 7a4c471 :i*   
may 79 m$ullat$ n]ves71 or may n 79     
non-m$ullat$ or grey n]ves7 h a m$ull>y 
%ea? 7s4,s47 int]rupt$ at int]vals by ! 
nodes ( ,ranvi] 7n4,r474 ,nuclei 7n47 at
 int]vals "u ! %ea? indicate ! cells f  
:i* n]ve fibres are d]iv$ by a process (
 elongation4 ,! n]ves ( inv]tebrata1 :]e
 !y possess n]ves1 are mo/ly grey1 & s  
are ^? ( ! sympa!tic sy/em ( v]tebrata1 
to be pres5tly describ$1 g4c41 g4c4 are 
ganglion cells2 !y may h _m hair-l      
processes1 usually runn+ into cont9uity 
) ! axis cyl9d]s ( n]ve fibres1 9 :i*   

case !y are call$ multi-pol> cells1 or  
!y may be uni- or bi-pol>4   ,section   
#ajd4 ,! simple/ example ( ! action ( ! 
n]v\s sy/em is reflex action4 ,=        
in/ance1 :5 ! foot ( a frog1 or ! h& ( a
 s\ndly sleep+ p]son1 is tickl$ v g5tly1
 ! limb is mov$ away f ! irritation1 )\t
 any m5tal action1 & entirely )\t w be+ 
ex]cis$4 ,& :5 we g f light into        
d>kness1 ! pupil ( ! eye enl>ges1 )\t   
any direct consci\sness ( ! *ange ( its 
%ape on our "p4 ,simil>ly1 ! pres5ce or 
food 9 ! ph>ynx initiates a s]ies (     
movem5ts-- swall[+1 ! dige/ive movem5ts1
 & s on-- :i* 9 heal? are entirely      
beyond our m5tal scope4   ,section #aje4
 ,a va/ am\nt ( our activities are      
reflex1 & 9 su* action an eff]5t /imulus
 foll[s an aff]5t promptly & q          
me*anically4 ,x is only :]e eff]5t      
/imuli d n imm$iately become entirely   
transmut$ into outw>dly mov+ impulses t 
m5tal action comes 9 & an animal feels4 
,!re appe>s to be a direct relation     
betwe5 s5sation & motion4 ,= in/ance1 ! 

%rieks & o!r in/9ctive viol5t motions   
produc$ by pa91 %unt (f a c]ta9 am\nt ( 
n]v\s impression t w\ld o!rwise regi/]  
itself z additional pa9ful s5sation4    
,simil>ly mo/ wom5 & *ildr5 und]/& !    
com=t ( a good cry1 & its b5efit 9 %ift+
 (f a disagreeable m5tal /ate4          
,section #ajf4 ,! m9d receives & /ores  
impressions1 & ^! accumulat$ exp]i5ces  
are ! basis ( memory1 comp>ison1        
imag9ation1 ?\ght1 & app>5tly spontane\s
 w4 ,volunt>y actions diff] f reflex by 
! int]position ( ?is previ\sly /or$     
factor4 ,= in/ance1 :5 a frog sees a    
small object 9 front ( him1 t may or may
 n be an edible insect1 ! direct visual 
impression does n directly det]m9e 8    
subsequ5t action4 ,x revives a numb] (  
previ\s exp]i5ces1 an image already /or$
 ( simil> insects & associat$ ) pa9ful  
or pleasurable gu/atory exp]i5ces4 ,) ^!
 arise an emotional effect ( desire or  
repulsion :i*1 passes into action (     
capture or ! rev]se4   ,section #ajg4   
,volunt>y actions may1 by con/ant       

repetition1 become quasi-reflex 9 "*4 ,!
 intellectual phase is abbreviat$ away4 
,habits are once volunt>y & delib]at$   
actions becom+ me*anical 9 ?is way1 &   
slipp+ out ( ! sph]e ( m9d4 ,= in/ance1 
_m ( ! detail$ movem5ts ( writ+ & walk+ 
are p]=m$ )\t any att5tion to ! details4
 ,an excessive conc5tration ( ! att5tion
 ^u "o ?+ leads to abs5t-m9d$ness1 & to 
its consequ5t absurdities (             
inappropriate1 because imp]fectly       
acquir$1 reflexes4   ,section #ajh4 ,?is
 fluctuat+ scope ( m9d %\ld be rememb]$1
 m especially :5 we are consid]+ !      
probable m5tal /ates ( ! l[] animals4   
,an habitual or reflex action may h all 
! outw>d appe>ance ( delib]ate adju/m5t4
 ,we _c tell 9 any p>ticul> case h[ f> !
 m5tal comes 91 or :e!r x comes 9 at    
all4 ,see+ t 9 our own case consci\sness
 does n ent] into our commone/ & mo/    
necess>y actions1 into brea?+ &         
dige/ion1 = in/ance1 & sc>cely at all 9 
! details ( su* acts z walk+ & talk+ we 
might inf] t nature 0 economical 9 its  

use1 & t 9 ! case ( su* an animal z !   
,rabbit1 :i* foll[s a v limit$ r\t9e1 & 
9 :i* sc>cely any v]satility 9 em]g5cies
 is evid5t1 x mu/ be relatively         
inconsid]able4 ,p]haps aft] all1 pa9 is 
n scatt]$ s ne$lessly & lavi%ly ?r\gh\t 
! _w z ! enemies ( ! vivisectioni/ w\ld 
h u believe4    #g4 ,! ,n]v\s ,sy/em    
,section #aji4 ,a little m att5tion mu/ 
n[ be giv5 to ! detail$ anatomy ( !     
p]iph]al & c5tral n]ve ends4 ,a n]ve1 z 
we h po9t$ out1 t]m9ates c5trally 9 "s  
ganglion cell1 ei!r 9 a ganglion or 9 ! 
sp9al cord or bra92 p]iph]ally !re is a 
mu* great] v>iety ( end+4 ,we may h     
tactile 7t\*7 ends ( v>i\s k9ds1 & !    
simil> olfactory & gu/atory end organs2 
or ! n]ve may conduct eff]5t            
impressions1 & t]m9ate 9 a gl& :i* x    
excites to secretion1 9 a muscle        
end-plate1 or 9 fact1 any:]e1 :]e       
kataboly c be set go+ & en]gy dis5gag$4 
,we may n[ briefly adv]t to ! receptive 
n]ve ends4   ,section #aaj4 ,_m s5sory  
n]ves1 d\btless1 t]m9ate 9 f9e ends     

among ! tissues4 ,!re are also special  
t\* corpuscles1 ovoid bodies1 ar\nd :i* 
a n]ve tw9es1 or )9 :i* x t]m9ates4     
,section #aaa4 ,! eye 7,figure #h7 has a
 t\gh1 d5se1 out] coat1 ! scl]otic      
7sc471 )9 :i* is a highly vascul> &     
int]nally pigm5t$ lay]1 ! *oroid1 ^u :i*
 ! p]cipi5t n]v\s lay]1 ! ret9a 7r47    
re/s4 ,! *ief *amb] ( ! eye is fill$ ) a
 transp>5t jelly1 ! vitre\s hum\r       
7v4h474 ,9 front ( ! eye1 ! :ite        
scl]otic passes into ! transp>5t cornea 
7c474 ,! epid]mis is cont9u$ ov] ! out] 
face ( ?is z a ?91 transp>5t epi!lium4  
,! *oroid coat is cont9u$ 9 front by a  
r+-%ap$ muscle1 ! iris 7ir47 ! col\r$   
portion ( ! eyes4 ,?is iris enl>ges or  
contracts its c5tral ap]ture 7! black   
pupil7 by reflex action1 z ! am\nt (    
light dim9i%es or increases4 ,imm$iately
 beh9d ?is curta9 is ! cry/all9e l5s    
7l471 ! curvature ( ! ant]ior face or   
:i* is controll$ by ! cili>y muscle     
7c4m474 ,9 front ( ! l5s is ! aque\s    
hum\r 7a4h474 ,! description ( ! action 

( ?is app>atus involves ! explanation ( 
sev]al ( ! elem5t>y pr9ciples ( optics1 
& w be f\nd by ! /ud5t 9 any text-book (
 t subject4 ,"h x w\ld h no v in/ructive
 be>+1 ei!r on g5]al physiological      
consid]ations or ^u anatomical fact4    
,section #aab4 ,! /ructure ( ! ret9a    
dem&s full] notice4 ,figure #i %[s an   
enl>g$1 diagram ( a small portion ( ?is1
 ! p]cipi5t "p ( ! eye4 ,! optic n]ve   
7o4n4 9 ,figure #h7 ent]s ! eye at a    
spot call$ ! bl9d spot 7,b4,s471 & !    
n]ve fibres spread !nce ov] ! inn]      
ret9al surface4 ,f ?is lay] ( n]ve      
fibres 7o4n4 9 ,figure #i7 ?reads run   
outw>d1 ?r\gh c]ta9 cle> & granul>      
lay]s1 to an out]mo/ /ratum ( little    
rods 7r47 & fusi=m bodies call$ cones   
7c471 ly+ side by side4 ,! :ole ( !     
ret9a consi/s ( q transp>5t matt]1 & x  
is ?is out]mo/ lay] ( rods & cones 7r4 &
 c47 t receives & records ! visual      
impression4 ,?is turn+ ( ! recipi5t ends
 away f ! light is h>dly :at "o w\ld at 
fir/ expect-- x seems su* a r\ndab\t    

arrangem5t-- b x obta9s 9 all v]tebrata1
 & x is a /rik+ po9t ( comp>ison ) !    
ord9>y inv]tebrate eye4   ,section #aac4
 ,we may pause to call ! /ud5t's        
att5tion to a little po9t 9 ! physiology
 ( n]ves1 v happily illu/rat$ "h4 ,!    
function ( a n]ve fibre is ! conduction 
( impressions pure & simple2 ! light    
radiates ?r\gh ! fibr\s lay] ( ! ret9a  
)\t produc+ ! slighte/ impression1 & at 
! bl9d spot1 :]e ! rods & cones are     
abs5t1 & ! n]ve fibres are ga!r$ toge!r1
 no visual impressions are record$4 ,if 
!re is any d\bt z to ! exi/5ce ( a bl9d 
spot 9 ! ret9al picture1 ! pro( is easy4
 ,let ! read] %ut 8 left eye1 & reg>d ^!
 two a/]isks1 fix+ 8 gaze int5tly ^u !  
left-h& "o ( !m4     99   99  ,at a     
di/ance ( ?ree or f\r in*es f ! pap]1   
bo? spots w be focuss$ on 8 ret9a1 !    
left "o 9 ! c5tre ( vision1 & ! "r "o at
 "s spot int]nal to ?is1 & he w see !m  
bo? di/9ctly4 ,n[1 if he )draws 8 head  
sl[ly1 ! "r spot w ( c\rse appe> to     
approa* ! left1 & at a di/ance ( t5 or  

twelve in*es x w1 9 its approa*1 pass   
ov] ! bl9d spot & vani%1 to reappe> z he
 cont9ues to move 8 head away f ! pap]4 
,! function ( n]ve fibres is simply     
conduction1 & ! nature ( ! impressions  
!y convey is entirely det]m9$ by !      
nature ( _! di/al & proximal t]m9ations4
   ,section #aad4 ,c]ta9 small muscles 9
 ! orbit 7eye-socket7 move ! eye1 & by  
_! action contribute to our p]ception ( 
! relative position ( objects4 ,!re is a
 lea% ( f\r muscles ris+ f a spot beh9d 
! exit ( ! optic n]ve f ! cranium to !  
upp]1 "u1 ant]ior1 & po/]ior sides ( !  
eyeball4 ,^! are ! sup]ior1 inf]ior1    
ant]ior1 & po/]ior recti4 ,runn+ f !    
front ( ! orbit obliquely to ! und]side 
( ! eyeball is ! inf]ior oblique muscle4
 ,correspond+ to x above is a sup]ior   
oblique4 ,a la*rymal gl& lies 9 !       
po/]o-inf]ior angle ( ! orbit1 & a      
,h&]ian gl& 9 ! correspond+ position 9  
front4 ,9 addition to ! upp] & l[]      
eyelids ( ! human subject1 ! rabbit has 
a ?ird1 ! nictitat+ lid1 9 ! ant]ior    

corn] ( ! eye4   ,section #aae4 ,! e>   
7,%eet ,,vii47 consi/s ( an ess5tial    
organ ( he>+1 & ( c]ta9 sup]add$ p>ts4  
,! ess5tial "p is call$ ! int]nal e>1 & 
is repres5t$ 9 all ! true v]tebrata     
7i4e41 exclud+ ! lancelet & its allies74
 ,9 ! l[] =ms x is a holl[ membran\s    
/ructure1 emb$d$ 9 a mass ( c>tilage1 ! 
otic capsule2 9 ! mammal ! latt] is     
entirely ossifi$1 to =m ! p]iotic bone4 
,! int]nal e> consi/s ( a c5tral sac1 f 
:i* ?ree semicircul> canals spr+4 ,!    
planes ( ! ?ree canals are mutually at  
"r angles2 two are v]tical1 ! ant]ior & 
po/]ior 7p4v4c47 v]tical canals1 & "o is
 horizontal1 ! horizontal canal 7h4c474 
,!re are dilatations1 call$ ampullae1 at
 ! ant]ior base ( ! ant]ior1 & at !     
po/]ior base ( ! po/]ior & horizontal   
canals4 ,indirectly connect$ ) ! ma9 sac
 is a spirally-twi/$ portion1 resembl+ a
 snail %ell 9 =m1 ! co*lea4 ,?is la/ "p 
is di/9ctive ( ! mammalia1 b ! re/ ( !  
int]nal e> is repres5t$ 9 all v]tebrata1
 ) "o or two exceptions4 ,! :ole ( !    

labyr9? is membran\s1 & conta9s a fluid1
 ! endolymph2 betwe5 ! membran\s wall ( 
! labyr9? & ! enclos+ bone is a space   
conta9+ ! p]ilymph4 ,/range z x may     
appe> at fir/1 ! entire l9+ ( ! int]nal 
e> is1 at an e>ly /age1 cont9u\s ) !    
g5]al epid]mis ( ! animal4 ,x gr[s 9 j z
 a gl& might gr[ 91 & is f9ally cut (f f
 ! ext]ior2 b a consid]able relic ( ?is 
=m] communication rema9s z a ?91 v]tical
 bl9d tube 7n %[n 9 ! figure71 ! ductus 
endolymphaticus4   ,section #aaf4 ,!    
eigh? n]ve runs f ! bra9 case 7,cr471   
into ! p]iotic bone1 & is di/ribut$ to !
 sev]al portions ( ?is labyr9?4 ,9 an   
ord9>y fi% ?is int]nal e> is ! sole     
auditory organ we %\ld f9d2 ! s\nd-waves
 w\ld travel ?r\gh ! wat] to ! ela/ic   
cranium & s rea* & affect ! n]ves4 ,b 9 
all air-frequ5t+ animals ?is orig9al    
plan ( an e> has to be add$ to1 to fit x
 to ! mu* fa9t] s\nd vibrations ( !     
compressible & f> less ela/ic air4 ,a   
receiv+ app>atus is ne$$1 & is suppli$  
by ! e>-drum1 middle e>1 or tympanic    

cavity 7,t474 ,9 ! mammal !re is also a 
collect+ e> trumpet 7! e> commonly      
s-call$71 ! ext]nal e>1 & ext]nal       
auditory meatus 7e4a4m474 ,a tightly    
/ret*$ membrane1 ! tympanic membrane1   
sep>ates ?is f ! drum4 ,a *a9 ( small   
bones1 ! malleus 7m471 ! incus 7i471 !  
os orbicul>e 7o4or471 a v small bone1 & 
a /irrup-%ap$ /apes1 sw+ across !       
tympanum1 f ! tympanic membrane to !    
int]nal e>4 ,at two po9ts ! bony        
inve/m5t ( ?is la/ is incomplete-- at ! 
f5e/ra rotunda 7f4r471 & at ! f5e/ra    
ovalis1 7f4o471 into :i* latt] ! end ( !
 /apes fits1 & s communicates ! s\nd    
vibrations ( ! tympanic membrane to !   
endolymph4 ,a passage1 ! ,eu/a*ian tube1
 communicates betwe5 ! tympanic cavity &
 ! ph>ynx 7,ph471 & s]ves to equalize ! 
pressure on ei!r side ( ! drum-head4 ,a 
comp>ative /udy ( ! e>s ( ! v]tebrata   
br+s to light ! fact t1 z we desc5d 9 ! 
animal scale1 ! f\r e> ossicles are     
replac$ by l>ge bones & c>tilages       
connect$ ) ! jaw1 & ! drum & ,eu/a*ian  

tube by a gill slit4 ,we h1 9 fact1 9 ! 
e>1 z ! /ud5t w p]ceive 9 ! sequel1 an  
ess5tially aquatic auditory organ1 add$ 
to & pat*$ up to fit ! new ne$s ( a life
 out ( wat]4   ,section #aag4 ,!        
impressions ( smell are conduct$ ?r\gh !
 fir/ n]ve to ! bra91 & are fir/ receiv$
 by special hair-be>+ cells 9 !         
olfactory muc\s membrane ( ! upp] "p ( !
 nasal passage4 ,! s5se ( ta/e has a    
special n]ve 9 ! n9?1 ! fibres ( :i*    
t]m9ate 9 special cells & cell          
aggregates 9 ! little papillae 7velvet  
pile-l processes7 t cov] ! tongue4      
,section #aah4 ,at an e>ly /age 9       
developm5t1 ! bra9 ( a mammal consi/s ( 
a l9e> arrangem5t ( ?ree holl[ vesicles 
7,figure #e1 ,%eet ,,viii41 #a1 #b1 &   
#c71 :i* are ! =e-1 mid-1 & h9d-bra9    
respectively4 ,! cavities 9 ^! 9 ^!     
vesicles are cont9u\s ) a holl[ runn+   
?r\gh ! sp9al cord4 ,on ! dorsal side ( 
! =e-bra9 is a /ructure to be dealt ) m 
fully lat]1 ! p9eal gl& 7p4g471 :ile on 
its "u surface is ! pituit>y body 7pt474

   ,section #aai4 ,! l[] figure ( 7#e7  
%[s1 9 a diagrammatic mann]1 ! d]ivation
 ( ! adult bra9 f ?is primitive /ate4 ,f
 ! =e-bra9 vesicle1 a holl[ outgr[? on  
ei!r side gives rises to ! 7pair$7      
c]ebral hemisph]e 7c4h471 :i* is        
prolong$ =w>d z ! olfactory lobe 7o4l474
 ,f ! =e-bra9 ! ret9a ( ! eye & ! optic 
n]ve also orig9ate z an1 at fir/1 holl[ 
outgr[? 7op474 ,! ro( ( ! mid-bra9 is   
also ?ick5$1 & bulges up to =m two pairs
 ( ?ick5+s1 ! corpora quadrigem9a1      
7c4q474 ,! h9d-bra9 s5ds up 9 front a   
m$ian outgr[?1 :i* develops lat]al w+s1 
! c]ebellum 7cbm471 beh9d :i* ! rema9d] 
( ! h9d-bra9 is call$ ! m$ulla          
oblongata1 & passes )\t any v def9ite   
dem>cation into ! sp9al cord4   ,section
 #abj4 ,figure #a is a correspond+      
figure ( ! actual /ate ( affairs 9 !    
adult4 ,! bra9 is se5 9 m$ian v]tical   
section4 7*47 is ! "r c]ebral hemisph]e1
 an inflat$ vesicle1 :i*1 9 ! mammal-- b
 n 9 our l[] types-- rea*es back ov] !  
re/ ( ! =e-bra91 & also ov] ! mid-bra91 

& hides ^! & ! p9eal gl& 9 ! dorsal view
 ( ! bra9 7,figure #b74 ,! holl[ ( !    
hemisph]e on ei!r side communicates ) ! 
?ird v5tricle1 ! orig9al cavity ( !     
=e-bra9 7#a 9 ,figure #e71 by an ap]ture
 7! =am5 ( ,monro71 indicat$ by a black 
arr[ 7f4,m474 ,besides _! orig9al       
communication ?r\gh ! int]m$iation ( !  
=e-bra91 ! hemisph]es are also unit$    
above its ro( by a broad bridge ( fibre1
 ! corpus callosum 7c4c471 :i* is       
di/9ctive ( ! mammalian animals4 ,!     
orig9al =e-bra9 vesicle has its lat]al  
walls ?ick5$ to =m ! optic ?alami       
7o4?471 betwe5 :i* a middle commissure1 
7m4c471 abs5t 9 l[] types1 /ret*es l a  
great beam across ! ?ird v5tricle4 ,!   
orig9al =e-bra9 is (t5 call$ !          
?alam5cephalon1 ! hemisph]e1 !          
pros5cephalon1 ! olfactory lobes1 !     
rh95cephalon4   ,section #aba4 ,! p>ts (
 mid-bra9 7mes5cephalon7 w be easily    
recognis$4 ,its cavity is 9 ! adult     
mammal call$ ! it]2 its floor is        
diff]5tiat$ into bundles ( fibres1 !    

crura c]ebri 7c4cb471 figur$ also 9     
,figure #d4   ,section #abb4 ,!         
c]ebellum 7met5cephalon7 consi/s ( a    
c5tral mass1 ! v]mis 7v4cbm471 & x also 
has lat]al lobes 7l4l471 prolong$ into  
flocculi 7f4cbm471 :i* la/>e -em-b$d$ 9 
pits1 9 ! p]iotic bone1 & on t acc\nt   
r5d] ! extraction ( ! bra9 f ! cranium  
f> m difficult ?an x w\ld o!rwise be4 ,!
 ro( ( ! h9d-bra91 be=e & beh9d !       
c]ebellum1 consi/s ( extremely ?9 plates
 ( n]v\s matt]4 ,its floor is greatly   
?ick5$ to =m ! mass ( ! m$ulla1 & 9     
front a great transv]se track ( fibres  
is specializ$1 ! pons ,v>olii 7p4,v474  
,its cavity is call$1 ! f\r? v5tricle4  
,section #abc4 ,figure #b gives a dorsal
 view ( ! rabbit's bra92 a horizontal   
slice has be5 tak5 at ! level ( ! corpus
 callosum4 ,! lat]al v5tricle 7i4e41 !  
holl[s ( ! hemisph]e7 is n yet op5$4 ,a 
l[] cut 7,figure #c7 exposes ?is        
7,v4,l474 ,! level ( ^! slices is       
approximately indicat$ 9 ,figure #a by !
 l9es ,a & ,b4 ,?is latt] figure w repay

 c>eful exam9ation4 ,! arr[1 ar41       
plunges into ! ?ird v5tricle1 beh9d !   
great middle commissure 7m4c471 & ! b>b 
is suppos$ to lie "u ! ro( ( ! mid-bra91
 ! corpora quadrigem9a 7c4q474 ,!       
position ( ar4 is also indicat$ 9       
,figure #a4 ,be=e read+ on1 ! beg9n]    
%\ld /op a :ile "h2 he %\ld c>efully    
copy or trace our figures &1 putt+ !    
book aside1 "n ! p>ts1 & he %\ld !n     
recopy1 on an enl>g$ scale1 & f9ally    
draw f memory1 correct1 & aga9 draw4 ,by
 do+ ?is be=e ! bra9 is dissect$ a      
consid]able sav+ ( "t is possible4      
,section #abd4 ,proce$+ f ! bra9 are    
twelve pairs ( cranial n]ves4 ,f !      
=e-bra9 spr+ two pairs1 :i* diff] f !   
re/ ( ! cranial n]ves 9 be+1 fir/ ( all1
 holl[ outgr[?s ( ! bra9-- ! o!rs are f 
! beg9n+ solid4 ,! fir/ n]ve is !       
olfactory lobe1 :i* s5ds num]\s filam5ts
 ?r\gh ! e?moid bone to ! olfactory     
organ4 ,! second is ! optic n]ve1 !     
visual s5sory n]ve4   ,section #abe4 ,! 
mid-bra9 gives rise to only "o n]ve1 !  

?ird1 :i* supplies all ! small muscles (
 ! eye 7see ,section #aad71 except !    
sup]ior oblique & ext]nal rectus4       
,section #abf4 ,! rema9d] ( ! n]ves spr+
 f ! h9d-bra94 ,! f\r? pair supply !    
sup]ior obliques1 & ! six? ! ext]nal    
recti2 s t ,,iii41 ,,iv41 & ,,vi4 are   
alike purely motor n]ves1 small &       
di/ribut$1 to ! orbit4 ,! fif? n]ve1 !  
trigem9al1 is a mu* l>g] & m important  
"o2 x is a mix$ n]ve1 hav+ ?ree ma9     
bran*es1 ( :i* ! fir/ two are *iefly    
s5sory1 ! ?ird almo/ entirely motor2 x  
lies deeply 9 ! orbit4 ,v#a 7see ,%eet  
#i7 runs up ov] ! recti beh9d ! eyeball1
 x is ! oph?almic bran*2 ,v#b1 !        
maxill>y bran*1 runs deeply "u ! eyeball
 & em]ges 9 front ( ! mal>1 & ,v#c1 !   
m&ibul> bran*1 runs d[n on ! inn] side (
 ! jaw-bone to ! jaw muscles & tongue4  
,section #abg4 ,if ! /ud5t w n[ recur to
 ! figures ( ! dog's skull 7,%eet #f71  
he w see c]ta9 ap]tures indicat$ 9 !    
cranial wall4 ,( ^!1 o4f4 is ! optic    
=am5 = ! exit ( n]ve ,,ii41 p]=at+ !    

orbito-sph5oid4 ,beh9d ?is !re comes an 
irregul> ap]ture1 7f4l4a471 ! =am5      
lac]um ant]ius1 giv+ exit to ,,iii41    
,,iv41 ,,vi41 & ,v#a4 ,v#b em]ges f !   
=am5 rotundum1 & ,v#c f ! =am5 ovale1   
two ap]tures unit+ beh9d a bony scre5499
 ,j 9 front ( ! bulla is a =am5 lac]um  
m$ium 7f4l4,m471 ?r\gh :i* no n]ve      
passes4  99 ,9 ! rabbit's skull f4l4    
ant]ius1 ! =am5 rotundum1 & =am5 ovale  
are n di/9ct1 & !re are two condyl>     
=am9a in/ead ( "o1 ?r\gh ea* ( :i*1 a   
moiety ( ,,xii4 passes4   ,section #abh4
 ,! eigh? n]ve 7auditory7 is purely     
s5sory1 ! n]ve ( ! special s5se ( he>+2 
x runs into ! p]iotic bone1 & breaks up 
on ! labyr9?4 ,! sev5? n]ve 7facial7 is 
almo/ entirely motor2 x passes ?r\gh !  
p]iotic ant]ior to ,,viii41 & em]ges by 
! /ylo-ma/oid =am5 7s4m4f47 beh9d !     
bulla1 to run outside ! great jaw muscle
 across ! *eek imm$iately "u ! sk9      
7,figure #a74   ,section #abi4 ,! n9?   
7glossoph>yngeal7 n]ve is *iefly s5sory2
 x is ! special n]ve ( ta/e1 & is       

di/ribut$ to ! tongue4 ,! t5? n]ve      
7vagus7 arises by a numb] ( roots1 &    
passes out ( ! skull1 toge!r ) ,,ix &   
,,xi1 by ! =am5 lac]um -po/]ium- po/]ius
 7f4l4p474 ,x is a conspicu\s :ite n]ve1
 & runs d[n ! neck by ! side ( ! common 
c>otid art]y4 ,x s5ds a sup]ior l>yngeal
 bran* 7,xa7 to ! l>ynx4 ,! left vagus  
passes v5tral to ! aortic ar*1 & s5ds a 
bran* 7l4x4b47 "u ?is along ! tra*ea to 
! l>ynx-- ! recurr5t l>yngeal n]ve4 ,!  
correspond+ n]ve on ! "r 7r4x4b47 loops 
"u ! subclavian art]y4 ,! ma9 vagus1    
aft] ?is bran*+1 passes beh9d ! he>t to 
! oesophagus & along x to ! /oma*4      
,,xi41 ! sp9al accessory1 supplies c]ta9
 ( ! neck n]ves4 ,,xii41 ! hypoglossal1 
runs out ( ! skull by ! condyl> =am5    
7c4f471 is motor1 crosses ! roots (     
,,xi41 ,x41 & ,,ix41 passes v5tral to ! 
c>otid1 & breaks up among ! muscles ( ! 
tongue & neck4   ,section #acj4 ,( !    
functions ( ! sev]al p>ts ( ! bra9 !re  
is /ill v consid]able d\bt4 ,) disease  
or willful de/ruction ( ! c]ebral tissue

 ! p]sonal initiative is affect$-- !    
animal becomes m di/9ctly a me*anism2 ! 
c]ebellum is probably conc]n$ 9 !       
coord9ation ( muscul> movem5ts2 & !     
m$ulla is a c5tre = ! high] & m         
complicat$ respiratory reflexes1 yawn+1 
c\gh+1 & s on4 ,! great majority (      
reflex actions c5tre1 h[ev]1 9 ! sp9al  
cord1 & d n affect ! bra94   ,section   
#aca4 ,a cross section ( ! sp9al cord is
 %[n 9 ,figure #f1 ,%eet #h4 ,x is a    
cyl9d]1 almo/ bisect$ by a dorsal 7d4f47
 & a v5tral 7v4f47 fissure4 ,?r\gh its  
c5tre runs a c5tral canal 7c4c471       
cont9u\s ) ! bra9 v5tricles1 & l9$ by   
ciliat$ epi!lium4 ,! sp9al cord consi/s 
( an out] portion1 ma9ly ( n]v\s fibres1
 ! :ite matt]1 & ( inn]1 ganglionat$1 & 
m highly vascul> grey matt]4 7,9 !      
c]ebrum ! grey matt] is ext]nal1 & !    
:ite int]nal47 ,! cord1 l ! bra91 is    
surr\nd$ by a vascul> fibr\s inve/m5t1 &
 protect$ f concussion by a s]\s fluid4 
,! n]ves :i* em]ge f ! v]tebral column  
betwe5 ! v]tebrae1 arise1 unlike !      

cranial n]ves1 by two roots4 ,! dorsal (
 ^!1 ! s5sory root 7d4n471 has a swell+ 
^u x1 ! dorsal ganglion1 &-- by         
exp]im5ts ^u liv+ animals-- has be5 %[n 
to conta9 only aff]5t fibres2 ! v5tral1 
! motor root1 is )\t a ganglion1 &      
entirely or ma9ly motor4 ,! two unite   
outside ! cord1 & !reaft] ! sp9al n]ves 
are bo? s5sory & motor4   ,section #acb4
 ,besides ! great mass ( bra9 & sp9al   
cord 7c]ebro-sp9al axis71 !re is1 on    
ei!r side ( ! dorsal wall ( ! body      
cavity1 a sympa!tic n]v\s *a94 ,! n]ve  
fibres ( ?is sy/em1 l ! n]ve fibres (   
inv]tebrates1 are non-m$ullat$4 ,x may  
be se5 z a greyi% ?read runn+ close by !
 common c>otid 9 ! neck 7sym41 ,figure  
#a72 x !n runs ov] ! heads ( ! ribs 9 ! 
?orax & close beside ! dorsal aorta 9 ! 
abdom9al region4 ,9 ! ant]ior region ( !
 neck x dilates to =m a sup]ior c]vical 
ganglion1 & opposite ! fir/ rib x =ms an
 inf]ior c]vical ganglion4 ,!nce1       
backw>ds1 !re is a ganglion on ea*      
sympa!tic *a9 opposite ea* sp9al n]ve1 &

 ! two ex*ange fibres ?r\gh a ?read1 !  
ramus communicans4 ,to ! sympa!tic *a9  
is delegat$ mu* ( ! r\t9e "w ( reflex   
control ( ! bloodvessels & o!r visc]a1  
:i* w\ld o!rwise fall ^u ! sp9al cord4  
,section #acc4 ,!re are eight c]vical   
7sp9al7 n]ves1 "o 9 front ( ! atlas1 &  
"o beh9d ea* ( ! c]vical v]tebrae4 ,!   
la/ f\r & ! fir/ ?oracic 7sp9al7        
contribute to a lea% ( n]ves runn+ out  
to ! =e limb1 ! bra*ial plexus 7plexus1 
lit]ally network1 b "h mean+ a plait$   
cord74 ,! f\r? c]vical also s5ds d[n a  
phr5ic n]ve 7p4n41 ,figure #a71 along by
 ! ext]nal jugul> ve9 & ! sup]ior caval 
ve9 to ! diaphragm4 ,! la/ ?ree lumb> & 
! sacral n]ves =m a sacral plexus1      
supply+ ! h9d limb4   ,section #acd4 ,f 
! sympa!tic 9 ! h9d] region ( ! ?orax a 
n]ve1 ! great splan*nic n]ve1 arises1 & 
runs1 back to a ganglionat$ n]v\s       
network1 j beh9d ! coeliac art]y1 into  
:i* ! vagus also ent]s2 ?is is ! coeliac
 ganglion1 & toge!r ) a simil> sup]ior  
mes5t]ic ganglion ar\nd ! correspond+   

art]y1 makes up a subsidi>y visc]al     
n]v\s network1 ! sol> plexus4 ,a simil> 
& small] n]v\s tangle1 be>+ an inf]ior  
mes5t]ic ganglion1 lies ne> ! inf]ior   
mes5t]ic art]y4   ,section #ace4        
,f9ally1 we may note ! p9eal gl& & !    
pituit>y body1 z rem>kable app5dages    
above & bel[ ! ?alam5cephalon4 ,_!      
function1 if !y h a function1 is        
altoge!r unkn[n4 ,probably1 !y are      
inh]it$ f ance/ors to :om !y 7 ( value4 
,su* /ructures are call$ r$uc$ or       
ve/igial /ructures1 & among o!r in/ances
 are ! clavicles ( ! rabbit1 ! hair on  
human limbs1 ! little pulpy nodule 9 !  
corn] ( ! human eye1 repres5t+ !        
rabbit's ?ird eyelid1 & ! caudal        
v]tebrae at ! end ( ! human sp9al       
column4 ,9 c]ta9 l[ly reptiles1 9 !     
lampreys1 & especially 9 a peculi> ,new 
,zeal& liz>d1 ! p9eal gl& has ! mo/     
conv9c+ resemblance to an eye1 bo? 9 its
 g5]al build & 9 ! microscopic /ructure 
( its elem5ts2 & x seems n[ m ?an       
probable t ?is little vascul> pimple 9  

our bra9s is a relic ( a ?ird & m$ian   
eye possess$ by ance/ral v]tebrata4 ,!  
pituit>y body is probably equival5t to a
 ciliat$ pit we %all describe 9 !       
lacelet 7,amphioxus74    #h4 ,r5al &    
,reproductive ,organs  ,section #acf4   
,we h n[ really complet$ our survey ( ! 
individual animal's me*anism4 ,b no     
animal t 0 m]ely complete 9 itself w\ld 
be long sanction$ by nature4 ,= an      
animal species to survive1 !re mu/      
evid5tly1 also1 be prop] provision = !  
production ( "y1 & ! pres]vation ( !    
species z well z ( ! individual4 ,h5ce 9
 an animal's physiology & psy*ology we  
meet ) a va/ am\nt ( unselfi% provision1
 & its /ructure & happ9ess are m        
ess5tially dep5d5t on ! good ( its k9d  
?an on its n>r[ p]sonal advantage4 ,!   
mammalia probably owe _! pres5t dom9ant 
position 9 ! animal k+dom to !          
exceptional sacrifices made by !m = _!  
"y4 ,in/ead ( lay+ eggs & ab&on+ !m be=e
 or soon aft] hat*+1 ! females reta9 !  
eggs )9 _! bodies until ! developm5t ( !

 "y is complete1 & !reaft] associate )  
!m = ! purposes ( n\ri%m5t1 protection1 
& education4 ,9 ! matt] ( ! tail1 =     
in/ance1 already not$1 ! individual     
rabbit incurs ! disadvantage (          
conspicu\sness = ! re>1 9 ord] to fur!r 
! safety ( ! "y4   ,section #acg4 ,!    
female organs ( reproduction are %[n 9  
,%eet #aj4 ,! ess5tial organ is ! ov>y  
7ov471 9 :i* ! ova 7eggs7 are =m$4      
,figure #c gives an enl>g$ & /ill m     
diagrammatic r5d]+ ( ! ov>y4 ,!re is a  
support+ gr\nd mass1 or /roma1 into :i* 
num]\s bloodvessels & n]ves ent] & break
 up4 ,! ova appe> fir/ z small cells 9 !
 ext]nal sub/ance ( ! ov>y 7z at #a71 & 
move inw>d 7#b & #c71 surr\nd$ by a     
numb] ( si/] cells1 :i* af=d !m         
n\ri%m5t4 ,at 7#d7 an ovum ) its        
surr\nd+ gr\p ( cells is m di/9ct & ne> 
! c5tre ( ! ov>y2 a fluid is appe>+ )9 !
 ovisac z ! developm5t proce$s4 7#e7 is 
a mu* m mature ovisac or ,graafian      
follicle4  ,section #ach4 ,! ovum 7ov471
 is n[ l>ge1 & its nucleus & nucleolus  

7! g]m9al vesicle & spot7 are v di/9ct4 
,! wall ( ! follicle consi/s1 9 !       
mammal1 ( sev]al lay]s ( cells1 !       
membrana granulosa 7or granulosa        
simply72 ! ovum lies on its out] side   
emb$d$ 9 a mass ( cells1 discus         
prolig]us1 sep>at$ f actual contact ) ! 
ovum by a zona pellucida4 ,! rip5+      
follicle moves to ! surface ( ! ov>y &  
bur/s1 ! ovum falls into ! body cavity4 
,9 ,figure #b1 a ripe ,graafian follicle
 7,g4,f471 projects ^u ! ov>y4          
,section #aci4 ,! lib]at$ ovum is caught
 up by ! funnel-%ap$ op5+ ( ! ,fallopian
 tube1 :i* passes )\t any v conspicu\s  
dem>cation into ! cornu ut]i 7c4ut47 (  
its side2 ! two ut]9e cornua meet+      
toge!r 9 ! middle l9e =m ! vag9a 7,v471 
:i* runs out into a ve/ibule 7vb47 op5+ 
betwe5 tumid lips to ! ext]ior4 ,! ur9>y
 bladd] 7ur4b47 also op5s into !        
ve/ibule1 & receives ! two uret]s f !   
kidney4   ,section #adj4 ,9 ! male we   
f9d1 9 ! position ( ! female ut]us1 a   
ut]us mascul9us 7u4m474 ,! ess5tial     

sexual organ is ! te/is 7,t471 a compact
 mass ( coil+ tubuli1 :i* op5s by a     
numb] ( ducts1 ! vasa eff]5tia1 into a  
loos] & s(t] epididymis 7ep471 :i* s5ds 
! sexual product onw>d ?r\gh a vas      
def]5s 7v4d471 to op5 at ! base ( !     
ut]us mascul9us4 ,! ur9>y bladd] &      
uret]s correspond ) ^? ( ! female1 & !  
common urog5ital duct 7 ve/ibule71 !    
ure?ra1 is prolong$ into an erectile    
p5is 7,p47 surr\nd$ by a fold ( sk91 !  
prepuce4 ,a pro/ate gl& 7pr471          
contributes to ! male sexual fluid4 ,!  
"* ( ! ess5tial male elem5t1 !          
sp]matozoon1 ! g5]al nature ( !         
reproductive process1 w be conv5i5tly   
def]r$ until ! *apt]s ^u developm5t are 
rea*$4    #i4 ,classificatory ,po9ts    
,section #ada4 ,! foll[+ facts (        
classificatory importance may n[ be     
consid]$1 b _! full =ce w be bett]      
appreciat$ aft] ! /udy ( o!r v]tebrate  
types4 ,!y are su* z come prom95tly =w>d
 9 ! comp>ison ( ! rabbit ) o!r         
organisms4   ,section #adb4 ,9 ! fir/   

place1 ! rabbit is a metazoon1 "o ( !   
metazoa1 i4e41 a multicellul> organism1 
z comp>$ ) ! amoeba1 :i* belongs to !   
protozoa or "o-cell animals 7,section   
#ee74 ,9 ! next place1 x is ext]nally   
bilat]ally symmetrical1 its p>ts        
balance1 & :]e1 9 its int]nal anatomy1 x
 dep>ts f ?is symmetry 7z 9 ! case ( !  
aorta1 ! /oma* & inte/9es1 & ! kidneys71
 ! dep>ture has an appe>ance ( be+ !    
results ( p>tial r$uctions & di/ortions 
( an orig9ally q symmetrical plan4 ,& ! 
facts ( developm5t /r5g!n ?is idea2 9 ! 
v e>lie/ /ages we h pair$ aortic ar*es1 
( :i*1 ! left only rema9s1 a /raight    
alim5t>y canal1 & less asymmetrical     
kidneys4 ,9 ! va/ majority ( animals !  
same bilat]al symmetry is to be se51 b 9
 ! />-fi% & sea-ur*9s1 & 9 ! jelly-fi%1 
corals1 sea anemones1 & hydra1 ! g5]al  
=m ( ! animal is1 in/ead1 arrang$ r\nd a
 c5tre1 l a /> & its rays1 & ! symmetry 
is call$ radial4   ,section #adc4 ,we   
also see 9 v>i\s organs ( ! rabbit1 &   
especially 9 ! case ( ! limbs & v]tebral

 column1 :at is call$ metam]ic          
segm5tation1 t is1 a repetition ( p>ts1 
"o beh9d ! o!r1 along ! axis ( ! body4  
,?us ! bodies & ar*es ( ! v]tebrae      
repeat ea* o!r1 & s d ! sp9al n]ves4 ,! 
r5al organ ( ! rabbit1 "s "t be=e bir?1 
displays a metam]ic arrangem5t ( its    
p>ts2 b ?is disappe>s1 z developm5t     
proce$s1 into ! compact kidney ( !      
adult4 ,b ! metam]ic segm5tation 9 !    
rabbit's organism is n ne>ly s m>k$ z t 
( an e>?worm1 = in/ance1 :i* is visibly 
a *a9 ( r+s4 ,if ! /ud5t wants a p]fect 
figure ( metam]ic segm5tation he %\ld   
?9k ( a tra9 ( precisely simil>         
c>riages1 or a /r+ ( beads4 ,"o bead1 "o
 c>riage1 "o v]tebra1 w\ld be a metam]e4
   ,section #add4 ,9 contra/ to metam]ic
 segm5tation is ! antim]ic repetition ( 
radial symmetry 7,section #adb71 9 :i*  
ea* ray ( ! /> is call$ an antim]e4 ,x  
is possible to h bilat]al symmetry )\t a
 metam]ic arrangem5t ( p>ts1 z 9 !      
mussel & ! cuttle-fi%2 b metam]ic       
segm5tation )\t complete or r$uc$       

bilat]al symmetry does n occur4         
,section #ade4 ,we are n[ 9 a position  
to appreciate ! fact t ! old & m        
popul>ly "k division ( animals into     
v]tebrata & inv]tebrata sc>cely         
repres5ts ! facts ( ! case1 t ! prim>y  
division %\ld be into protozoa &        
metazoa1 & t ! v]tebrata are "o ( sev]al
 gr\ps ( metazoa ) a fundam5tal bilat]al
 symmetry & imp]fect metam]ic           
segm5tation4  ,! rabbit is "o ( !       
v]tebrata1 &1 9 common ) all ! o!r      
animals collect$ "u ?is head1 x has--   
7a7 ,a skeletal axis 7! v]tebral column7
 betwe5 its c5tral    n]v\s sy/em & its 
body cavity4 ,9 ! adult rabbit ?is      
consi/s ( a *a9 ( v]tebrae1 b 9 ! embryo
 7i4e41 !    "y rabbit be=e bir?7 x is  
repres5t$ by a cont9u\s *ord1    !      
noto*ord1 & x rema9s z su* 9 "s ( ! l[e/
    v]tebrata ?r\gh\t life4 ,9 o!r      
words1 9 ^! l[]    v]tebrata1 ! v]tebral
 axis is n metam]ic4     7b7 ,a dorsal &
 -,tubul> n]v\s axis4 7,section #aca1 ! 
c5tral    canal7     7c7 ,x has1 ?\gh 9 

! embryo only1 c]ta9 slits betwe5 !     
?roat & ! ext]ior1 l ! gill slits ( a   
fi%4 ,su*    slits are-- ) "o or two    
rem>kable exceptions outside !          
sub-k+dom-- di/9ctly v]tebrate features1
 & rema91 ( c\rse1    9 fi%es ?r\gh\t   
life4  ,! pres5ce ( true c>tilage & bone
 m>k a v]tebrate1 b v]tebrata occur 9   
:i* -^! tissues- bone -are- is abs5t4   
,section #adf4 ,! rabbit %>es ! foll[+  
features ) all ! v]tebrata1 except !    
true fi%es1 :i* d n possess any ( !m--  
7a7 ,lungs 7b _m fi% h a swimm+ bladd]  
:i* answ]s    to ! lungs 9 its          
anatomical relations47     7b7 ,limbs   
:i* consi/ ( a proximal jo9t ( "o bone  
an    int]m$iate "p ( two1 & a di/al    
portion :i* has five    digits1 or is   
evid5tly a r$uc$ =m ( ! five-digit      
limb499     7c7 ,! abs5ce ( a m$ian f9  
support$ by f9 rays49999     99 ,! frog 
%[s indications ( a six? digit4    9999 
,! frog's tadpole has a m$ian f91 b no  
f9 rays4   ,section #adg4 ,! rabbit %>es
 ! foll[+ features ) all ! v]tebrata    

above ! fi%es & amphibia 7 frogs1 toads1
 newts1 & etc47--     7a7 ,abs5ce (     
gills 7n gill slits1 note7 at any /age 9
    developm5t4     7b7 ,an amnion1 &   
7c7 ,an allantois 9 developm5t4  ,!     
mean+ ( 7b7 & 7c7 we %all expla9 to !   
/ud5t 9 ! *apt]s on embryology4 ,we     
simply m5tion !m "h to r5d] our table   
complete4   ,section #adh4 ,! rabbit    
%>es ) all mammals1 & diff]s f all o!r  
v]tebrata 7i4e41 birds1 reptiles1       
amphibia1 & fi%es71 9 hav+--     7a7    
,hair4     7b7 ,a diaphragm4     7c7    
,only "o aortic ar*1 & t on ! left side 
( ! body4     7d7 ,its "y born alive4   
7,b two v reptile-l mammals (           
,au/ralia1 ! duck-bill$ platypus & !    
e*idna1 lay eggs1 &    c]ta9 fi% &      
reptiles be> liv+ "y47     7e7          
,epiphyses to its v]tebral -c5tre-      
c5tra499     7f7 ,! c]ebral hemisph]es  
cov]+ ! mid-bra94     7g7 ,corpora      
quadrigem9a in/ead ( bigem9a4     7h7 ,a
 corpus callosum4     7i7 ,a spirally   
coil$ co*lea to ! int]nal e>4     7,9   

respect to h & i also1 ! e*idna &       
platypus are sc>cely    mammal9an47     
99 ,b c]ta9 mammals h no su* epiphyses4 
,section #adi4 ,! rabbit1 toge!r ) !    
h>es & conies1 rats & mice1 voles1      
squirrels1 beav]s1 cavies1 gu9eapigs is 
includ$ 9 t ord] ( ! class ( mammals :i*
 is call$ ! rod5tia1 & is di/+ui%$ by ! 
"* ( ! incisor tee? f o!r ord]s ( !     
class4    #aj4 ,que/ions & ,ex]cises    
#a4 ,describe ! v5\s circulation ( !    
rabbit 7) diagrams74 ,comp>e a ve9 &    
art]y4 ,comp>e ! di/ribution ( ! great  
v5\s trunks ) t ( ! art]ial sy/em4  #b4 
,con/ruct a g5]al diagram ( !           
circulation ( ! rabbit1 to %[ especially
 ! relation ( ! portal sy/em1 !         
lymphatics & lacteals1 & ! r5al         
circulation to ! ma9 blood curr5t4  #c4 
,draw ! alim5t>y canal ( ! rabbit f     
memory4  #d4 ,:at is a villus8 ,describe
 its epi!lium1 & ! vessels )9 x4 ,write 
z explicit an acc\nt z y c ( ! absorb5t 
action ( a villus4  #e4 ,tabulate !     
alim5t>y secretions1 & _! action on !   

food4  #f4 ,:at is botryoidal tissue8   
,:]e does x occur8 ,:at is kn[n ( its   
functions8  #g4 ,copy ,diagram ,i4      
7enl>g$71 & ins]t ^u x ! visc]al n]ves z
 f> z y c4  #h4 ,:at are ! mo/          
*>act]i/ic po9ts 9 ! mammalian v]tebral 
column8  #i4 ,describe c>tilage & bone1 
& comp>e !m ) "o ano!r4  #aj4 ,give an  
acc\nt ( ! amoeba1 & comp>e x ) a       
typical tissue cell 9 a metazoon 7e4g41 
! rabbit74  #aa4 ,give a g5]al acc\nt ( 
connective tissue4 ,:at is t5don8  #ab4 
,trace1 briefly1 ! increas$ modification
 ( tissues 9 ! v]tebrata4  #ac4         
,describe1 ) diagrams1 ! /ructure (     
blood4 ,/ate ! function ( ea* factor y  
describe4  #ad4 ,comp>e ! pectoral ) !  
pelvic limb & girdle4 ,:at o!r /ructures
 ( ! adult rabbit display a simil>      
repetition ( simil> p>ts8  #ae4 ,draw f 
memory typical v]tebrae f ea* region ( !
 v]tebral column4  #af4 ,:at are        
bilat]al symmetry & metam]ic            
segm5tation8  #ag4 ,give a s*$ule (     
di/9ctive mammalian features4  #ah4     

,describe ! rabbit's bra9 7) diagrams74 
#ai4 ,give a li/ ( ! cranial n]ves ( !  
rabbit1 & note _! orig9 9 ! bra94  #bj4 
,give a li/ ( ! n]ve ap]tures ( ! dog's 
skull4  #ba4 ,:at are ! *ief anatomical 
diff]5ces betwe5 a typical cranial1 a   
sp9al1 & a sympa!tic n]ve8  #bb4        
,describe & figure ! di/ribution ( n]ves
 ,v41 ,,vii41 ,,ix41 & ,x4  #bc4        
,describe ! muscles1 gl&s1 & n]ves ( !  
orbit ( ! rabbit4  #bd4 ,describe1 )    
figures1 ! eye ( ! rabbit4  #be4 ,give a
 diagram ( ! rabbit's int]nal e>4  #bf4 
,draw & describe ! e> ossicles4 ,:at is 
_! function8  #bg4 ,draw & /ate !       
precise position ( ! hyoid bone1 !      
clavicle1 ! calcaneum1 & ! olecranon    
process4  #bh4 ,describe1 z accurately z
 possible1 ! position ( palat9e bones1  
pt]ygoids1 ! e?moid bone1 ! pre- &      
basi-sph5oids1 9 ! dog's skull4  #bi4   
,:at is membrane bone8 ,:at is c>tilage 
bone8 ,discuss _! mutual relation%ip4   
#cj4 ,:at is an excretion8 ,:at are !   
*ief excretory products ( an animal8 ,h[

 are !y remov$8  #ca4 ,describe ! m9ute 
anatomy ( ! liv]4 ,give a g5]al acc\nt (
 its functions4  #cb4 ,describe ! m9ute 
anatomy ( ! kidney1 & ! functions ( !   
sev]al p>ts4  #cc4 ,:at is ciliat$      
epi!lium8 ,:]e does x occur 9 ! rabbit8 
#cd4 ,describe ! me*anism ( respiration4
 ,:at is ! relation ( respiration to !  
g5]al life ( ! animal8  #ce4 ,:at are ! 
functions ( ! sk98 ,describe its        
/ructure4  #cf4 ,:at is a secretion8    
,tabulate & classify secret>y organs4   
,:at is a goblet cell8  #cg4 ,draw1 f   
memory1 ! dorsal & v5tral aspects (1 & a
 m$ian section ?r\gh1 a dog's skull4    
#ch4 ,"n any /ructures t appe> to y to  
be ve/iges or rudim5ts1 i4e41 /ructures 
)\t adequate physiological reason1 9 !  
rabbit's anatomy4  #ci4 ,h[ are su*     
/ructures int]pret$8  #dj4 ,describe !  
/ructure ( /riat$ muscul> fibre4        
,describe its functions1 & ! v>i\s means
 by :i* !y may be call$ into activity4  
#da4 ,describe ! *>act]s & /ructure ( ! 
blood ( ! rabbit4 ,:at is ! lymphatic   

sy/em8 ,describe its relation to ! blood
 sy/em 9 a mammal4  #db4 ,describe !    
/ructure ( 7a7 blood1 7b7 hyal9e        
c>tilage1 7c7 bone1 9 ! rabbit2 7d7 po9t
 out ! mo/ important resemblances &     
diff]5ces betwe5 ^! tissues2 7e7 /ate   
:at y "k ( ! developm5t ( ! same        
tissues4  #dc4 ,draw diagrams1 ) ! p>ts 
nam$1 ( ! male & female g5]ative organs 
( ! rabbit4  #dd4 ,9 ! rabbit provid$   
dissect on "o side & demon/rate by means
 ( flag-labels ! ma9 trunk ( ! vagus    
n]ve1 ! phr5ic n]ve1 & ! recurr5t       
l>yngeal n]ve4  #de4 ,dissect ! rabbit  
provid$ s z to expose ! abdom9al visc]a4
 ,m>k ) flag-labels ! duct ( ! pancreas1
 ! uret]s1 & ! oviducts or ! sp]m ducts 
7z ! case may be74     ,_m ( ! above    
que/ions 7 actually set at ,london      
,univ]sity ,exam9ations 9 ,biology4 ,9  
,bo? ,editions4    -,! ,frog  #a4 ,g5]al
 ,anatomy  ,section #a4 ,we w n[ /udy ! 
adult anatomy ( ! frog1 & ?r\gh\t we    
%all make con/ant comp>isons ) t ( !    
rabbit4 ,9 ! rabbit we h a di/9ctly     

l&-lov+1 burr[+ animal2 x eats purely   
vegetable food1 & dr9ks b little4 ,9 !  
frog we h a ma9ly insectivor\s type1    
liv+ mu* 9 ! wat]4 ,?is involves ! moi/]
 sk91 ! %ort] alim5t>y canal1 & !       
abbreviat$ neck 7,rabbit1 ,section #b7 (
 ! frog2 ! tail is abs5t-- 9 a fi% x    
w\ld d ! "w ! frog accompli%es ) 8 h9d  
legs-- & ! ap]tures :i* are po/]ior 9 ! 
rabbit1 run toge!r into "o dorsal op5+1 
! cloaca4 ,!re is1 ( c\rse 7,rabbit1    
,section #d71 no hair ! sk9 is smoo?1 & 
an ext]nal e> is also abs5t4 ,!         
rem>kable loos5ess ( ! frog's sk9 is due
 to great lymph spaces betwe5 x & ! body
 wall4   ,section #b4 ,if we n[ comp>e !
 g5]al anatomy ( ! frog 7vide ,%eet #aa7
 ) t ( ! rabbit1 we notice t ! diaphragm
 is abs5t 7,rabbit1 ,section #d71 & !   
body cavity1 or coelom1 is1 ) !         
exception ( ! small bag ( ! p]ic>dium   
r\nd ! he>t1 "o cont9u\s space4 ,! =k$  
tongue is atta*$ 9 front ( ! l[] jaw1 & 
c be flick$ out & back ) great rapidity 
9 ! capture ( ! small insects ^u :i* !  

frog lives4 ,! po/]ior n>es op5 into !  
front ( ! m\?-- !re is no long nasal    
*amb]1 & no palate1 & !re is no long    
tra*ea betwe5 ! epiglottis & ! lungs4 ,!
 oesophagus is less di/9ct1 & passes    
gradually1 s f> z ext]nal appe>ances g1 
into ! bag-l /oma*1 :i* is mu* less     
inflat$ & transv]se ?an t ( ! rabbit4 ,!
 duod5um is n a ,u-%ap$ loop1 b makes "o
 toge!r ) ! /oma*2 ! pancreas lies      
betwe5 x & ! /oma*1 & is m compact ?an !
 rabbit's4 ,!re is no sep>ate pancreatic
 duct1 b ! bile duct runs ?r\gh !       
pancreas1 & receives a s]ies ( ducts f t
 gl& z x does s4 ,! ileum is %ort]1 !re 
is no sacculus rotundus1 & ! l>ge       
inte/9e has no caecum1 none ( !         
*>act]i/ic sacculations ( ! rabbit's    
colon1 & does n loop back to ! /oma*    
be=e ! rectum section comm5ces4 ,! anus 
op5s n ^u ! ext]ior1 b into a cloacal   
*amb]4 ,! ur9>y & g5ital ducts op5      
sep>ately into ?is cloaca1 & dorsally & 
po/]iorly to ! anus4 ,! s-call$ ur9>y   
bladd] is v5tral to ! inte/9e1 9 a      

position answ]+ to t ( ! rabbit1 b x has
 no connection ) ! uret]s1 & x is       
two-horn$4   ,section #c4 ,! sple5 is a 
small1 r\nd body1 n s intimately b\nd to
 ! /oma* z 9 ! rabbit1 b 9 ess5tially ! 
same position4   ,section #d4 ,mu* t we 
knew ( ! physiology ( ! frog is arriv$  
at ma9ly by inf]5ces f our mammalian k4 
,its hi/ology is ess5tially simil>4     
,ciliat$ epi!lium is common] & occurs m 
abundantly ?an 9 ! rabbit1 9 ! ro( ( !  
m\? = in/ance1 & its r$ blood corpuscles
 are mu* l>g]1 oval1 & nucleat$4        
,section #e4 ,! lungs ( ! frog are      
bag-l2 %elves & spongy p>titions project
 into _! cavities1 b ?is /ructure is mu*
 simpl] ?an t ( ! rabbit's lung1 9 :i* !
 bran*+ bron*i1 ! imp]fect c>tilag9\s   
r+s support+ !m1 alveoli1 art]ies &     
ve9s1 =m toge!r a quasi-solid mass4     
,section #f4 ,! me*anism ( respiration  
is fundam5tally diff]5t f t ( ! mammal4 
,! me?od is z foll[s3-- ,! frog op5s its
 ant]ior n>es1 & depresses ! floor ( !  
m\?1 :i* !re=e fills ) air4 ,! ant]ior  

n>es are !n clos$1 & ! floor m\? rises &
 =ces ! air into ! lungs-- ! frog1      
!re=e1 swall[s its air r ?an inhales x4 
,! respiratory in/rum5t ( ! rabbit is a 
suction pump1 :ile t ( ! frog is a      
buccal =ce pump4   ,section #g4 ,! he>t 
is n quadrilocul> 7i4e41 ( f\r *amb]s71 
b trilocul> 7( ?ree71 & two /ructures1 n
 se5 9 ,lepus1 ! truncus art]iosus & !  
s9us v5osus1 into ! latt] ( :i* ! v5\s  
blood runs be=e ent]+ ! "r auricle1 are 
to be not$4 ,! s+le v5tricle is block$ )
 b>s ( tissue t r5d] its int]ior1 n an  
op5 cavity1 b a spongy mass4 ,figure #b1
 ,%eet #aa1 %[s ! he>t op5$2 l4au4 &    
r4au4 are ! left & "r auricles          
respectively2 ! truncus art]iosus is se5
 to be imp]fectly divid$ by a great     
longitud9o-spiral valve 7l4s4v472 p4c4  
is ! pulmo-cutane\s art]y -go+ to !     
lungs- supply+ sk9 & lungs2 d4ao41 !    
dorsal aorta furni%+ ! supply ( ! body &
 limbs2 & c4a4 ! c>otid art]y go+ to !  
head2 all ( :i* vessels 7comp>e ,figure 
#a7 are pair$4   ,section #h4 ,x might  

be inf]r$ f ?is t pure & impure blood   
mix 9 ! v5tricle1 & t a blood ( uni=m   
quality fl[s to lungs1 head1 &          
extremities2 b ?is is n s4 ,! spongy    
nature ( ! v5tricle suffici5tly ret>ds  
?is mix+4 ,x w be not$ t ! op5+ (       
pulmon>y art]ies lies ne>e/ to ! he>t1  
next come ! aortic & c>otid ar*es1 :i* h
 a common op5+ at ,a4 ,fur!rmore1 at    
c4g4l4 ! c>otid art]y1 repeat$ly divides
 to =m a close me%work ( art]ioles1 !   
c>otid gl&1 =m+ a sponge-l plug 9 ?is   
vessel4 is a spongy mass ( matt]1 !     
c>otid gl& ins]t$ ^u ! c>otid4 ,h5ce !  
pulmon>y art]ies yawn ne>e/ = ! blood1  
&1 be+ %ort1 wide vessels1 pres5t ! lea/
 resi/ance to ! fir/ ru% ( blood-- ma9ly
 v5\s blood = ! "r auricle4 ,z !y fill  
up1 ! back resi/ance 9 !m becomes equal1
 & !n great]1 ?an ! resi/ance at ,a1 & !
 ru% ( blood1 n[ ( a mix$ quality passes
 ?r\gh t ap]ture4 ,x selects ! dorsal   
aorta1 because ! c>otid ar*1 plugg$ by !
 c>otid gl&1 (f]s ! great] resi/ance4   
,pres5tly1 h[ev]1 ! back resi/ance ( !  

fill$ dorsal aorta rises above ?is1 & ! 
la/ fl[ ( blood1 f ! v5tricul> sy/ole-- 
almo/ purely oxyg5at$ blood = ! left    
auricle-- goes on t[>ds ! head4         
,section #i4 ,at ! c>otid gl& ! c>otid  
art]y splits into -an- a -ext]nal       
c>otid- l+ual 7e4c471 & a deep] int]nal 
c>otid4 ,! dorsal aorta passes r\nd on  
ea* side ( ! oesophagus1 z indicat$ by !
 dott$ l9es 9 ,figure #b1 ,%eet #aa1 &  
meets its fell[ dorsal to ! liv]4 ,ea*  
ar* gives (f subclavian art]ies to !    
limbs1 & ! left1 imm$iately be=e meet+ !
 "r1 gives (f ! coeliaco-mes5t]ic art]y 
to ! alim5t>y canal4 ,?is orig9 ( !     
coeliaco-mes5t]ic art]y a little to !   
left1 is ! only asymmetry 7want (       
balance7 9 ! art]ial sy/em ( ! frog1 z  
contra/$ ) ! v ext5sive asymmetry ( !   
great vessels ne> ! he>t ( ! rabbit4    
,po/]iorly ! dorsal aorta =ks into two  
common iliac art]ies 7"r & left7 supply+
 ! h9d limbs4   ,section #aj4 ,figure #c
 gives a side view ( ! frog1 to display 
! circulation4     ,l9es f ,second      

,edition only4    ,! v5\s return to !   
he>t1 z 9 ! rabbit1 is by pair$ v5ae    
cavae ant]iores & by a s+le v5a cava    
inf]ior4 ,! factors ( !    ant]ior cava 
on ei!r side are an ext]nal jugul>      
7ex4j47 an    innom9ate ve9 794v47 &    
subclavian 7scl4v474 ,! la/ receives n  
only ! bra*ial ve9 7b4v47 f ! =e limb1 b
 also a l>ge ve9    br++ blood = ! sk91 
! cutane\s 7p4v474 ,! innom9ate ve9     
has also two *ief factors1 ! int]nal    
jugul> 7l4i4j4v47 & !    subscapul>     
7s4s4v474 ,! blood returns f ea* h9d    
limb by a    sciatic 7l4sc47 or femoral 
7f4m47 ve91 & ei!r passes to a r5al     
portal    ve9 7l4r4p471 :i* breaks into 
capill>ies 9 ! kidney1 or by a pair$    
pelvic ve9 7l4p4v4 9 ,figures #a & #c7  
:i* meets its fell[ 9 !    middle l9e to
 =m ! ant]ior abdom9al ve9 7a4ab4v47 go+
 =w>d    & unit+ ) ! 7m$ian7 portal ve9 
7p4v47 to ent] ! liv]4  -,! vessels are 
nam$ 9 ! ref]5ces to ! figure1 :i* %\ld 
be c>efully copi$ & ma/]$4 ,"h we ne$   
only- ,comp>+ ) ! rabbit1 we w\ld       

especially call att5tion to ! fact t !  
v5a cava inf]ior ext5ds po/]iorly only  
to ! kidney1 & t !re is a r5al portal   
sy/em4 ,! blood f ! h9d limbs ei!r fl[s 
by ! ant]ior abdom9al ve9 to ! portal   
ve9 & liv]1 or x passes by ! r5al portal
 ve9 to ! kidney4 ,!re ! ve9 breaks up1 
& we f9d 9 ! frog's kidney1 j z we f9d 9
 ! frog's & rabbit's liv]1 a triple     
sy/em ( 7a7 nutritive art]ial1 7b7      
aff]5t99 v5\s & 7c7 eff]5t9999 v5\s     
vessels4  99 a1 ad  to2 9999 e1 ex  out 
(4   ,?is ,section miss+ f ,second      
,edition4 -,section #aa4 ,x is n v      
improbable t ! kidney ( ! frog %>es1 or 
p]=ms1 "s ( ! functions ( ! rabbit's    
liv]1 or p>allel duties1 9 addition to !
 simply excretory function4 ,s9ce       
specialization ( cells mu/ be ma9ly !   
relatively excessive exagg]ation ( "s "o
 ( ! g5]al prop]ties ( ! undiff]5tiat$  
cell1 x is n a difficult ?+ to imag9e a 
gradual transition1 z we move f "o      
organism to ano!r1 ( ! functions ( gl&s 
& o!r cellul> organs4 ,x is probable t !

 mammalian kidney is1 physiologically1 a
 mu* less important 7?\gh /ill q        
ess5tial7 organ ?an ! /ructures :i*     
correspond to x 9 position & developm5t 
9 ! l[] v]tebrate types4-   ,section    
#ab4 ,! lymphatic sy/em is ext5sively   
develop$ 9 ! frog1 b1 9 ! place ( a     
complete sy/em ( di/9ctly organiz$      
vessels1 !re are great lymph s9uses     
7comp>e ,section #a74 ,9 ,figure #e1    
,%eet #ab1 ! position ( two lymph he>ts 
7l4h41 l4h47 :i* pump lymph into !      
adjac5t ve9s1 is %[n4   ,section #ac4 ,!
 skull ( ! frog w repay a full treatm5t1
 & w be dealt ) by itself lat]4 ,!      
v]tebral column 7,%eet #ab7 consi/s (   
n9e v]tebrae1 ! c5tra ( :i* h faces1 n  
flat1 b holl[ 9 front 7pro-coel\s71 &   
evid5tly )\t epiphyses 7comp>e !        
,rabbit74 ,! ant]ior is sometimes call$ 
! atlas1 b x is evid5tly n ! homologue (
 ! atlas ( ! rabbit1 s9ce ! fir/ sp9al  
n]ve has a correspond+ di/ribution to ! 
twelf? cranial ( ! mammal1 & s9ce1      
!re=e1 x is probable t ! mammalian skull

  ! frog's skull  "o 7or m7 v]tebrae    
incorporat$ ) x4 ,po/]iorly ! v]tebral  
column t]m9ates 9 ! uro/yle1 a calcifi$ 
unsegm5t$ rod4 ,! v]tebrae h transv]se  
processes1 b no ribs4   ,section #ad4 ,!
 =e-limb 7,figure #f1 ,%eet #ab7 consi/s
 ( an upp] segm5t ( "o bone1 ! hum]us1 z
 9 ! rabbit2 a middle section1 ! radius 
& ulna1 fus$ "h into "o bone1 & n1 z 9 !
 mammalian type1 sep>able2 ( a c>pus1 & 
( five digits1 ( :i* ! f\r? is ! longe/4
 ,! %\ld] girdle is m important &       
complete ?an t ( ! high] type4 ,!re is a
 scapula 7sc47 ) an unossifi$ c>tilag9\s
 supra-scapula 7s4sc472 ! ant]ior bord] 
( ! scapula answ]s to ! acromion4 ,on ! 
v5tral side a c>tilag9\s rod1 embrac$ by
 ! clavicle 7cl47 7a membrane bone 9 ?is
 type71 runs to ! /]num1 & answ]s to !  
clavicle ( ! rabbit4 ,9 ! place ( !     
rabbit's coracoid process1 is a coracoid
 bone 7co471 :i* rea*es f ! gl5oid      
cavity to ! /]num2 x is hidd5 on ! "r   
side ( ,figure #f1 :i* is a dorsal view 
( ! %\ld] girdle4 ,!re is a pre-omo/]num

 7o4/47 & a po/-omo/]num1 sometimes t]m$
 a xiphi/]num 7x474   ,section #ae4     
,figure #g %[s ! pelvic girdle & limb ( 
! frog4 ,!re is a femur 7f472 tibia &   
fibula 7t4 & f47 are completely fus$2 ! 
proximal bones ( ! t>sus1 ! a/ragalus   
7z471 & calcaneum 7cal47 are elongat$1  
!re are five long digits1 & 9 ! calc>   
7c47 an indication ( a six?4 ,)         
consid]able modifications ( =m1 ! ?ree  
lead+ con/itu5ts ( ! rabbit's pelvic    
girdle occur 9 relatively id5tical      
positions4 ,! greatly elongat$ ilium    
7il47 articulates ) ! s+le 7comp>e      
,rabbit7 sacral v]tebra 7s4v4 9 ,figure 
#e74 ,! is*ium 7is47 is relatively      
small] ?an 9 ! rabbit1 & ! pubis 7pu47  
is a v5tral w$ge ( unossifi$ c>tilage4  
,! %ape ( ! pelvic girdle ( ! frog is a 
wide dep>ture f t f\nd among relat$ =ms4
 ,9 connection ) ! leap+ habit1 ! ilia  
are greatly elongat$1 & ! pubes & is*ia 
mu* r$uc$4 ,g5]ally ?r\gh\t !           
air-frequ5t+ v]tebrata1 we f9d ! same   
arrangem5t ( ^! ?ree bones1 usually 9 ! 

=m ( an inv]t$4 ,y-- ! ilium above1 !   
is*ium & pubis bel[1 & ! acetabulum at !
 junction ( ! ?ree4   ,section #af4 ,!  
uro-g5ital organs ( ! frog1 & especially
 ^? ( ! male1 correspond ) embryonic    
/ages ( ! rabbit4 ,9 ?is sex ! te/es    
7,t41 ,%eet #ac7 lie 9 ! body cavity1 & 
are :ite bodies usually dappl$ ) black  
pigm5t4 ,vasa eff]5tia 7v4e47 run to !  
int]nal bord] ( ! ant]ior "p ( ! kidney1
 :i* answ]s1 !re=e1 to ! rabbit's       
epididymis4 ,! h9d] "p ( ! kidney is !  
pr$om9ant r5al organ4 ,!re is a common  
uro-g5ital duct1 into :i* a sem9al      
vesicle1 :i* is especially l>ge 9 e>ly  
spr+1 op5s4 ,?is is ! p]man5t condition 
( ! frog4 ,9 ! rabbit1 = urog5ital duct1
 we h uret] & vas def]5s2 ! te/es & t   
ant]ior "p ( ! primitive kidney1 !      
epididymis1 %ift back into ! scrotal    
sacs1 & ! uret]s %ift r\nd ! rectum &   
e/abli% a direct connection ) ! bladd]1 
c>ry+ ! g5ital ducts loop$ ov] !m4 ,!   
oviducts ( ! female d n fuse di/ally to 
=m a m$ian vag9a z !y d 9 ! rabbit4 ,9  

front ( ! g5ital organ 9 bo? sexes is a 
corpus adiposum 7c4ad471 :i* acts z a   
fat /ore1 & is peculi> to ! frogs &     
toads4 ,! di/al end ( ! oviduct ( !     
female is 9 ! bre$+ season 7e>ly ,m>*7  
enorm\sly di/5d$ ) ova1 & ! ov>ies      
become !n ! m]e ve/iges ( _! =m] selves4
 ,! di/al end ( ! oviduct is1 !re=e1 n  
unfrequ5tly /yl$ ! ut]us4 ,!re is no    
p5is 9 ! male1 f]tilisation ( ! ova     
occurr+ z !y are squeez$ out ( ! female 
by ! embrac+ =e limbs ( ! male4 ,! male 
has a pad1 black 9 w9t]1 %[n 9 ,figure  
#a1 :i* is closely press$ aga9/ ! v5tral
 surface ( ! female 9 copulation1 & :i* 
s]ves z a ready means ( di/+ui%+ ! sex4 
,section #ag4 ,! sp9al cord has a g5]al 
simil>ity to t ( ! rabbit2 ! ratio ( its
 size to t ( ! bra9 is l>g]1 & ! n]ves  
numb] t5 pairs altoge!r4 ,! fir/ ( ^!   
7sp4 #a1 9 ,figure #b1 ,%eet -#ab- 7    
,fir/ ,edition error4 #ac corresponds 9 
di/ribution ) ! rabbit's hypoglossal    
n]ve1 a po9t we %all ref] to aga9 :5 we 
speak ( ! skull4 ,! second & ?ird       

con/itute ! bra*ial plexus4 ,! la/ ?ree 
=m ! sciatic plexus go+ to ! h9d limb4  
,section #ah4 ,! same ess5tial p>ts are 
to be f\nd 9 ! bra9 ( bo? frog & rabbit1
 b 9 ! =m] ! adult is n s widely modifi$
 f ! primitive condition z 9 ! latt]4 ,!
 =e-bra9 consi/s ( a ?alam5cephalon     
7?4c4 & #a71 :i* is expos$ 9 ! dorsal   
view ( ! bra91 & :i* has no middle      
commissure4 ,! c]ebral hemisph]es 7c4h47
 are n convolut$1 d n ext5d back to cov]
 p>ts beh9d !m1 z !y d 9 ! rabbit1 & are
 n connect$ above ! ro( ( !             
?alam5cephalon by a corpus callosum4    
,moreov]1 ! p>ts usually reg>d$1 z !    
olfactory lobes 7rh47 fuse 9 ! middle   
l9e4 ,! mid-bra9 gives rise to ! ?ird   
n]ve1 & has ! optic lobes on its dorsal 
side1 b ^! are holl[1 & !y are n        
subdivid$ by a transv]se groove into    
corpora quadrigem9a1 z 9 ! rabbit4 ,9 ! 
h9d-bra9 ! c]ebellum is a m]e b& (      
tissue )\t lat]al lobes or flocculi1 & !
 m$ulla gives orig9 only to n]ves f\r to
 t52 !re is no elev5? n]ve1 & !         

hypoglossal is ! fir/ sp9al-- f :i* x   
has be5 assum$ t ! rabbit's m$ulla      
equals t ( ! frog1 plus a portion ( !   
sp9al cord incorporat$ ) x4 ,!          
hypoglossal is v di/9ctly se5 on op5+ ! 
sk9 b5ea? ! hyoid plate4   ,section #ai4
 ,! fir/1 second1 ?ird1 & f\r? cranial  
n]ves ( ! frog correspond ) ^? ( !      
rabbit 9 orig9 & di/ribution4 ,s d five1
 six & eight4 ,! sev5? n]ve =ks ov] !   
e>-drum-- ! l>g] bran* em]g+ beh9d x &  
runn+ sup]ficially1 z %[n 9 ,figure #d4 
,!re is also a deep] palat9e bran* (    
,,vii4 7,p47 runn+ "u ,v#b & ,v#c bel[ !
 orbit1 & to be se5 toge!r ) ,v#a & ,v#b
 aft] removal ( ! eyeball4 ,! n9? n]ve  
simil>ly =ks ov] ! fir/ bran*ial slit ( 
! tadpole1 & evid5ce ( ! =k rema9s 9 !  
frog4 ,x is se5 curv+ r\nd ant]ior to ! 
hypoglossal n]ve1 & ly+ r deep] 9       
dissection4 ,! vagus 7t5?7 n]ve is      
di/ribut$ to he>t1 lungs1 & visc]a-- 9 !
 tadpole x also s5ds = =k+ bran*es ov] !
 second1 ?ird1 & f\r? bran*ial slits4 ,x
 lies deep] ?an ,,ix41 & int]nal to !   

ve9s1 & runs close beside ! cutane\s    
art]y4 ,mo/ ( ^! n]ves are easily       
dissect$ & no /ud5t %\ld re/ satisfi$   
until he has actually se5 !m4   ,section
 #bj4 ,! sympa!tic *a9 is closely       
connect$ ) ! aorta4 ,x is1 ( c\rse1     
pair$1 & is easily f\nd 9 dissection by 
lift+ ! dorsal aorta & look+ at its     
mes5t]y4 ,9 ! pres5ce ( ganglia         
correspond+ to ! sp9al n]ves1 & ( rami  
communicantes1 x resembles t ( ! rabbit4
   ,section #ba4 ,! :ole ( ?is *apt] is 
simply a concise comp>ison1 ( frog &    
rabbit4 ,9 addition to read+ x1 ! /ud5t 
%\ld v c>efully foll[ ! annotations to !
 figures1 & %\ld copy & recopy ^! side  
by side ) ! correspond+ diagrams ( ! o!r
 types4    #b4 ,! ,skull ( ! ,frog 7& ! 
v]tebrate skull g5]ally7  ,section #bb4 
,we h already giv5 a description ( !    
mammalian skull1 & we h /at$ :]e ! orig9
 ( ! sev]al bones 0 9 membrane1 & :]e 9 
c>tilage2 b a m complete compreh5sion ( 
! mammalian skull becomes possible ) !  
h&l+ ( a l[] type4 ,we propose n[1 fir/ 

to give "s %ort acc\nt ( ! developm5t & 
/ructure ( ! skull ( ! frog1 & !n to %[ 
briefly h[ its developm5t & adult       
arrangem5t demon/rate ! mammalian skull 
to be a fundam5tally simil> /ructure1   
complicat$ & disguis$ by fur!r          
developm5t & re-adju/m5t4   ,section    
#bc4 ,figure #a1;,i4 ,%eet #ad1 %[s a   
dorsal view ( a "y tadpole cranium2 !   
bra9 has be5 remov$1 & x is se5 t x 0   
support$ simply ^u two c>tilag9\s rods1 
! trabeculae cranii 7tr4c474 ,beh9d ^!  
trabeculae comes ! noto*ord 7n4c471 &   
ar\nd its ant]ior extremity is a pair$  
tract ( c>tilage1 ! p>a*ordals 7p4c474  
,^! /ructures1 und]ly+ ! skull1 are all 
t appe>s at fir/ ( ! bra9 box4 ,9 front1
 & sep>ate f ! cranium1 are ! nasal     
organs 7n4c472 ! eyes lie lat]ally to ! 
trabeculae1 & lat]ally to ! p>a*ordals  
are two tracts ( c>tilage enclos+ !     
int]nal e>1 ! otic capsules4   ,section 
#bd4 ,figure #a1 ,,ii41 is a m advanc$1 
phase ( ! same /ructures4 ,! trabeculae 
h met 9 front & s5t =w>d a m$ian 7c4t47 

& lat]al p>ts 7a4o47 to support ! nasal 
organs4 ,!y h also flatt5$1 out v       
consid]ably1 & h s5t up walls on ei!r   
side ( ! bra9 to meet above x & =m an   
incomplete ro( 7t47 ov] x4 ,! p>a*ordals
 h simil>ly gr[n up r\nd1 ! h9d-bra9 &  
=m$ a complete r+1 ! ro( ( :i* is       
indicat$1 by b4 ,fur!r1 ! otic capsules 
are fus+ ) ! bra9-case4 ,) c]ta9        
diff]5ces ( =m ^! elem5ts-- !           
trabeculae1 ! p>a*ordals1 & ! otic      
capsules1 are also ! fir/ =m$ /ructures 
( ! mammalian cranium4   ,section #be4  
,9 ,figures #a1;,i4 & ,,ii41 !re appe>s 
b5ea? ! eye a b> ( c>tilage 7p4p471 !   
palato-pt]ygoid c>tilage1 :i* is also to
 be se5 f ! side 9 ,figures #h1;,i4 &   
,,iii4 ,x w be le>nt f ^! latt] t ?is b>
 is jo9$ 9 front to ! cranium beh9d !   
nasal organ1 & beh9d to ! otic capsule4 
,! c>tilag9\s b> f ! palato-pt]ygoid to 
! otic capsule is call$ ! quadrate1 & at
 ! po9t ( junction1 at ! po/]o-v5tral   
angle ( ! palato-pt]ygoid1 articulates )
 ! c>tilag9\s b> :i* is de/9$ to =m !   

sub/ratum ( ! l[] jaw-- ,meckel's       
c>tilage 7,m4c4 9 ,figure #h1;,i474     
,section #bf4 ,figure #b %[s a dorsal   
view ( ^! /ructures 9 a "y frog4 ,! p>ts
 correspond+ to ^! 9 #a1;,,ii4 w be     
easily made out1 b n[ ossification has  
set 9 at v>i\s po9ts ( ?is c>tilag9\s   
cranium4 ,9 front ( ! otic capsule is ! 
pair$ pro-otic bone 7p4o472 beh9d x at !
 sides ( ! p>a*ordal r+ is ! pair$      
ex-occipital 7e4o472 9 front ( ! cranium
 box1 & beh9d ! nasal capsules1 is a r+ 
( bone1 ! 7m$ian1 b orig9ally pair$7    
sph5e?moid 7s4e474 -,a pair$            
ossification appe>s 9 ! palato-pt]ygoid 
c>tilage ! pt]ygoid bone 7pt471 :ile- ,a
 spl9t ( bone1 ! quadrato-jugal1 appe>s 
at ! angle ( articulation ) ! l[] jaw4  
,^! are all ! c>tilage bones t appe> 9 !
 cranium & upp] jaw ( ! frog4   ,section
 #bg4 ,b ano!r s]ies ( bones1 develop$  
fir/ *iefly 9 d]mal connective tissue1 &
 com+ to plate ov] ! cranium ( c>tilage1
 are n %[n 9 ,figure #b4 ,!y are1 h[ev]1
 9 ,figure #c4 ,^! membrane bones are3  

along ! dorsal middle l9e1 !            
p>ieto-frontals 7p4f471 orig9ally two   
pairs ( bones :i* fuse 9 developm5t1 & !
 nasals 7na474 ,r\nd ! edge ( ! jaw1 &  
be>+ ! tee?1 are pre-maxillae 7p4m471 & 
maxillae 7mx471 & ov]ly+ ! quadrate     
c>tilage & lat]al to ! otic capsules are
 ! ,t-%ap$ squamosal bones 7sq474 ,9 !  
v5tral view ( ! skull 7,figure #d7 we   
see a pair ( vom]s 7vo47 be>+ tee?1 a   
pair ( palat9es 7pal471 & a pair (      
pt]ygoids 7pt47 7:i* palat9es &         
pt]ygoids1 we may note1 unlike ^? ( !   
rabbit1 are -/at$ to be- membrane       
bones71 & a great m$ian dagg]-%ap$      
p>a-sph5oid 7p4sp474 ,^! two ,figures1 &
 #e1 :i* %[s ! same bones 9 side view1  
%\ld be c>efully ma/]$ be=e ! /ud5t     
proce$s ) ?is *apt]4 ,! c>tilage bones  
are di/+ui%$ f membrane bones by        
cross-%ad+4   ,section #bh4 ,turn+ n[ to
 ,figure #h1;,i41 we h a side view ( a  
tadpole's skull4 ,on ! v5tral side ( !  
head is a s]ies ( v]tical c>tilag9\s    
b>s1 ! visc]al ar*es support+ ! walls ( 

! tadpole's gill slits4 ,! fir/ ( ^! is 
call$ ! hyoid ar* 7c4h471 & ! f\r foll[+
 ?is1 ! fir/ 7br4#a71 second1 ?ird1 &   
f\r? 7br4#d71 bran*ial ar*es4 ,altoge!r 
!re are f\r gill slits & betwe5 ! hyoid 
ar* & ! jaw ar*1 z x is call$ 7         
,meckel's c>tilage  ! palato-pt]ygoid71 
is an imp]=ate slit1 :i* becomes !      
e>-drum499 ,! frog no long] brea!s by   
gills1 b by lungs1 & ! gills are lo/1 ! 
gill slits clos$1 & ! bran*ial ar*es    
consequ5tly mu* r$uc$4 ,figures #h1     
,,ii41 & #h1 ,,iii41 %[ /ages 9 ?is     
r$uction4 ,! hyoid ar* becomes atta*$1  
to ! otic capsule1 & its m$ian v5tral   
plate1 includ+ also ! ve/iges ( ! fir/1 
second1 & f\r? bran*ial ar*es1 is call$ 
! hyoid app>atus4 ,9 ,figure #e1 !      
app>atus is se5 f ! side2 c4h4 is call$ 
! 7"r7 ant]ior cornu9999 ( ! hyoid4 ,!  
function ( ! hyoid app>atus 9 ! frog is 
to furni%1 a basis ( atta*m5t to !      
tongue muscles2 x rema9s c>tilag9\s1 ) !
 exception ( ! relic ( "o bran*ial ar*1 
:i* ossifies z ! ?yro-hyal 7,figure #g  

?4h474 ,x w be not$ t1 z developm5t     
proce$s1 ! angle ( ! jaw sw+s backw>d1 &
 ! hyoid app>atus1 %ifts relatively     
=w>d4 ,^! *anges ( position are indicat$
 9 ,figure #h1 ,,iii41 by little        
arr[-heads4  99 ,we may note "h t1      
comp>+ ! e> ( ! frog ) t ( ! rabbit1 !re
 is no ext]nal e>4 ,!re is1 moreov]1 no 
bulla support+ ! middle e>1 & ! tympanic
 membrane /ret*es betwe5 ! squamosal 9  
front & ! ant]ior cornu ( ! hyoid beh9d4
 ,a rod-l columella auris replaces ! *a9
 ( e> ossicles1 & may1 or may n1 answ]  
to ! /apes alone1 or ev5 possibly to !  
entire s]ies4 ,9 ! int]nal e> !re is no 
co*lea1 & ! otic mass is l>gely         
c>tilag9\s in/ead ( entirely bony4  9999
 ,plural cornua4   ,section #bi4 ,be=e  
proce$+ to ! comp>ison ( ! mammalian    
skull ) ?is1 we w\ld /rongly recomm5d ! 
/ud5t ?or\ghly to ma/] ?is portion ( !  
"w1 & 9 no way c he d ?is m ?or\ghly &  
quickly ?an by tak+ a p>boil$ frog1     
pick+ (f ! sk91 muscle1 & connective    
tissue f its skull1 & mak+ out ! v>i\s  

bones ) ! help ( our diagrams4          
,section #cj4 ,figure #i repres5ts1 9 ! 
mo/ diagrammatic way1 ! ma9 *anges 9 =m 
( ! ess5tial con/itu5ts ( !             
cranio-facial app>atus1 z we pass f !   
amphibian to ! mammalian skull4 ,f4 is !
 frog f ! side & beh9d2 b4c4 is !       
bra9-case1 o4c4 ! otic capsule1 e4 !    
eye1 n4c4 ! nasal capsule1 p4p4 !       
palato-pt]ygoid c>tilage1 mx4 ! maxill>y
 membrane bones1 sq4 ! squamosal1 & mb4 
! m&ible4 ,! /ud5t %\ld comp>e ) ,figure
 #e1 & conv9ce himself t he appreciates 
! diagrammatic r5d]+ ( ^! p>ts4 ,n[ all 
! di/9ctive diff]5ces 9 =m1 f ?is ( !   
dog's skull 7,d471 are r$ucible to two  
prim>y causes--     7#a7 ,! bra9 is     
enorm\sly l>g]1 & ! bra9-case is va/ly  
inflat$1 s t--        7a7 ! otic capsule
 becomes emb$d$ 9 ! bra9-case wall2     
7b7 ! palato-pt]ygoid rod lies          
completely und]nea? !       bra9-case   
in/ead ( lat]ally to x2        7c7 !    
squamosal tilts d[n & 91 in/ead ( d[n & 
out1       & ! l[] jaw articulates ) its

 out] surface in/ead       ( bel[ its   
inn]1 &1 moreov]1 ) ! enorm\s di/5tion  
( ! bra9-case x comes ab\t t ! squamosal
 is       incorporat$ ) its wall4       
7#b7 ,! maxilla ant]iorly & ! palat9e   
po/]iorly s5d d[n    palat9e plates t   
gr[ 9 to =m ! bony palate1 cutt+ (f    a
 nasal passage 7n4p47 f ! m\? cavity    
7m4p471 & c>ry+ !    po/]ior n>es f !   
front "p ( ! m\?1 z !y are 9 !    frog1 
to ! ph>ynx4 ,h5ce ! vom]s ( ! dog lie1 
n 9 !    ceil+ ( ! m\?1 b 9 ! floor (   
?is nasal passage4   ,section #ca4 ,!   
quadrate c>tilage ( ! frog is sup]s$$ by
 ! squamosal z ! susp5sorium ( ! l[]    
jaw4 ,x is greatly r$uc$1 !re=e2 b x is 
n entirely abs5t4 ,9 ! "y mammal1 a     
quadrate c>tilage c be trac$1 connect$ )
 ! palato-pt]ygoid c>tilage1 &          
articulat+ ) ,meckel's c>tilage4 ,its   
position is1 ( c\rse1 b5ea? ! squamosal1
 & j outside ! otic capsule4 ,z         
developm5t proce$s1 ! increase 9 size ( 
! quadrate1 does n keep pace ) t ( !    
skull /ructures4 ,x loses its connection

 ) ! palato-pt]ygoid1 & app>5tly        
ossifies z a small ossicle-- ! incus ( !
 middle e>4 ,a small nodule ( c>tilage1 
cut (f f ! proximal end ( ,meckel's     
c>tilage1 becomes ! malleus4 ,! /apes   
w\ld appe> to be d]iv$ f ! hyoid ar*4   
,h5ce ^! small bones seem to be ! relics
 ( ! disc>d$ jaw susp5sorium ( ! frog   
utiliz$ 9 a new function4 ,consid]able  
d\bt1 h[ev]1 atta*es to ?is             
int]pretation-- d\bt t1 if any?+1 is    
ga9+ gr\nd4   ,section #cb4 ,! tympanic 
bulla ( ! dog is n indicat$ 9 ,diagram  
#i1 & x w\ld appe> to be a new /ructure 
7neomorph71 n repres5t$ 9 ! frog4       
,section #cc4 ,besides ^! great         
diff]5ces 9 =m1 !re are important       
diff]5ces 9 ! am\nt & di/ribution (     
c5tres ( ossification ( ! skull ( frog &
 mammal4 ,!re is no p>asph5oid 9 !      
mammal992 &1 in/ead1 a complete s]ies ( 
ossifications1 ! m$ian-1 basi-1 &       
pre-sph5oids1 & ! lat]al ali- &         
orbito-sph5oids occur4 ,! po9ts c be    
r5d]$ mu* m lum9\sly 9 a diagram ?an 9 !

 text1 & we w\ld c\nsel ! /ud5t to      
comp>e ?is v c>efully ) t ( ! ,rabbit4  
99 ,fa9t ve/igeal indications occur 9 ! 
develop+ skulls ( "s insectivora4       
,section #cd4     -,cranium             
-,nasal 7pair$71 -,vom] 7pair$7         
-,fronto-,p>ietal1 ,sph5e?moid ,bone    
7m$ian71 ,eye1 ,pro-otic ,bone1         
,otic ,c>tilage1 ,ex-occipital 7pair$7  
-,p>a-sph5oid ,bone     -,upp] ,jaw     
-,pre-,maxilla 7pair$71 -,palat9e       
7pair$71 ,pt]ygoid 7pair$71             
-,squamosal1 ,quadrate ,c>tilage ,to #a4
       -,maxilla       #a4              
,quadrato-,jugal     -,l[] ,jaw         
,m5to-meckelian1 -,d5t>y1 -,articul>e-  
-,angulo ,spl5ial   ,section #ce4       
-,po9ts especially- ,additional po9ts to
 be notic$ are3     7#a7 ,! otic capsule
 7 p]iotic bone7 ( ! dog ossifies f a   
numb] ( c5tres1 "o ( :i* is equival5t to
 ! frog's prootic4     7#b7 ,! sev]al   
con/itu5ts ( ! l[] jaw are n to be      
di/+ui%$ 9 ! adult mammal4     7#c7 ,!  
frog has no la*rymal bone4   ,section   

#cf4 ,we are n[ 9 a position to notice1 
)\t any dang] ( misconception1 :at is   
call$ ! segm5tal !ory ( ! skull4 ,old]  
anatomi/s1 work+ f adult /ructure only1 
conceiv$ ! idea t ! bra9-case ( ! mammal
 repres5t$ ?ree inflat$ v]tebrae4 ,! mo/
 ant]ior _h ! pre-sph5oid = its body1 ! 
orbito-sph5oids = its neural processes1 
& ! ar* 0 complet$ above by ! frontals  
7frontal segm5t74 ,simil>ly1 !          
basi-sph5oids1 ali-sph5oids1 & p>ietals 
=m$ a second ar* 7p>ietal segm5t71 & !  
ex-1 basi-1 & supra-occipitals a ?ird   
7occipital segm5t74 ,if ?is 7 correct1 9
 ! frog1 :i* is a m primitive r5d]+ ( ! 
v]tebrate plan1 we %\ld f9d ! v]tebral  
*>act]s m di/9ct4 ,b1 z a matt] ( fact1 
z ! /ud5t w p]ceive1 frontal segm5t1    
p>ietal segm5t1 & occipital segm5t1 c no
 long] be trac$2 & ! mode ( orig9 f     
trabeculae & p>a-*ordals %[ v cle>ly !  
falsity ( ?is view4 ,! v]tebrate cranium
 is entirely diff]5t 9 nature f         
v]tebrae4 ,! orig9 ( ! p>ietals &       
frontals z pair$ bones 9 membrane       

re9=ces ?is conclusion4   ,section #cg4 
,b z c]ta9ly z we h no su* metam]ic     
segm5tation1 z ?is old] view implies1 9 
! bra9-case ( ! frog1 s q z c]ta9ly is  
metam]ic segm5tation evid5t 9 its       
bran*ial ar*es4 ,we h ! f\r gill slits (
 ! tadpole & _! b>s repeat+ "o ano!r2 ! 
hyoid b> 9 front ( ^! is evid5tly ( a   
simil> nature2 & t ! e> drum is d]iv$ f 
an imp]=ate gill slit is en=c$ by !     
pres5ce ( an op5 slit 7! spiracle7 9 !  
rays & dog-fi% 9 an entirely equival5t  
position4 ,does ! m\? answ] to a fur!r  
pair ( gill slits1 & is ! jaw ar*       
7palato-pt]ygoid  ,meckel's c>tilage7   
equival5t to ! ar*es t come beh9d x8    
,?is "q has be5 ask$1 & answ]$ 9 !      
affirmative1 by _m morphologi/s1 b n by 
any means by all4 ,! cranial n]ves h a  
curi\s simil>ity ( arrangem5t ) reg>d to
 ! gill slits & ! m\?2 ! fif? n]ve =ks  
ov] ! m\?1 ! sev5? =ks ov] ! e> drum1 ! 
n9?1 9 ! tadpole & fi%1 =ks ov] ! fir/  
bran*ial slit1 & ! t5? is1 z x 71 a lea%
 ( n]ves1 ea* =k+ ov] "o ( ! rema9+ gill

 slits4 ,b ?is matt] w be m intelligible
 :5 ! /ud5t has work$ ov] a fi% type1 & 
ne$ n deta9 u any fur!r n[4   ,section  
#ch4 ,see also ,section #ac aga91 9 :i* 
is ! sugge/ion t ! occipital "p ( !     
skull is possibly a fusion ( v]tebrae1 a
 new view ) mu* 9 its fav\r1 & obvi\sly 
an entirely diff]5t "o f ! old segm5tal 
view ( ! entire skull1 discuss$ 9       
,section #cf4   ,que/ions on ! ,frog    
,all ^! que/ions 7 actually set at      
,london ,univ]sity    ,exam9ations4 ,9  
,bo? ,editions4  #a4 ,give an acc\nt1 ) 
illu/rative sket*es1 ( ! dige/ive organs
 ( ! common frog1 specify+ p>ticul>ly ! 
diff]5t =ms ( epi!lium met ) 9 ! sev]al 
regions !re(4  #b4 ,describe ! he>t ( a 
frog1 & comp>e x ) t ( a fi% & ( a      
mammal1 m5tion+ 9 ea* case ! great      
vessels :i* op5 into ea* cavity4  #c4   
,comp>e ) "o ano!r ! brea?+ organs & !  
me*anism ( respiration 9 a frog & 9 a   
rabbit4 ,give figures %[+ ! condition ( 
! he>t & great art]ies 9 ^! animals1 &  
indicate 9 ea* case ! nature ( ! blood 9

 ! sev]al cavities ( ! he>t4  #d4 ,draw 
diagrams1 ) ! p>ts nam$1 illu/rat+ !    
arrangem5t ( ! *ief art]ies ( 7a7 !     
frog1 7b7 ! rabbit4 7c7 ,comp>e briefly 
! arrangem5ts ?us describ$4 7d7 ,9 :at  
important respects does ! vascul>       
me*anism ( ! frog diff] f t ( ! fi%1 9  
correlation ) ! pres5ce ( lungs8  #e4 ,9
 ! frog provid$1 free ! he>t1 bo? aortic
 ar*es1 dorsal aorta z f> z its t]m9al  
bifurcation1 & bo? *a9s ( sympa!tic     
ganglia f surr\nd+ /ructures2 & remove  
!m1 9 _! natural connection1 f ! animal 
into a wat*-glass4  #f4 ,describe ! male
 & female reproductive organs ( ! common
 frog1 & give "s acc\nt ( _! developm5t4
  #g4 ,describe1 ) figures1 ! bones ( ! 
limbs & limb-girdles ( a frog4  #h4     
,remove ! bra9 f ! frog provid$1 & place
 x 9 _s4 ,make a lett]$ draw+ ( its     
v5tral & dorsal surfaces4  #i4 ,po9t out
 ! correspond+ regions 9 ! bra9 ( a frog
 & a mammal1 & /ate :at are ! relations 
( ! ?ree prim>y bra9-vesicles to ^!     
regions4  #aj4 7a7 ,give an acc\nt1 )   

diagrams1 ( ! bra9 ( ! frog2 7b7 po9t   
out ! mo/ important diff]5ces betwe5 x &
 ! bra9 ( ! rabbit4 7c7 ,describe !     
sup]ficial orig9 & ! di/ribution ( !    
?ird1 7d7 ( ! fif?1 7e7 ( ! sev5?41 7f7 
( ! n9?1 & 7g7 ( ! t5? cranial n]ves ( !
 frog4  #aa4 ,describe1 ) figures1 !    
bra9 ( a frog1 & comp>e x ) t ( a       
rabbit4 ,:at d y "k conc]n+ ! functions 
( ! sev]al p>ts ( ! bra9 9 ! frog8  #ab4
 ,describe briefly ! fundam5tal         
prop]ties ( ! sp9al cord 9 ! frog4 ,by  
:at means w\ld y det]m9e :e!r a giv5    
n]ve is motor or s5sory8  #ac4 ,prep>e !
 skull ( ! frog provid$4 ,remove f x &  
place 9 glyc]9e on a glass slip !       
fronto-p>ietal & p>asph5oid bones4      
,label !m4 ,m>k on ! skull ) long ne$les
 & flag-labels ! sph5e?moid & ! pro-otic
 bones4  #ad4 ,comp>e ! skull ( ! rabbit
 & ! frog2 especially 9 reg>d to !      
atta*m5t ( ! jaw app>atus to ! cranium1 
& o!r po9ts :i* di/9ctly *>act]ize !    
high] z contra/$ ) ! l[] v]tebrata4     
#ae4 ,describe ! skeleton ( ! upp] & l[]

 jaw 7a7 9 ! frog1 7b7 9 ! rabbit4 ,po9t
 out exactly :at p>ts correspond ) "o   
ano!r 9 ! two animals comp>$4 7c7 ,:at  
bone 9 ! rabbit is g5]ally reg>d$ z     
correspond+ to ! quadrate c>tilage ( !  
frog8    -,! ,dog-,fi%  #a4 ,g5]al      
,anatomy  ,section #a4 ,9 ! dog-fi% we h
 a f> m antique type ( /ructure ?an 9   
any ( ! =ms we h hi!rto consid]$4 ,=ms  
closely relat$ to x occur among ! e>lie/
 rema9s ( v]tebrata t are to be f\nd 9 !
 geological record4 ,s9ce ! immeasurably
 remote ,silurian p]iod1 %>ks & dog-fi% 
h probably rema9$ )\t any ess5tial      
*anges ( condition1 & consequ5tly )\t   
any ess5tial *anges ( /ructure1 d[n to !
 pres5t day4 ,!n1 z n[1 !y dom9at$ !    
seas4 ,!y probably bran*$ (f f ! o!r    
v]tebrata be=e bone _h become abundant 9
 ! inn] skeleton1 :i* is consequ5tly 9  
_! case c>tilag9\s1 ) occasional        
calcification & no di/9ct bones at all4 
,unlike ! majority ( fi%1 !y possess no 
swimm+ bladd]-- ! precursor ( ! lungs2 b
 9 _m o!r respects1 notably 9 !         

uro-g5ital organs1 !y h1 9 common ) !   
high] v]tebrata1 pres]v$ features :i*   
may h be5 disguis$ or lo/ 9 ! p]fect+ ( 
su* mod]n & specializ$ fi% z1 = in/ance1
 ! cod1 salmon1 or h]r+4   ,section #b4 
,comp>+ ! g5]al build1 ( a dog-fi% ) t (
 a rabbit1 we notice ! abs5ce ( a di/9ct
 neck1 & ! g5]al conical =m2 ! pres5ce (
 a l>ge tail1 z consid]able1 at fir/1 9 
diamet] z ! h9d portion ( ! body1 & ( ! 
fir/ importance 9 progression1 9 :i*    
function ! f\r paddle-%ap$ limbs1 !     
lat]al f9s1 simply co-op]ate ) ! m$ian  
f9 along ! back = ! purpose ( /e]+2 &1 z
 a consequ5ce ( ! size ( ! tail1 we note
 also ! v5tral position ( ! ap]tures ( !
 body4 ,! anus1 & ur9>y & g5ital ducts  
unite 9 "o common *amb]1 ! cloaca4      
,beh9d ! head1 & 9 front ( ! =e f9      
7pectoral f971 are five gill slits      
7g4s47 lead+ f ! ph>ynx to ! ext]ior4 ,j
 beh9d ! eye is a small] & m dorsal op5+
 ( ! same k9d1 ! spiracle 7sp474 ,on !  
"u side ( ! head1 9 front ( ! m\?1 is ! 
nasal ap]ture 7olf471 ! op5+ ( ! nasal  

sac1 :i*1 unlike ! correspond+ organ ( !
 air-frequ5t+ v]tebrata1 has no int]nal 
n>ial op5+4 ,!re is1 h[ev]1 a groove    
runn+ f olf4 to ! corn] ( ! m\?1 & ?is1 
clos+1 9 ! v]tebrate types t live 9 air 
& are expos$ to incessant evaporation ( 
_! lubricat+ secretions1 con/itutes !   
primitive nasal passage4 ,! limbs are   
undiff]5tiat$ into upp]1 l[]1 & digital 
portions1 & are simply jo9t$1 flatt5$   
expansions4   ,section #c4 ,! sk9 ( !   
dog-fi% is closely set ) po9t$ too?-l   
scales1 ! placoid scales1 & ^! are      
cont9u$ ov] ! lips into ! m\? z tee?4   
,ea* scale consi/s ( a base ( true bone1
 ) a little tub]cle ( a h>d] sub/ance1  
d5t9e1 capp$ by a /ill d5s] cov]+1 !    
enamel4 ,! enamel is d]iv$ f ! out] lay]
 ( ! embryonic dog-fi%1 ! epibla/1 :i*  
also gives rise to ! epid]mis2 :ile !   
d5t9e & bony base arise 9 ! und]ly+     
mesobla/1 ! d]mis4 ,a mammalian too? has
 ess5tially ! same /ructure3 an out]    
coat ( enamel1 d]iv$ f epibla/1 ov]lies 
a mass ( d5t9e1 re/+ on bone1 b ! d5t9e 

is excavat$ int]nally1 to =m a          
pulpcavity conta9+ blood-vessels &      
n]ves4 ,mo/ l& animals1 h[ev]1 h tee?   
only 9 _! m\?s1 & h lo/ altoge!r !      
ext]nal tee? :i* con/itute ! arm\r ( !  
dog-fi%4 ,besides ! tee? !re p]haps     
rema9 relics ( ! placoid scales 9 !     
anatomy ( ! high] v]tebrata1 9 !        
membrane bones4 ,h[ placoid scales may h
 giv5 rise to ^! /ructures w be und]/ood
 by consid]+ su* a bone z ! vom] ( !    
frog4 ,?is bone lies on ! ro( ( ! frog's
 m\?1 & be>s a numb] ( d5ticles1 &      
altoge!r !re is a v /rong resemblance 9 
x to a numb] ( placoid scales ! bony    
bases ( :i* h become conflu5t4 ,9 !     
salam&]1 beh9d ! tee?-be>+ vom]s comes a
 simil> too!d p>asph5oid bone4 ,! same  
bone occurs 9 a correspond+ position 9 !
 frog1 b )\t tee?4 ,9 "s tail$          
amphibians ! vom]s & spl5ials are kn[n  
to arise by ! fusion ( small d5ticles4  
,^! facts seem to po9t to /ages 9 !     
fusion ( placoid bases1 & _! )drawal f !
 surface to become incorporat$ ) !      

cranial app>atus z membrane bones1 a    
process entirely complet$ 9 ! mammalian 
type4   ,section #d4 ,! alim5t>y canal (
 ! dog-fi%1 is a simple tube ?r[n into a
 ,z %ape4 ,! m\? is r\gh ) d5ticles1 &  
has a fle%y immovable tongue on its     
floor4 ,9 ! position ( ! ,eu/a*ian tube 
!re is a passage1 ! spiracle 7sp471     
runn+ out to ! ext]ior j ext]nal to !   
c>tilage conta9+ ! e>4 ,! ph>ynx        
communicates ) ! ext]ior ?r\gh five gill
 slits 7g4s471 & has1 ( c\rse1 no       
glottis or o!r lung op5+4 ,!re is a wide
 oesophagus pass+ into a ,u-%ap$ /oma*  
7/471 hav+1 l ! rabbit's1 ! sple5 7sp47 
on its out] curvature4 ,!re is no coil+ 
small inte/9e1 b ! %ort portion1 receiv+
 ! bile duct 7b4d47 & duct ( ! pancreas 
7pan471 is call$ ! duod5um 7d'dum474 ,! 
liv] has l>ge left 7,l4lv47 & "r lobes1 
& a m$ian lobe 7,m4lv471 9 :i* ! gall   
bladd] 7g4bl47 is emb$d$4 ,! next segm5t
 ( ! inte/9e is fusi=m1 conta9+ a spiral
 valve 7,figure #d71 ! %elf ( :i* po9ts 
/eeply =w>d2 x is sometimes call$ !     

colon 7co474 ,x is absorptive 9 function
 & probably repres5ts morphologically1 z
 x does physiologically1 ! great]       
portion ( ! small inte/9e4 ,a rectal gl&
 7r4g47 op5s f ! dorsal side into ! f9al
 portion ( ! canal 7rectum74   ,section 
#e4 ,! circulation pres5ts1 9 _m        
respects1 an approximation to ! /ate (  
affairs 9 ! develop+ embryos ( ! high]  
types4 ,! he>t 7,figure #c1 ,%eet -#ad- 
,error 9 ,fir/ ,edition #af7 is r\ghly1 
,z %ape1 & transmits only v5\s blood4 ,x
 lies 9 a cavity1 ! p]ic>dial cavity    
7,p4c4c471 cut (f by a p>tition f !     
g5]al coelome4 ,at "o po9t ?is p>tition 
is imp]fect1 & ! two spaces communicate 
?r\gh a p]ic>dio-p]itoneal canal        
7p4p4c471 :i* is also indicat$ by an    
arr[ 7p4p47 9 ! position & direction 9  
:i* ! /ud5t1 :5 dissect+1 %\ld ?ru/ 8   
seek]1 9 ,figure #a ,%eet #ae4 ,a s9us  
v5osus 7s4v4 9 ,figure #c1 ,%eet #af7   
receives ! v5\s trunks1 & c>ries ! blood
 ?r\gh a valve into ! baggy &           
transv]sely ext5d$ -auricle- atrium     

7au471 :5ce x passes into ! muscul>     
v5tricle 7,vn471 & !nce into ! truncus  
art]iosus4 ,?is truncus consi/s ( two   
p>ts3 ! fir/1 ! conus or pylangium      
7c4a471 muscul>1 contractile1 & conta9+ 
a s]ies ( valves2 ! second1 ! bulbus or 
synangium 7b4a471 )\t valves &          
pulsatile4 ,9 ! rabbit bo? s9us &       
truncus are abs5t1 or m]g$ 9 ! adjac5t  
p>ts ( ! he>t4   ,section #f4 ,f !      
bulbus !re bran*1 on ei!r side1 f\r     
art]ial trunks1 ! fir/ ( :i* =ks1 s t   
altoge!r !re are five aff]5t bran*ials  
7a4br47 tak+ blood to be a]at$ 9 !      
gills1 "h highly vascul> filam5t>y      
outgr[?s ( ! int]nal walls ( ! gill     
slits4     ,l9es f ,second ,edition     
only4    ,!re are altoge!r n9e vascul>  
outgr[?s 7demi-bran*s71 "o    on ea*    
wall ( ea* gill slit except ! la/1 on ! 
h9d wall (    :i* !re is none4 7,9 !    
spiracle is a m9iature demibran*1 !     
pseudo-bran*4 ,?is sugge/s t ! spiracle 
is really a some:at    modifi$ gill     
slit47  ,f\r eff]5t bran*ials 7e4br47   

c>ry ! a]at$ blood on to ! dorsal aorta 
7d4ao474 ,a c>otid art]y runs =w>d to ! 
head1 & a hypo-bran*ial art]y supplies !
 v5tral side ( ! ph>yngeal region4 ,!re 
are sub-clavian1 coeliac1 mes5t]ic1 &   
pelvic art]ies1 & ! dorsal aorta is     
cont9u$ ?r\gh ! l5g? ( ! tail z ! caudal
 art]y 7,cd4,a474   ,section #g4 ,a     
caudal ve9 7,cd4,v471 br++ blood back f 
! tail1 splits beh9d ! kidneys 7,k471 & 
=ms ! pair$ r5al portal ve9s 7r4p4v471  
break+ up into a capill>y sy/em 9 ! r5al
 organ4 ,a portal ve9 br+s blood f !    
inte/9es to ! liv]4   ,section #h4      
,in/ead ( be+ tubul> vessels1 ! *ief    
ve9s ( ! dog-fi% are1 9 _m cases1       
irregul> baggy s9uses4 ,?ree ma9 v5\s   
trunks fl[ into ! s9us v5osus4 ,9 !     
m$ian l9e f beh9d comes ! hepatic s9us  
7,h4,s472 & lat]ally1 f a dorsal        
direction1 ! ,cuvi]ian s9uses 7,c4,s47  
ent] x4 ,^!1 z ! /ud5t w pres5tly       
p]ceive1 are ! equival5ts ( ! rabbit's  
sup]ior cavae4 ,!y receive1 ne> _!      
conflu5ce ) ! s9us v5osus1 ! inf]ior    

jugul> ve9 7,i4,j4,v474 ,at _! dorsal   
orig91 !y are =m$ by ! meet+ ( ! ant]ior
 7,a4,c4,s47 & po/]ior 7,p4,c4,s47      
c>d9al s9uses4 ,! ant]ior c>d9al s9us   
-is1 r\ghly1 ! equival5t ( ! int]nal    
jugul> ve9-1 lies along dorsal to ! gill
 slits 7g4s471 & receives an orbital    
s9us f ! eye4 ,! po/]ior c>d9al s9us    
receives a sub-clavian ve9 7s4c4v47 & a 
lat]al ve9 7,l4,v471 & fuses po/]iorly )
 its fell[ 9 ! middle l9e4 ,?is m$ian   
fusion is a dep>ture f ! normal fi%     
type4 ,x mu/ n be confus$ ) ! inf]ior   
cava1 :i* is n f\nd 9 ! dog-fi%1 ! "r   
po/]ior c>d9als repres5t+ ! rabbit's    
azygos ve94 ,a simplifi$ diagram ( !    
circulation ( a fi% is giv5 9 ,figure   
#b1 ,%eet #af1 & ?is %\ld be c>efully   
comp>$ ) ! correspond+ small figure giv5
 ( ! vascul> sy/em ( our o!r types4     
,l9es f ,second ,edition only4    ,!    
blood ( ! dog-fi% resembles t ( ! frog4 
,section #i4 ,! int]nal skeleton1 z we h
 said1 is entirely c>tilag9\s1 & only ^?
 p>ts :i* are pre-=m$ 9 c>tilage 9 !    

skeletons ( ! high] types are repres5t$ 
"h4 ,! sp9al column consi/s ( two types 
( v]tebrae1 ! trunk1 be>+ %ort1 di/9ct1 
horizontally-project+ ribs 7r471 & !    
caudal4 ,! diagrams ( ,figure #e 7,%eet 
#ah7 are to illu/rate ! /ructure ( !    
c5trum ( a dog-fi% v]tebra2 ,c is a side
 view1 ,d a horizontal m$ian section1 ,a
 & ,b are transv]se sections at ! po9ts 
indicat$ by -,b & ,a- ,a & ,b           
respectively 9 ,figure ,c4 -7,by an     
un=tunate slip ( ! p5 9 ! figure1 ,a 0  
sub/itut$ = ,b2 section ,a corresponds  
to l9e ,b1 & vice v]sa47- ,! v]tebrae   
are holl[$ out bo? ant]iorly & po/]iorly
 7amphi-coel\s71 & a jelly-l noto*ord   
runs ?r\gh ! entire l5g? ( ! v]tebral   
column1 be+ con/rict$ at ! c5tres ( !   
c5tra1 & dilat$ betwe5 !m4 ,! neural ar*
 above ! c5trum1 & conta9+ ! sp9al cord1
 is made up ( neural plates 7n4p471 &   
int]neural plates 7i4n4p471 complet$    
above by a m$ian neural sp9e 7n4s474 ,9 
! caudal region1 in/ead ( ribs project+ 
outw>dly1 !re are haemal processes1     

incl9$ d[nw>ds & meet+ bel[1 =m+ an ar*1
 ! haemal ar*1 conta9+ ! caudal art]y & 
ve9-- ! ve9 v5tral to ! art]y-- &       
resembl+ ! neural ar*1 :i* conta9s !    
sp9al cord above1 9 %ape & size4        
,section #aj4 ,! pectoral limb & girdle 
7,figure #d1 ,%eet #af7 h only a v vague
 resemblance to ! correspond+ /ructures 
9 ! rabbit4 ,! girdle 7g47 is a         
transv]se b> ly+ v5tral to ! p]ic>dial  
wall1 & s5d+ up a portion 7sc471 dorsal 
to ! atta*m5t ( ! limb1 :i* answ]s to ! 
scapula & supra-scapula ( ! =ms above ! 
fi%4 ,?ree ma9 c>tilages1 nam$          
respectively ! pro- 7p4p471 meso-       
7m4p471 & meta-pt]ygium1 =m ! base ( !  
limb4 ,) ^!1 small] c>tilag9\s plates1  
rods1 & nodules articulate1 & =m a      
flatt5$ skeletal support = ! f94        
,section #aa4 ,! pelvic girdle & limb   
7,figure #b1 ,%eet #ae7 are simil> 9    
/ructure1 b ! pro-pt]ygium &            
meso-pt]ygium are abs5t1 & ! c>tilage   
answ]+ to ! meta-pt]ygium goes by ! "n (
 ! basi-pt]ygium4 ,9 ! male1 b n 9 !    

female1 ! pelvic f9s are unit$ beh9d !  
cloaca1 & !re are two /iff groov$       
copulatory organs1 ! clasp]s 7cl4 9     
,figure #a71 :i* h a c>tilag9\s support 
7cl4c474 ,^! clasp]s =m ! readie/ means 
( det]m9+ ! sex ( a specim5 be=e        
dissection4   ,section #ab4 ,! skull    
consi/s ( a c>tilag9\s cranium1 & ( jaw 
& visc]al ar*es4 ,! cranium p]si/s      
?r\gh\t life1 9 :at closely resembles a 
transitory embryonic condition ( ! high]
 types4 ,!re is a nasal capsule 7na4c471
 a bra9 case prop]1 & lat]al otic       
7auditory7 capsules 7ot4c47 conta9+ !   
int]nal e>4 7,?is %\ld be comp>$ ) !    
frog's embryonic skull47 ,! upp] jaw has
 a great b> ( c>tilage1 !               
palato-pt]ygoid1 z its sole support2 !  
ar* ( premaxilla1 maxilla1 jugal1 &     
squamosal-- all membrane bones-- is1 (  
c\rse1 n repres5t$4 ,9 ! frog ?is b> (  
c>tilage is jo9$ directly to ! otic     
capsule by a quadrate portion1 b ?is is 
only d\btfully repres5t$ 9 ! dog-fi% by 
a nodule ( c>tilage 9 ! pre-spiracul>   

ligam5t 7p4s474 ,! l[] jaw is support$1 
by ,meckel's c>tilage 7,m4,c474 ,! hyoid
 ar* consi/s ( two ma9 masses (         
c>tilage1 ! hyom&ibul> 7h4m471 & !      
c]atohyal 7c4h472 ! =m] ( ^! is tilt$   
slightly =w>d1 s t ! gill slit betwe5 x 
& ! jaw ar* is oblit]at$ bel[1 & !      
c>tilage comes to s]ve z ! int]m$i>y 9 !
 susp5sion ( ! jaw f ! otic mass4 ,!re  
are five bran*ial ar*es1 made up        
ph>yngo-1 epi- & c]ato-bran*ials1 & !   
v5tral elem5ts fuse 9 ! middle l9e to =m
 a common plate ( c>tilage4 ,outside ^! 
ar*es are c]ta9 small c>tilages1 ! extra
 bran*ials 7ex4b47 :i*1 toge!r ) c]ta9  
small labials by ! no/rils & at ! sides 
( ! gape1 probably repres5t /ructures ( 
consid]ably great] importance 9 t /ill m
 primitive fi%1 ! lamprey4 ,! deep      
groove figur$ lat]al to ! otic capsule  
is ! connect+ l9e ( ! orbital & ant]ior 
c>d9al s9uses2 ! outl9e ( ! ant]ior     
c>d9al s9us 9 ?is figure & 9 ,figure #a 
is r\ghly indicat$ by a dott$ l9e4      
,section #ac4 ,figure #c;a is a r\gh    

diagram ( ! int]nal e>-- ! only auditory
 /ructure ( our type 7comp>e ,rabbit1   
,%eet #g74 ,to dissect out ! auditory   
labyr9? )\t injury is a difficult       
p]=mance1 b its /ructure may be made out
 v satisfactorily by p>+ away successive
 slices ( ! otic mass4 ,su* a section is
 %[n by ,figure #c;b2 ?r\gh ! transluc5t
 hyal9e c>tilage ! utriculus &          
horizontal canal c be d>kly se54 ,!     
ductus endolymphaticus 7vide ,rabbit7 is
 indicat$ by a dott$ l9e 9 our figure4  
,x is situat$ int]nal to ! "r-angle     
betwe5 ! two v]tical canals1 & rea*es to
 ! surface ( ! otic capsule4   ,section 
#ad4 ,! bra9 %[s ! ?ree prim>y vesicles 
mu* m di/9ctly ?an d our high] types4 ,!
 =e-bra9 has l>ge lat]ally sep>at$      
olfactory lobes 7rh471 !re are          
relatively small hemisph]es 7pr4c471 !  
/alk ( ! p9eal gl& tilts =w>d1 & ! gl&  
itself is mu* ne>] ! surface1 be+ emb$d$
 9 ! c>tilage ( ! bra9 case1 & !        
pituit>y body is relatively v l>ge1 &   
has lat]al vascul> lobes on ei!r side4  

,foll[+ ! usual int]pretation ( ! p>ts1 
we f9d optic lobes 7op4l47 z ! ro( ( !  
mid-bra91 & beh9d a v l>ge1 m$ian1      
holl[1 tongue-%ap$ c]ebellum 7c4b474 ,! 
m$ulla is l>ge1 & c]ta9 lat]al re/i=m   
tracts 7r4t47 !re91 :i* also occur 9 !  
high] types1 are "h exceptionally       
conspicu\s4   ,section #ae4 ,! dog-fi%  
has t5 pairs ( cranial n]ves1           
correspond+ to ! ant]ior t5 ( ! rabbit v
 closely1 :5 we all[ = ! modification ! 
latt] has suff]$ ?r\gh ! conv]sion ( "s 
"p ( ! spiracul> cleft to an e>drum1 & !
 oblit]ation ( ! po/-hyoid bran*ial     
slits4  ,! fir/ & second n]ves are      
really bra9 lobes1 & n]ves ( ! special  
s5ses ( smell & sight respectively4  ,! 
?ird 7oculomotor71 ! f\r? 7pa!ticus71 & 
! six? 7abduc5s7 are di/ribut$ to       
exactly ! same muscles ( ! eyeball z !y 
are 9 ! rabbit4  ,! fif? n]ve1 has1 9 ! 
dog-fi%1 z 9 ! rabbit1 ?ree *ief        
bran*es4 ,v4#b & ,v4#c =k ov] ! m\? j z 
!y d 9 ! mammal2 ,v4#a passes out ( !   
cranium by a sep>ate & m dorsal op5+1 & 

runs along a groove along ! dorsal      
int]nal wall ( ! orbit1 imm$iately b5ea?
 a simil> bran* ( ,,vii41 :i* is n      
di/9ct 9 ! rabbit4 ,! grooves are %[n 9 
! figure ( ! cranium1 ,%eet #ah2 ! jo9t 
n]ve ?us comp\nd$ ( ,v4 & ,,vii4 is     
call$ ! oph?almic 7oph474 ,x is         
di/ribut$ to ! sk9 above ! nose & orbit4
 ,:5 ! /ud5t comm5ces to dissect ! head 
( a dog-fi% he notices ov] ! dorsal     
surface ( ! sn\t an exudation ( a       
yell[i% jelly-l sub/ance1 & on remov+ ! 
t\gh sk9 ov] ?is region & ov] ! c5tre ( 
! skull he f9ds1 ly+ b5ea? x1 a quantity
 ( coil+ simple tubuli full ( su*       
yell[i% matt]4 ,^! tubuli op5 on !      
surface by small pores1 & ! n]ves       
t]m9ate 9 hair-l extremities 9 _! l9+4  
,^! s5se tubes are peculi> to aquatic   
=ms2 alli$ /ructures are f\nd ov] ! head
 & along a lat]al l9e 7see bel[7 9 !    
tadpole1 b :5 ! frog em]ges f ! wat] !y 
are lo/4 ,!y1 d\btless1 indicate "s     
unkn[n s5se entirely beyond our         
exp]i5ce1 & ei!r only possible or only  

necess>y :5 ! animal is subm]g$4  ,9    
addition to ! oph?almic moiety m5tion$  
above1 ! sev5? n]ve has a vidian bran*  
7vid47 runn+ ov] ! ro( ( ! m\?1 &       
besides ?is its ma9 bran*es =k ov] !    
spiracle1 j z ,v4 =ks ov] ! m\?1 & z    
,,ix4 & ,x4 =k ov] gill clefts4 ,?is    
n]ve 9 ! rabbit is evid5tly consid]ably 
modifi$ f ?is m primitive condition4  ,!
 eigh? is ! auditory n]ve1 z 9 ! rabbit4
  ,! n9? n]ve =ks ov] ! fir/ bran*ial   
cleft4  ,! t5? n]ve is easily expos$ by 
cutt+ d[n ?r\gh ! body wall muscles ov] 
! gill clefts1 into ! ant]ior c>d9al    
s9us 7,a4,c4,s474 ,x gives (f 7a7       
bran*es =k+ ov] ! po/]ior f\r gill      
slits1 7b7 a great lat]al n]ve runn+    
inw>d1 & back ?r\gh ! body-wall muscle1 
& connect$ ) a l9e ( s5se organs simil> 
to ^? 9 ! head1 ! lat]al l9e1 & 7c7 a   
visc]al n]ve curv+ r\nd to ! oesophagus 
& /oma*4 ,9 dissection x becomes v      
evid5t t ! t5? n]ve is really a lea% (  
n]ves1 ea* "o equival5t to ! n9?4  ,we  
may "h call ! att5tion ( ! read] to !   

fact ( ! s+ul> resemblance ( ,v41       
,,vii41 ,,ix41 & ! factors ( ,x4 ,t ea* 
has a v5tral =k1 we h already notic$4   
,ea* also 78,,ix47 has a dorsal         
con/itu5t connect$ ) ! s5se organs ( !  
sk94 ,! vidian bran* ( ,,vii41 h[ev]1 is
 n evid5tly repres5t$ 9 ! o!rs4         
,section #af4 ,! coelom ( ! dog-fi% is  
peculi>-- among ! types we treat (-- 9 !
 possession ( two direct communications 
) ! ext]ior1 9 addition to ! cu/om>y    
indirect way ?r\gh ! oviduct4 ,^! are ! 
abdom9al pores 7a4p47 on ei!r side ( !  
cloaca 9 ei!r sex4 ,!y c always be      
readily demon/rat$ by prob+ out f ! body
 cavity1 9 ! direction indicat$ by !    
arr[ 7a4p47 9 ,figure #a1 ,%eet #ae4 ,!y
 probably s]ve to equalize ! int]nal &  
ext]nal pressure ( ! fi% z x *anges its 
dep? 9 ! wat]1 j z ! ,eu/a*ian tubes    
equalize ! pressure on ei!r side ( !    
mammal's tympanic membrane4   ,section  
#ag4 ,! musculature ( ! dog-fi% body is 
cut into ,v-%ap$ segm5ts1 ! po9t ( ! ,v 
be+ direct$ =w>d4 ,! segm5ts alt]nate ) 

! v]tebrae1 & are call$ myom]es4 ,su* a 
segm5tation is evid5t1 ?\gh less m>k$1 9
 ! body wall muscles ( ! frog1 & 9 !    
abdom9al musculature ( ! rabbit & o!r   
mammals x is /ill to be trac$4          
,section #ah4 ,! uro-g5ital organs ( !  
female dog-fi% 7,figure #a1 ,%eet #ag7  
consi/ ( an unpair$ ov>y 7ov471 pair$   
oviducts 7o4d471 enl>g$ at "o po9t to =m
 an oviducal gl& 7o4d4g471 kidneys 7k471
 ) uret]s 7ur47 unit+ to =m a ur9>y s9us
 7u4s47 op5+ into ! cloaca by a m$ian   
ur9>y papilla sep>ate f ! oviducal      
op5+s4 ,! eggs conta9 mu* yolk1 &1 l ^? 
( ! f[l1 are v l>ge2 l ! f[l1 too1 "o ( 
! ov>ies is suppress$1 & x is ! "r ov>y 
t alone rema9s4 ,! two oviducts meet 9  
front ( ! liv] v5tral to ! oesophagus1 &
 h !re a common op5+ by :i* ! ova are   
receiv$ aft] be+ %$ into ! body cavity4 
,! eggs receive an oblong horny case 9 !
 oviduct2 9 ! figure su* a case is      
figur$ z di/5d+ ! duct at e4 ,! te/es ( 
! male 7,t4 9 ,figure #b7 are p>tially  
conflu5t 9 ! middle l9e4 ,!y communicate

 ?r\gh vasa eff]5tia 7v4e47 ) ! modifi$ 
ant]ior "p ( ! kidney1 ! epididymis     
7ep471 f :i* ! vas def]5s 7v47 runs to !
 m$ian uro-g5ital s9us 7u4g4s471 into   
:i* ! uret]s 7ur47 also op54 ,! silv]y  
p]itoneum 7l9+ ( ! body cavity7 cov]s   
ov] ! r$di% kidneys1 & hides !m 9       
dissection4   ,section #ai4 ,figure #c1 
,%eet #ag1 is a g5]aliz$ diagram ( !    
uro-g5ital organs 9 ! v]tebrata2 ,m4,l4 
is ! middle l9e ( ! body1 ,g4 is !      
g5ital organ1 ,pr4 is ! pronephros1 or  
=e kidney1 a /ructure :i* is nev]       
develop$ 9 ! dog-fi%1 b :i* has         
functional importance 9 ! tadpole & cod1
 & appe>s z a transitory rudim5t 9 !    
*ick4 ,a duct1 :i* is (t5 spok5 ( z !   
pronephric duct 7p4d471 & :i* we h      
figur$ "u t "n1 is always develop$4     
,ant]iorly x op5s into ! body cavity4 ,x
 is also call$ ! ,mull]ian duct1 & 9 !  
great majority ( v]tebrata x becomes !  
oviduct1 unit+ ) its fell[1 9 ! case ( !
 dog-fi%1 v5tral to ! oesophagus4 ,9 !  
male x usually disappe>s2 ! ut]us       

mascul9us ( ! rabbit is /ill v g5]ally  
reg>d$ z a ve/ige ( x4 ,kollik] has %[n1
 h[ev]1 t ?is int]pretation is          
improbable4 ,ms4 is ! mesonephros1 "s or
 all ( :i* becomes ! epididymis 9 ! male
 ( types possess+ t organ1 & is connect$
 ) ,g4 by ! vasa eff]5tia4 ,mt41 !      
metanephros1 is1 9 -actual fact- ! frog1
 indi/+ui%ably cont9u\s ) ,ms41 & is !  
functional kidney1 its duct 7metanephric
 duct7 be+ ei!r undiff]5tiat$ f !       
mesonephric 7z is ! case ) ! frog7 or   
l>gely split (f f x1 z 9 ! dog-fi%1 to  
=m ! uret]4   ,section #bj4 ,!          
correspond5ce ( ! male organs ( !       
dog-fi% ) ^? ( ! rabbit1 w be m evid5t  
if ! /ud5t imag9e--     7a7 ! te/es1    
vasa eff]5tia1 & epididymis ( ea* side  
to    %ift po/]iorly until !y rea* a    
position on ei!r side (    ! cloaca2 &  
7b7 ,! uro-g5ital ap]tures1 in/ead (    
meet+ dorsally &    po/]iorly to ! anus1
 to %ift r\nd t op5+ & meet    ant]iorly
 & v5trically to x4   ,section #ba4 ,?is
 completes our survey ( ?is type4       

,except :]e we h specifi$ diff]5ces1 !  
g5]al plan ( its anatomy foll[s ! l9es (
 ! o!r v]tebrate types describ$4        
,que/ions on ! ,dog-,fi%  #a4 ,describe 
! alim5t>y canal ( ! dog-fi%1 & comp>e x
 ) t ( ! rabbit 9 detail4  #b4 ,comp>e !
 coelom ( ! dog-fi% & rabbit4  #c4 ,draw
 diagrams to illu/rate ! c\rse ( !      
circulation 9 ! dog-fi%4  #d4 7a7       
,describe fully ! he>t ( a dog-fi%4 7b7 
,comp>e x ) t ( a rabbit4  #e4 ,give an 
acc\nt ( ! respiratory app>atus ( !     
dog-fi%4  #f4 ,draw diagrams ( a dog-fi%
 v]tebra1 & comp>e ! c5trum ) t ( a     
rabbit4  #g4 ,comp>e ! v]tebral column (
 ! dog-fi% & rabbit4  #h4 ,draw diagrams
 ( ! limbs & limb-girdles ( ! dog-fi%4  
,comp>e ! pectoral ) ! pelvic f94  #i4  
,draw diagrams ( 7a7 ! male & 7b7 !     
female urog5ital organs ( ! dog-fi%4 7c7
 ,comp>e !m c>efully ) ^? ( ! rabbit4   
#aj4 ,comp>e ! circulation 9 ! kidney ( 
dog-fi% & rabbit4  #aa4 ,give an acc\nt 
( ! cranio-facial app>atus ( ! dog-fi%4 
,/ate cle>ly :at repres5tation ( ?is    

occurs 9 ! frog & 9 ! rabbit4  #ab4     
,give draw+ 7a7 f above1 7b7 f ! side1 (
 ! dog-fi% bra94  #ac4 ,/ate ! orig9 & !
 di/ribution ( ! fif?1 sev5?1 n9?1 & t5?
 cranial n]ves 9 ! dog-fi%4  #ad4       
,comp>e1 "o by "o1 ! cranial n]ves ( !  
dog-fi% ) ^? ( any high] v]tebrate1 z   
reg>ds _! orig9 & _! di/ribution4  #ae4 
,describe ! auditory organ ( ! dog-fi%4 
,:at p>ts are add$ to ?is 9 ! high]     
type8  #af4 ,draw ! cloaca 7a7 ( a male1
 7b7 a female dog-fi%4  #ag4            
7,practical47 ,demon/rate 9 a dog-fi% ! 
pa!tic n]ve1 ! op5+ betwe5 p]ic>dium &  
coelom4 ! abdom9al pores1 & ! uret]4    
-,amphioxus  #a4 ,anatomy  ,section #a4 
,we f9d 9 ,amphioxus ! ess5tial         
v]tebrate features r$uc$ to _! simple/  
expression &1 9 addition1 some:at       
di/ort$4 ,!re are wide diff]5ces f t    
v]tebrate plan ) :i* ! read] may n[ be  
consid]$ famili>4 ,!re are no limbs4    
,!re is an unbrok5 f9 along ! m$ian     
dorsal l9e & com+ r\nd along ! v5tral   
middle l9e = ab\t half ! animal's l5g?4 

,b two l[ly v]tebrates1 ! hag-fi% &     
lamprey1 h no limbs & a cont9u\s f94    
,!re is1 z we %all see m cle>ly1 a      
/ructure1 ! respiratory atrium1 n       
app>5tly repres5t$ 9 ! true v]tebrate   
types1 at lea/ 9 _! adult /ages4 ,!re is
 no di/9ct he>t1 only a debateable bra91
 q )\t ! typical division into ?ree     
prim>y vesicles1 no skull1 no /ructures 
:atev] ( c>tilage or bone1 no g5ital    
ducts1 no kidneys at all resembl+ ^? ( !
 v]tebrata1 no pancreas1 no sple52      
app>5tly no sympa!tic *a91 no pair$ s5se
 organs1 eyes1 e>s1 or nasal sacs1 9 all
 ( :i* po9ts we h /rik+ diff]5ces f all 
true v]tebrata2 & su* a *>act]i/ic      
v]tebrate peculi>ity z ! p9eal gl& we c 
only say is repres5t$ v d\btfully by !  
eye spot4   ,section #b4 ,! v]tebral    
column is devoid ( v]tebrae2 x is       
?r\gh\t life a rod ( gelat9\s tissue1 ! 
noto*ord 7,figure #a1 n4c471 surr\nd$ by
 a cellul> %ea?4 ,su* a rod is precursor
 to ! v]tebral column 9 ! true          
v]tebrates1 b1 except 9 su* l[ly =ms z !

 lamprey1 is usually replac$1 p>tially  
7e4g41 dog-fi%7 or :olly 7z 9 ! rabbit7 
by at fir/ c>tilag9\s v]tebrae ^: bodies
 are d]iv$ f its %ea?4 ,fur!r1 :ile 9   
all true v]tebrata ! noto*ord ( !       
develop+ "y rea*es ant]iorly at mo/ to !
 mid-bra91 & is !re at its t]m9ation    
enclos$ by ! middle portion ( ! skull1 9
 ,amphioxus x rea*es f> 9 front ( !     
ant]ior extremity ( ! n]v\s sy/em1 to ! 
end ( ! animal's body499 ,on ?is acc\nt 
! foll[+ classification is sometimes    
made ( ^? animals :i* h a noto*ord3--   
-,*ordata 7 ,v]tebrata1 z us$ by        
,lanke/]74        #a4 ,hav+ ! noto*ord  
rea*+ 9 front ( ! bra94                 
,cephalo*orda  ,amphioxus4        #b4   
,hav+ ! noto*ord rea*+ ant]iorly to !   
mid-bra91 a       bra9 ( ?ree prim>y    
vesicles & a skull4       ,craniata  all
 true v]tebrata3 fi%es1 amphibia1       
reptiles1       birds1 & mammals        
7,v]tebrata ( ,balf\r74        #c4 ,hav+
 ! noto*ord conf9$ to ! tail4           
,uro*orda  ! ascidians1 or sea-squirts1 

c]ta9 =ms ( life       only rec5tly     
recognis$ z relatives ( ! v]tebrata4  99
 ,! ant]ior end ( ! noto*ord 9 !        
develop+ rabbit or dog lies :]e ! middle
 ( ! basisph5oid bone is de/9$ to be4   
,section #c4 ,figure #a1 ,%eet #ai1 %[s 
! g5]al anatomy ( ,amphioxus4 ,we       
recognise f\r important po9ts (         
resemblance to ! e>li] phases ( ! high] 
& ! p]man5t /ructure ( ! l[] memb]s ( ! 
v]tebrata1 & x is ^! t ju/ify !         
inclusion ( amphioxus 9 ?is volume4 ,9 !
 fir/ place !re is !--     -,noto*ord4  
,9 ! next1 j above x 7at s4c47 we f9d-- 
-,a ,dorsal ,tubul> ,n]v\s ,axis1    !  
sp9al cord4 ,?irdly1 ! ph>ynx 7ph47 is  
p]=at$ by--     -,respiratory ,slits1   
?\gh ^!1 in/ead ( be+ /raight sla%es1   
are modifi$ f    a ,u-%ape slant v mu*  
=w>d & are mu* m num]\s ?an    9 any    
true v]tebrate44 -,&-1 ,f\r?ly1 !re is1 
z we %all    see1 a--     -,v]tebrate   
,type ( ,circulation4    ,& f9ally !    
body-wall muscles are divid$ into--     
-,myom]s4   ,section #d4 ,! alim5t>y    

canal ( ,amphioxus comm5ces ) an oral   
cavity1 n repres5t$ 9 our v]tebrata1    
surr\nd$ by a numb] ( cirri1 or         
t5tacles1 support$ by a horny sub/ance  
:i* seems to be *it91 a common skeletal 
mat]ial among inv]tebrates4 ,a velum    
7v47 =ms a curta91 p]=at$ by ! m\? & by 
two small] hyoidean ap]tures1 betwe5 !  
oral cavity & ! ph>ynx 7ph474 ,ph>yux is
 "h us$ 9 a wid] s5se ?an 9 ! true      
v]tebrata2 x rea*es back close to !     
liv]1 & is !re=e equival5t to ph>ynx    
oesophagus  a portion or all ( ! /oma*4 
,! s-call$ hyoidean ap]tures are n      
equival5t to ! simil>ly-nam$ p>ts ( !   
v]tebrata4 ,beh9d ! ph>ynx ! inte/9e    
7int47 runs /raight out to ! anus 7an471
 :i* op5s n 9 ! middle l9e1 z "o might  
expect1 b 9 ! left side6 ,! liv] lies   
usually on ! creature's "r1 & in/ead (  
be+ a compact gl&1 is simply bag-l4     
,section #e4 ,! circulation is peculi>ly
 r$uc$ 7,figure #b74 ,! c>diac aorta    
7c4ao47 lies along ! v5tral side ( !    
ph>ynx1 & s5ds bran*es up along !       

complete b>s betwe5 ! gill slits4 ,!re  
is no -di/9ct- he>t1 b ! :ole ( ! c>diac
 aorta is contractile1 & at ! bases ( ! 
aortic ar*es t run up ! b>s !re are     
contractile dilatations t assi/ 9 !     
propulsion ( ! blood4 ,dorsal to !      
ph>ynx1 z 9 fi%es1 !re is a pair (      
dorsal aorta 7d4ao47 t unite above !    
liv] 7comp>e ! frog1 = in/ance71 & !nce 
run backw>d z a m$ian dorsal aorta      
7d4ao4'74 ,a portal ve9 7p4v47 br+ blood
 back f ! inte/9e 7& app>5tly f ! :ole  
po/]ior portion ( ! animal7 to ! liv]4  
,!nce hepatic ve9s 7hep47 take x to !   
c>diac aorta4     ,l9es f ,fir/ ,edition
 only4    -,:5 we rememb] t 9 !         
embryonic v]tebrate ! he>t is at    fir/
 a /raight tube1 ?is circulation appe>s 
ev5 m /rik+ly    v]tebrate 9 its "* ?an 
be=e4-   ,section #f4 ,! coelom1 or body
 cavity1 ( ,amphioxus lies1 ( c\rse1 z 9
 ! v]tebrata1 betwe5 ! inte/9al wall & !
 body walls1 &1 j z 9 ! v]tebrata1 x is 
l>gely r$uc$ :]e gill slits occur4 ,b   
matt]s are r complicat$ by ! pres5ce (  

an atrial cavity r\nd ! ph>ynx1 :i* is n
 c]ta9ly repres5t$ 9 ! v]tebrata1 & :i* 
! /ud5t is at fir/ apt to call ! body   
cavity1 al?\gh x is entirely di/9ct &   
diff]5t f t space4 ,! mutual relation ( 
! two w become app>5t aft] a /udy (     
,figures #aj1 #aa1 #ab 7,%eet #ba74     
,figure #aj gives diagrammatically a    
section ( a v "y /age ( ,amphioxus2 ,p  
is ! ph>ynx portion ( ! alim5t>y canal1 
coe4 is ! coelom surr\nd+ x at ?is /age 
"h z else:]e2 mt4c4 are c]ta9 lymph     
spaces1 ! metapleural canals1 betwe5 :i*
 a small invag9ation 7i4e41 a pu%+-971  
at41 ( ! out] epid]mis occurs2 n4c4 is !
 noto*ord1 & s4c4 ! sp9al cord4 ,! gill 
slits1 by :i* ,p4 communicates ) !      
ext]ior1 are n %[n4 ,next ,figure #aa   
%[s ! invag9ation 7at47 pu%+ its way 91 
& cut (f f ! ext]ior by a meet+ ( ! body
 wall bel[4 ,note t at4 is a portion ( !
 animal's ext]ior ?us embrac$ by its    
body1 & t its l9+ is !re=e ( ! same     
mat]ial z ! ext]nal integum5t4 ,9       
,figure #ab1 at4 is develop+ upw>d1 s t 

! true body hangs into x4 ,n[ imag9e !  
gill slits p]=at$1 z %[n by !           
d\ble-head$ arr[ 9 ,figure #ab4 ,figure 
#c1 on ,%eet #bj1 is a less diagrammatic
 repres5tation ( a cross-section ( !    
ph>yngeal region 7vide ,figure #a1 ,%eet
 #ai74 ,! /ud5t %\ld comp>e ,figure #c1 
,%eet #bj1 & ,figure #ab1 ,%eet #ba4 ,! 
atrium & metapleural canals are easily  
recognis$ 9 bo?4 ,9 ,figure #c ! coelom 
is mu* cut up by ! gill slits1 & we h   
rema9+ ( x 7a7 ! dorsal coelomic canals 
7d4c4c47 & 7b7 ! bran*ial canals 7br4c47
 9 ! b>s betwe5 ! slits4 ,! atrial      
cavity rema9s op5 to ! ext]ior at "o    
po9t1 ! atrial pore 7at4p474   ,section 
#g4 ,! me?od ( exam9+ cross-sections is 
an extremely conv5i5t "o 9 ! /udy ( su* 
a type z ,amphioxus4 ,! /ud5t %\ld v    
c>efully g ov] & copy ! six sections on 
,%eet #bj1 comp>+ ,figure #a z he goes4 
,he %\ld d ?is be=e read+ :at foll[s4   
,"o little matt] mu/ be borne 9 m9d4 ,^!
 figures are m]ely int5d$ to convey !   
great /ructural ideas1 & !y are         

consid]ably simplifi$2 !y mu/ n be      
reg>d$ z a sub/itute = ! exam9ation (   
microscopic sections4 ,he w notice a    
numb] ( r\nd$ masses f ! body wall4 ,!  
-,= in/ance1 ! body-wall- muscles (     
,amphioxus are arrang$ 9 bundles b5t    
%>ply 9 an arr[ %ape1 ! po9t =w>d4 -,a  
numb] ( ^! bundles are cut 9 any "o     
section1 & s ! ev5 %ad+ ( our diagrams1 
if !y pr(ess$ to be any?+ m ?an         
diagrams1 %\ld be brok5 up into masses4-
 ,^! -bundles1 we may m5tion-1 are call$
 myom]es1 & !y are indicat$ 9 ,figure #a
 by l9es po9t+ acutely =w>d4 ,sev]al are
 consequ5tly cut 9 any transv]se section
 7,%eet #bj71 & ^! are ! r\nd$ masses he
 sees4 ,simil> myom]es1 simil>ly        
situat$1 are f\nd 9 fi%1 beh9d ! head1  
&1 less obvi\sly1 !y occur ) dim9i%+    
importance z ! scale ( ! v]tebrata is   
asc5d$4   ,section #h4 ,if we comp>e !  
n]v\s sy/em ( amphioxus ) t ( any       
v]tebrate1 we f9d at once a numb] (     
/rik+ diff]5ces4 ,9 ! fir/ place1 !     
skeletal cov]+ ( x1 ! cranium & ! neural

 ar*es ( v]tebrae1 are repres5t$ only by
 a greatly simplifi$ connective tissue4 
,9 ! next1 a simple & slight ant]ior    
dilatation alone repres5ts ! bra94 ,a   
pat* ( black pigm5t ant]ior to ?is      
7e4s47 may or may n be :at its "n       
implies an eye-spot4 ,!re is a ciliat$  
funnel1 c4f4 7,figure #a1 ,%eet #ai71   
op5+ on ! left side1 :i* has be5 assum$ 
to be olfactory 9 its functions1 & 9 !  
m\? *amb] a ciliat$ pit 7c4p471 :i* may1
 or may n1 be an organ ( ta/e4 ,! v5tral
 fissure ( ! sp9al cord is abs5t4 ,!    
dorsal n]ves are )\t ganglia1 & d n come
 (f 9 pairs1 b alt]nately1 "o to ! left1
 !n "o to ! "r1 "o to ! left1 "o to !   
"r1 & s on4 ,! v5tral n]ves are v %ort1 
m num]\s ?an ! dorsal1 & nev] unite ) ^!
 latt] to =m mix$ n]ves4  ,! /ud5t w    
obs]ve t "h1 j z 9 ! case ( ! ciliat$   
funnel & anus1 ! ,amphioxus is n /rictly
 symmetrical1 b twi/$1 z x 71 & s dep>ts
 f ! g5]al rule ( at lea/ ext]nal       
bilat]al symmetry obta9+ among !        
v]tebrates4 ,x habitually lies on "o    

side 9 ! mud ( ! sea bottom1 & x is     
probable t ?is ext]nal asymmetry is due 
to ?is habit1 s t too mu* classificatory
 importance mu/ n be atta*$ to x4 ,!    
soles & o!r relat$ fi%1 = in/ance1 are  
twi/$ & asymmetrical1 ?r\gh a simil>    
specific habit1 to su* an ext5t t bo?   
eyes lie on "o side ( ! animal4         
,section #i4 ,no kidney on ! v]tebrate  
patt]n is f\nd1 b ! foll[+ /ructures h1 
among o!rs1 be5 sugge/$ z r5al organs3--
     7a7 ,c]ta9 canals1 ! br[n tubes (  
,lanke/] 7b4t4,l41 ,figure #b1    ,%eet 
#ai71 a pair ( pigm5t$ tubes op5+ into !
 atrium at !    h9d end ( ! ph>ynx1 ly+ 
=w>d along by ! dorsal coelomic         
canals1 & hav+ an int]nal op5+ also4    
7b7 ,c]ta9 tubuli describ$ by ,weiss z  
situat$ 9 a s]ies along    ! upp] corn]s
 ( ! atrial cavity1 & communicat+1 aft] 
!    fa%ion1 ( ! nephridia ( ! e>?worm1 
) ! coelom & )    ! ext]ior 7or1 r1 ) t 
portion ( ! animal's ext]ior    enclos$ 
9 by ! atrial wall2 comp>e ,section #f74
     7c7 ,! g5]al epi!lial l9+ ( !      

atrium4  ,! reproductive organs 7,figure
 #d1 ,%eet #bj1 g47 are masses ( cells  
situat$ 9 an isolat$ "p ( ! coelom 9 !  
atrial folds1 &1 hav+ no ducts1 _!      
cont5ts mu/ escape into ! atrium by     
rupture ( ! body-wall4 ,!nce !y escape  
ei!r by gill-slits1 ph>ynx & m\?1 or1 m 
g5]ally1 ?r\gh ! atrial pore4 ,!        
animals1 l all ! v]tebrata1 are         
dioeci\s1 i4e41 male or female4         
,section #aj4 ,! endo/yle 7end471 9     
,figures #c & #d1 is a ciliat$ pa? or   
groove on ! "u side ( ! ph>ynx1 :i* is  
g5]ally suppos$ to repres5t ! ?yroid gl&
 ( v]tebrates4 ,! v]tebrate ?yroid1 e>ly
 9 developm5t1 is c]ta9ly an op5 & long 
n>r[ groove 9 ! v5tral side ( ! ph>ynx4 
,! hyp]-ph>yngeal groove 7h4p47 has be5 
9 ! pa/ comp>$ to ! pituit>y body1 b !re
 is little d\bt n[ t ?is /ructure is    
repres5t$ by ! ciliat$ pit4   ,section  
#aa4 ,! /ud5t is advis$ to revise ?is   
*apt] be=e proce$+1 & to s*$ule c>efully
 ! anatomical features "u ! head+s (    
7#a47 di/9ctly v]tebrate *>act]s1 7#b47 

*>act]s contra/+ ) ! normal v]tebrate   
/ructure1 7#c47 facts ( d\btful import1 
) ! sugge/ions giv5 9 ! text writt5     
aga9/ !m4    #b4 ,! ,developm5t (       
,amphioxus  ,section #ab4 ,! developm5t 
( amphioxus1 /udi$ completely1 is at    
once "o ( ! mo/ allur+ & difficult tasks
 9 ! way ( ! zoologi/2 b c]ta9 ( its    
e>li] & mo/ obvi\s fa/s may v conv5i5tly
 be tak5 into consid]ation n[4  ,section
 #ac4 ,! ph5om5a ( ! extrusion ( pol>   
bodies & f]tilization are treat$ ( lat]1
 & w1 !re=e1 n be consid]$ n[4 ,we w />t
 our description ) an egg-cell1 :i* has 
escap$1 ( c\rse1 s9ce !re are no g5ital 
ducts1 by rupture ( ! p>5t1 has be5     
f]tiliz$ by ! male elem5t1 & is ab\t to 
develop into a "y amphioxus4 ,x is      
simply a s+le cell1 ) "s p[] ( amoeboid 
motion1 a s+le nucleus & nucleolus2 & 9 
amphioxus its protoplasm is cle> &      
transp>5t4 ,frequ5tly ova are load$ )   
granules ( food /ore 7yolk71 :i* enable 
! "y animal to g f> ) its developm5t    
be=e x is hat*$ & has to beg9 f5d+ =    

itself4 ,su* an ovum z t ( our pres5t   
type1 h[ev] be+ devoid ( su* yolk       
7aleci?al  )\t yolk71 necessitates a v  
e>ly />t 9 life1 &1 = reasons too       
complicat$ to /ate fully "h1 !          
developm5t 9 su* a case is consid]$     
p>ticul>ly in/ructive & primitive by    
zoologi/s4   ,section #ad4 ,! fir/ ?+ to
 be se5 9 ! develop+ cell is a deep5+   
circul> groove 7,figure #a1 ,%eet #ba71 
:i* divides ! ovum into two p>ts4 ,ano!r
 groove !n cuts at "r angles to ?is     
subdivid+ ! two into f\r 7,figure #b74  
,ano!r groove1 at "r angles to bo? !    
=m]1 foll[s1 mak+ ! f\r eight 7,figure  
#c74 ,& s subdivision goes on4 ,! :ole  
process is call$ segm5tation or         
cleavage4   ,section #ae4 ,at ! end (   
segm5tation we get a holl[ sph]e ( small
 cells1 ! cells sep>at+ f "o ano!r      
c5trally & enclos+ a cavity z ! process 
proce$s4 ,?is is ! bla/osph]e1 %[n      
diagrammatically 9 ,figure #d1 & ( :i*  
an int]nal view1 r tru] to ! facts ( !  
case z reg>ds %ape1 is giv5 z ,figure   

#e4 ,! c5tral cavity is ! segm5tation   
cavity 7s4c474   ,section #af4          
,invag9ation foll[s 7,figure #f74 ,9 ?is
 process a portion ( ! bla/osph]e wall  
is ! tuck$ into ! re/1 z indicat$ by !  
arr[1 s t a two-lay]$ sack is =m$4 ,!   
space ar4 is ! ar*5t]on1 ! primordial   
inte/9e1 & its m\? is call$1 ! bla/opore
 7bp474 ,! out] lay] ( ?is d\ble-wall$  
sac is call$ ! epibla/4 ,= ! pres5t we w
 give ! inn] l9+ no special t]m4 ,! "y  
amphioxus has1 at ?is /age1 :i* is call$
 ! ga/rula /age1 a curi\s p>allelism )  
su* a l[ly =m z ! ,hydra ( our dit*es4  
,?is latt] creature1 l ! ga/rula1       
consi/s ess5tially ( two lay]s ( cells1 
an out] protective & s5sory lay]1 & an  
inn] dige/ive "o2 x has a primordial    
inte/9e1 or ar*5t]on1 & its m\? is      
sometimes reg>d$ z be+ a bla/opore4 ,all
 animals t h little yolk1 & />t e>ly 9  
life = !mselves1 pass ?r\gh a ga/rula   
/age1 sub/antially ! same z ?is (       
amphioxus4   ,section #ag4 ,! anus is   
p]=at$ lat] ne> ! region occupi$ at ?is 

/age by ! bla/opore4 ,h5ce ! ant]ior end
 ( ! future amphioxus1 ! head end1 is   
po9t+ t[>ds ! ,figure #f1 & ! lett]s ep4
 are m>k$ on ! side :i* w be dorsal4    
,section #ah4 ,figure #g i4 is a dorsal 
view ( ! ga/rula at a some:at lat] /age1
 & "h indications ( di/9ctly v]tebrate  
relation%ips already appe>4 ,figure #g  
ii4 is a cross-section1 its position1   
be+ %[n by cross-l9es 9 #g i4 & #f4     
,note fir/ t ! epibla/ along !          
mid-dorsal l9e is s9k+ 9 to =m :at is   
call$ ! neural plate 7n4p471 &          
simultane\sly on ei!r side ( x rise !   
neural folds 7n4f474 ,n[1 at ,figure #h1
 a slightly lat] /age is repres5t$1 & at
 #i i4 ! inturn$ "p is sep>at$ f ! g5]al
 ext]nal epibla/ z ! sp9al cord4 ,!     
rema9d] ( ! epibla/ con/itutes !        
epid]mis4   ,section #ai4 ,rev]t+ to    
,figure #g ii41 along ! dorsal side ( ! 
ar*5t]on a ?ick5+ ( its wall appe>s1 &  
is gradually p9*$ (f f x to =m a cellul>
 rod1 ly+ along "u ! n]v\s axis & above 
! inte/9e4 ,?is is ! noto*ord 7comp>e   

,figures #h & #i74   ,section #bj4      
,f9ally1 we note two s]ies ( buds (     
cells1 "o on ei!r side ( ! ar*5t]on 9   
,figure #g ii4 ,9 #h ^! buds h become   
holl[ vesicles1 gr[+ out f x1 ! coelomic
 p\*es4 ,!y are fur!r develop$ 9 #i2 & 9
 #i ii41 :i* is a diagrammatic figure1  
!y are indicat$ by dott$ l9es4 ,!y      
f9ally appe> to 78 entirely7 oblit]ate !
 segm5tation cavity-- !y c]ta9ly d s    
?r\gh\t ! body2 & _! cavities are 9 "t  
cut (f f ! mes5t]on1 by ! gradual       
con/riction ( _! op5+s4 ,9 ?is way !    
coelom 7body cavity7 arises z a s]ies ( 
holl[ ar*5t]ic outgr[?s1 & ms4 becomes !
 alim5t>y canal4 mt4c41 ! metapleural   
canals1 probably arise subsequ5tly to1 &
 indep5d5tly (1 ! g5]al coelomic space1 
by a splitt+ 9 ! body-wall sub/ance4    
,section #ba4 ,h5ce1 9 consid]+ !       
/ructure ( amphioxus1 we h ?ree s]ies ( 
cells f :i* its tissues are develop$3-- 
#a4 ,! epibla/4     #b4 ,walls ( !      
coelomic p\*es1 :i* =m 7a7 an inn] l9+  
to ! epibla/1 7b7 an out] coat+ to !    

hypobla/1 & 7c7 !    mes5t]y 7m471 by   
:i* ! inte/9e is support$4 ,?is is !    
mesobla/4     #c4 ,! l9+ ( ! mes5t]on1  
or hypobla/4  ,f ! epibla/ ! epid]mis 7n
 ! d]mis71 ! n]v\s sy/em 7includ+ !     
n]ves71 & ! s5sory "p ( all s5se organs 
are d]iv$4 ,f ! mesobla/ ! muscles1 !   
d]mis g5ital & excretory organs1        
circulatory fluid & app>atus1 any       
skeletal /ructures2 & all connective    
tissue are d]iv$4 ,! mass ( ! body is   
?us evid5tly made ( mesobla/4 ,!        
hypobla/ is ! l9+ ( ! inte/9e & ( ! gl&s
 :i* op5 into x2 & ! mat]ial ( !        
noto*ord is also reg>d$1 z hypobla/4    
,section #bb4 ,figure #i ii4 %[s all !  
ess5tial po9ts ( ! /ructure ( amphioxus4
 ,epibla/ is indicat$ by a l9e ( da%es1 
mesobla/ by dots1 & hypobla/1 d>k or    
black4 ,! true m\? is =m$ late by a     
tuck+-9 ( epibla/1 ! /omodaeum 7s4d471  
:i* meets & fuses ) ! hypobla/1 & is !n 
p]=at$4 ,! position ( ?is m\? is at !   
velum4 ,! =mation ( ! atrium has be5    
describ$4 ,! metapleural folds run =w>d 

9 front ( ! velum1 z ! epipleurs 7ep4 9 
,sections #a & #b71 & =m an oral hood   
7b4c471 ar\nd :i* ! t5tacles appe>1 &   
:i* is evid5tly n equival5t to !        
v]tebrate m\? cavity1 b 9 front ( &     
outside x4 ,! anus is =m$ by a tuck+ 91 
! proctodaeum1 simil> to ! /omodaeum4   
,section #bc4 ,! =mation ( ! respiratory
 slits is complicat$1 & difficult to    
describe1 b1 s9ce inve/igators h /ill to
 r5d] its mean+ app>5t1 x ne$ n deta9 ! 
elem5t>y /ud5t499  99 ,see ,balf\r's    
,embryology1 ,volume #b1 & ,qu>t]ly     
,j\rnal ( ,microscopical ,sci5ce ,m>*1  
#ahia4    ,que/ions on ,amphioxus  #a4  
,draw diagrams1 ) ! p>ts nam$1 ( !      
alim5t>y canal ( 7a7 amphioxus1 7b7 any 
craniate2 7c7 indicate v %ortly !       
pr9cipal /ructural diff]5ces betwe5 !   
two4  #b4 ,describe1 ) a diagram1 !     
circulation ( amphioxus4 ,comp>e x ) t (
 ! craniata4  #c4 ,draw f memory        
transv]se sections1 ( amphioxus 7a7 9 ! 
oral region1 7b7 ?r\gh ! ph>ynx1 7c7 j  
ant]ior1 & 7d7 j po/]ior to atrial pore4

  #d4 ,describe fully ! coelom (        
amphioxus1 & comp>e x ) t ( ! frog 9    
reg>d to 7a7 developm5t1 7b7 its        
relation to o!r organs 9 ! adult4  #e4  
,comp>e ! atrial cavity & coelom (      
amphioxus4 ,to :at s]ies ( cavities 9 ! 
frog are ! metapleural canals to be     
comp>$8  #f4 ,describe ! noto*ord (     
amphioxus1 & po9t out its diff]5ces f ! 
v]tebrate noto*ord4  #g4 ,describe1 )   
diagrams1 ! n]v\s sy/em ( amphioxus1 &  
comp>e its n]v\s axis1 9 detail1 ) t ( a
 v]tebrate4  #h4 ,comp>e ! g5ital organs
 ( amphioxus ) ^? ( a high] v]tebrate4  
#i4 ,:at /ructures h be5 reg>d$1 z r5al 
organs 9 amphioxus8  #aj4 ,:at is a     
ga/rula8 ,) :at l[] type has ! ga/rula  
be5 comp>$8 ,discuss ! comp>ison4       
-,developm5t  ,! ,developm5t ( ! ,frog  
,section #a4 ,we h n[ to consid] h[ !   
body ( ! frog is built up out ( ! egg   
cell1 b previ\sly to do+ s we mu/ rev]t 
to ! reproductive organs ( our type4    
,section #b4 ,9 ! te/es ( ! male is f\nd
 an intricate network ( tubuli1 ! l9+ ( 

:i* is1 ( c\rse1 an epi!lium4 ,! cells (
 ?is epi!lium h _! int]nal bord]s       
diff]5tiat$ into sp]matozoa1 :i*1 at a  
subsequ5t /age1 are lib]at$4 ,a         
sp]matozoon 7,figure #c1 ,%eet #ac1 sp47
 is a rod-%ap$ cell conta9+ a nucleus2 9
 fact1 consi/+ *iefly ( nucleus1 ) a    
tail1 ! flagellum1 :i* is vibratile1 &  
=ces ! sp]matozoon1 =w>d by its la%+4 ,!
 sp]matozoa float 9 a fluid :i* is !    
jo9t product ( ! te/es1 ant]ior "p ( !  
kidney1 & p]haps ! pro/ate gl&s4        
,section #c4 ,9 ! ov>y1 ! ova are =m$1 &
 gr[ to a consid]able size4 ,!y are     
nucleat$ cells1 ! nucleus go+ by !      
special "n ( ! g]m9al vesicle & !       
nucleolus ! g]m9al spot4 ,! ova prey ^u 
! adjac5t cells z !y develop4 ,!        
protoplasm ( ! ovum1 except at t "p ( ! 
surface :]e ! g]m9al vesicle lies1 is   
pack$ ) a great am\nt ( food mat]ial1 ! 
yolk granules4 ,?is yolk is non-liv+    
in]t matt]4 ,an ovum su* z ?is1 9 :i* ! 
protoplasm is conc5trat$ t[>ds "o pole1 
is call$ teloleci?al4   ,section #d4    

,aft] ! ovum has f9i%$ its gr[?1 &      
elaborat$ ! yolk )9 itself1 a peculi>   
*ange occurs 9 ! small area free f      
yolk-- ! animal pole1 9 :i* ! g]m9al    
vesicle lies4 ,?is g]m9al vesicle       
divides1 & "o moiety is budd$ (f f !    
ovum4 ,! ovum has1 9 fact1 und]gone cell
 division into a v l>ge cell conta9+ mo/
 ( its sub/ance1 & a small protoplasmic 
pimple surr\nd+ half ( its nucleus4 ,!  
disproportion is s great betwe5 ! two   
cells1 t ! ph5om5on does n at fir/      
sugge/ ! idea ( cell division1 & x is   
usually describ$ z ! extrusion ( ! fir/ 
pol> body4 ,!re foll[s a second & simil>
 small cell1 beh9d ! fir/1 ! second pol>
 body4 ,s9ce ! nucleus ( ! ovum has     
divid$ twice1 x is evid5t t ! nucleus   
rema9+ n[ 9 ! ovum is a qu>t] ( !       
orig9al nucleus4 ,v little protoplasm is
 giv5 (f ) ! pol> bodies2 !y play no    
fur!r "p 9 developm5t1 b simply drop (f 
& disappe>4 ,n only 9 ! frog's ovum1 b 9
 all v]tebrata1 two pol> bodies are giv5
 (f 9 ?is way be=e ! sexual process     

occurs4 ,_! exact mean+ has be5 widely  
discuss$4 ,x is fairly evid5t t "s      
mat]ial is remov$ f ! nucleus1 :i* w\ld 
be detrim5tal to fur!r developm5ts1 & ! 
po9t debat$ is :at is ! precise nature (
 ?is excret$ mat]ial4 ,?is burn+ "q we c
 sc>cely deal ) "h4   ,section #e4 ,b "h
 we may po9t out t 9 all cells !        
function ( ! nucleus appe>s to be to    
det]m9e gr[? & division4 ,x is ! c5tre (
 directive en]gy 9 ! cell4   ,section   
#f4 ,f]tilization is effect$ by a       
sp]matozoon meet+ ) ! ovum4 ,x fuses )  
x1 its nucleus becom+ ! male            
pro-nucleus4 ,?is & ! female            
pro-nucleus1 left aft] ! extrusion ( !  
pol> cells1 move t[>ds ea* o!r1 & unite 
to =m ! fir/ segm5tation nucleus4       
,section #g4 ,! ovum next beg9s to      
divide4 ,a furr[ cutt+ deep] & deep]    
divides x into two2 ano!r foll[s at "r  
angles to ?is1 mak+ ! two f\r1 & ano!r  
equatorial furr[ cuts (f ! animal pole f
 ! yolk or vegetative pole4 7,see ,%eet 
#bb1 ,figures #a1 #b1 & #c47 ,& s       

segm5tation 7 cleavage7 proce$s1 &1 at  
la/1 a holl[ sph]e1 ! bla/osph]e        
7,figure #d7 is =m$1 ) a segm5tation    
cavity 7s4c474 ,b1 because ( ! pres5ce (
 ! yolk at ! vegetative pole ( ovum1 & (
 ! me*anical resi/ance x (f]s to ! =ce (
 segm5tation1 ! protoplasm !re is n     
ne>ly s f9ely divid$-- ! cells1 t is to 
say1 are mu* l>g] ?an at ! animal pole4 
,! bla/osph]e ( ! frog is l :at !       
bla/osph]e ( amphioxus w\ld be1 if !    
future hypobla/ cells 7 enorm\sly l>g]  
?r\gh _! protoplasm be+ dilut$ ) yolk4  
,section #h4 ,! next phase ( developm5t 
has an equally curi\s resemblance to &  
diff]5ce f :at occurs 9 ! case ( ! ova (
 animals :i* d n conta9 yolk4 ,9 su*    
types 7e4g41 amphioxus7 a "p ( !        
bla/osph]e wall is tuck$ into ! re/1 & a
 ga/rula =m$ by ?is process (           
invag9ation4 ,9 ! frog 7,figure #e7 !re 
is a tuck+-91 b ! "p t %\ld lie )9 !    
ga/rula1 ! yolk-conta9+ cells1 are f>   
l>g] ?an ! epibla/ 7ep47 :i* %\ld1 =m ! 
out] lay] ( cells4 ,h5ce ! epibla/ c    

only by cont9ual gr[? accommodate :at x 
mu/ embrace1 & ! process ( tuck+-9 is   
accompani$ by "o ( gr[? ( ! epibla/1 z  
%[n by ! unb>b$ arr[1 ov] ! yolk4 ,?is  
/age is call$ ! ga/rula /age2 ar4 is !  
cavity ( ! ga/rula1 ! ar*5t]on2 b4p4 is 
its op5+ or bla/opore4 ,su* a ga/rula1  
=m$ ma9ly by ov]gr[? ( ! epibla/1 is    
call$ an epibolic ga/rula1 z di/+ui%$ f 
! invag9ate ga/rula ( amphioxus4 ,!     
diff]5ce is evid5tly entirely due to !  
pres5ce ( yolk1 & ! consequ5t           
modification ( invag9ation 9 ! =m] case4
   ,section #i4 ,comp>+ ! two ga/rulas1 
x is n difficult to see t if we imag9e !
 v5tral wall ( ! ar*5t]on ( amphioxus to
 h its cells enorm\sly enl>g$ ?r\gh !   
mix+ ( yolk ) _! protoplasm1 we %\ld h a
 ga/rula ess5tially l t ( ! frog4       
,section #aj4 ,figure #f %[s a slightly 
lat] ovum ?an ,figure #e1 se5 f ! dorsal
 side4 b4p4 is ! bla/opore4 ,9 front ( t
 appe>s a groove1 ! neural groove1      
bord]$ on ei!r side by a ridge1 ! neural
 fold 7n4f474 ,?is is se5 9 section 9   

,figure #g2 s4c4 is ! neural groove2    
n4f41 z be=e1 ! neural fold4 ,! neural  
folds ultimately b5d ov] & meet above1 s
 t s4c4 becomes a canal1 & is f9ally    
sep>at$ f ! epibla/ to =m ! sp9al cord4 
,bel[ ! neural groove a ?ick5+ ( !      
dorsal wall ( ! ar*5t]on appe>s1 & is   
p9*$ (f to =m a longitud9al rod1 !      
precursor ( ! v]tebral column1 !        
noto*ord1 %[n 9 ,figure #g 7n4c471 z    
imp]fectly p9*$ (f4   ,section #aa4     
,simultane\sly1 on ei!r side ( !        
noto*ord appe> a s]ies ( solid masses ( 
cells1 d]iv$ ma9ly by cell division f ! 
cells ( ! wall ( ! ar*5t]on1 & fill+ up 
& oblit]at+ ! segm5tation cavity4 ,^!   
masses increase 9 numb] by ! addition ( 
fre% ones beh9d1 dur+ developm5t1 & are 
visible 9 ! dorsal view z brick-l       
masses1 ! mesobla/ic somites or         
proto-v]tebrae 7,figure #f1 i41 ii41    
iii474 ,9 ,figure #g1 ^! masses are     
indicat$ by dott+4 ,9 su* a primitive   
type z amphioxus ^! mesobla/ic -somites-
 masses conta9 a cavity1 de/9$ to be !  

future body cavity1 f ! fir/4 ,9 ! frog1
 ! cavity is n at fir/ app>5t2 !        
mesobla/ at fir/ seems q solid1 b       
subsequ5tly :at is call$ ! splitt+ ( !  
mesobla/ occurs1 & ! body cavity 7b4c4 9
 ,figure #g7 appe>s4 ,! out] mesobla/1  
ly+ imm$iately "u ! epibla/1 con/itutes 
! sub/ance ( ! somatopleur1 & f x w be  
=m$ ! d]mis1 ! muscles ( ! body wall1   
almo/ all ! c>tilage & bone ( !         
skeleton1 ! sub/ance ( ! limbs1 !       
kidneys1 g5ital organs1 he>t &          
bloodvessels1 &1 9 %ort1 ev]y?+ betwe5 !
 d]mis & ! coelom1 except ! n]v\s sy/em 
& n]ves1 & ! noto*ord4 ,! inn] mesobla/1
 ! mass ( ! splan*nopleur1 w =m ! muscle
 & connective tissue ( ! wall ( !       
alim5t>y canal1 & ! b9d+ sub/ance ( !   
liv] & o!r gl&s t op5 into ! canal4     
,section #ab4 ,figure #h is "o :i* we   
reproduce1 ) ! necess>y *anges 9 ea*    
plate ( embryological figures giv5 9 ?is
 book1 s t ! /ud5t w f9d x a conv5i5t1  
"o = ! purpose ( comp>ison4 ,! l9es (   
da%es1 9 all cases1 signify -epibla/-   

hypobla/ 1 ! unbrok5 black l9e is       
-hypobla/-1 epibla/ dott+ %[s mesobla/1 
& ! %ad$ rod 7n4c47 is ! noto*ord4 c4s4 
is ! sp9al cord2 br4#a1 br4#b1 br4#c are
 ! ?ree prim>y vesicles :i* con/itute ! 
bra91 & :i* =m =e1 mid1 & h9d bra9      
respectively4 ,i4 is ! inte/9e & ,y4 !  
yolk cells t at ?is e>ly /age con/itute 
its v5tral wall4   ,section #ac4 ,figure
 #i gives a simil> diagram ( a lat]     
/age1 b "h ! bla/opore is clos$4 ,an    
epibla/ic tuck+-9 at /41 ! /omodaeum    
pre-figures ! m\?2 pr41 ! proctodaeum1  
is a simil> po/]ior invag9ation :i* w   
become ! anus4 ,y41 ! yolk1 is evid5tly 
mu* absorb$4 ,figure #aj is a "y        
tadpole1 se5 f ! side4 ,! /ill unabsorb$
 yolk 9 ! v5tral wall ( ! mes5t]y gives 
! creature a big belly4 ,its m\? is     
suctorial at ?is /age1 & beh9d x is a   
suck] 7s47 by :i* ! l>vae atta* !mselves
 to float+ re$s & wood1 z %[n 9 ! ?ree  
black figures bel[4   ,section #ad4 ,we 
may n[ consid] ! developm5t ( ! diff]5t 
organs slightly m 9 detail1 ?\gh mu* (  

?is has already be5 approa*$4 ,! n]v\s  
sy/em1 be=e ! closure ( ! neural groove1
 has ?ree ant]ior dilatations1 ! =e-1   
mid-1 & h9d-bra9s1 ! fir/ ( :i* gives   
rise by holl[ outgr[?s to two pairs (   
lat]al /ructures1 ! hemisph]es & ! optic
 vesicles4 ,! latt] give rise to ! ret9a
 & optic n]ve z describ$ 9 ,developm5t  
,section #dj4   ,section #ae4 ,!        
hypobla/ic noto*ord is e>ly embrac$ by a
 mesobla/ic %ea? d]iv$ f !              
protov]tebrae4 ,?is becomes truly       
c>tilag9\s1 & at regul> int]vals is     
alt]nately ?ick] & ?9n]1 compress+ !    
noto*ord at ! ?ick] p>ts4 ,h5ce !       
noto*ord has a bead$ =m )9 ?is1 at fir/1
 cont9u\s c>tilag9\s %ea?4 ,?is %ea? is 
soon cut into a s]ies ( v]tebral bodies 
by jo9t+s appe>+ ?r\gh ! po9ts :]e !    
c>tilage is ?icke/ & ! noto*ord mo/     
con/rict$4 ,h5ce :at rema9s ( ! noto*ord
 lies )9 ! v]tebral bodies 9 ! frog2    
:ile 9 a c>tilag9\s fi%1 su* z !        
dog-fi%1 or 9 ! embryonic rabbit1 ! l9es
 ( sep>ation appe> :]e ! noto*ord is    

?icke/1 & x comes to lie betwe5         
holl[-fac$ v]tebrae4 ,c>tilag9\s neural 
ar*es & sp9es1 =m$ outside ! noto*ordal 
%ea?1 enclose ! sp9al cord 9 an arcade4 
,! f9al phase is ossification4 ,z !     
tadpole approa*es ! frog /age ! v]tebral
 column 9 ! tail is rapidly absorb$1 &  
its ve/iges appe> 9 ! adult z ! uro/yle4
   ,section #af4 ,! developm5t ( ! skull
 is entirely dissimil> to t ( ! v]tebral
 column4 ,x is %[n on ,figures #a & #h1 
,%eet #ad2 & 9 ! section devot$ to !    
frog's skull a v complete acc\nt ( !    
process is giv54 ,! process (           
ossification is describ$ "u ! hi/ology (
 ! ,rabbit4   ,section #ag4 ,! orig9 ( !
 circulatory & respiratory organs is (  
especial int]e/ 9 ! frog4 ,9 ! tadpole  
we h ess5tially ! necessities &         
organization ( ! fi%2 9 ! adult frog we 
h a cle> exposition ( ! /ructure (      
pigeon & rabbit4 ,! tadpole has1 at     
fir/1 a /raight tubul> he>t1 burr[$ out 
9 somatic mesobla/1 & produc$ =w>d into 
a truncus art]iosus4 ,f ?is arise f\r   

aff]5t bran*ial art]ies1 runn+ up along 
! sides ( ! f\r bran*ial ar*es1 &       
supply+ gills4 ,!y unite above on ei!r  
side 9 pair$ hyp]-bran*ial art]ies1 :i* 
meet beh9d dorsal to ! liv]1 to =m a    
m$ian dorsal aorta4 ,int]nal & ext]nal  
c>otid art]ies supply ! head4 ,^! f\r   
aff]5t bran*ial ar*es are equival5t to !
 fir/ f\r ( ! five vessels ( ! dog-fi%4 
,at fir/1 ! pair$ gills are ?ree 9      
numb]1 ext]nal1 & tree-l1 cov]$ by      
epibla/ 7,figures #aj & #aa1 e4g471 & n 
to be comp>$ to fi% gills 9 /ructure1 or
 9 fact -)- to any o!r gills )9 ! limits
 ( ! v]tebrata4 ,subsequ5tly            
7hypobla/ic7 int]nal gills 7int4g41     
,figure #ab71 /rictly homolog\s ) !     
gills ( a fi%1 appe>4 ,!n a flap ( sk9  
outside ! hyoid ar* gr[s back to cov]   
ov] ! gills2 ?is is ! op]culum 7op4 9   
,figures #aa & #ab1 ,%eet #bb71 & x     
f9ally encloses !m 9 a gill *amb]1 op5  
only by a pore on ! left1 :i* resembles 
9 /ructure & physiological mean+1 b     
diff]s evid5tly v widely 9 developm5t1 f

 ! amphioxus atrium4 ,at ?is "t1 ! lungs
 are develop+ z pair$ holl[ outgr[?s on 
! v5tral side ( ! ?roat 7,figure #ab1   
,l474 ,z ! limbs develop1 & ! tail      
dw9dles1 ! gill *amb] is oblit]at$4 ,!  
capill>y int]ruptions ( ! gills on !    
bran*ial ar*es 7aortic ar*es7 are also  
oblit]at$4 ,! c>otid gl& occupies !     
position ( ! fir/ ( ^! 9 ! adult4 ,!    
front bran*ial ar* "h1 z 9 all high]    
v]tebrata1 becomes ! c>otid ar*2 ! l+ual
 repres5ts ! base ( a pre-bran*ial      
vessel2 ! second bran*ial becomes !     
aortic ar*4 ,! f\r? loses its connection
 ) ! dorsal aorta1 & s5ds a bran* to !  
develop+ lung1 :i* becomes ! pulmon>y   
art]y4 ,! ?ird disappe>s4 ,a some:at    
diff]5t acc\nt to ?is is /ill f\nd 9 "s 
text-books ( ! fate ( ?is ?ird bran*ial 
ar*4 ,balf\r w\ld appe> to h be5 (      
op9ion t x gave rise to ! cutane\s      
art]y1 & t ! ?ird & f\r? vessels        
coalesc$ to =m ! pulmocutane\s1 ! f\r?  
ar* mov+ =w>d s z to arise f ! base ( ! 
?ird2 & mo/ elem5t>y works foll[ him4   

,?is op9ion 0 /r5g!n$ by ! fact t 9 !   
high] types 7reptiles1 birds1 & mammals7
 no f\r? bran*ial ar* 0 obs]v$1 & !     
app>5t ?ird1 becomes ! pulmon>y4 ,b x   
has s9ce be5 %[n t a transitory ?ird ar*
 appe>s & disappe>s 9 ^! types4         
,section #ah4 ,! orig9 ( ! r5al organ & 
duct has v consid]able controv]sial     
int]e/499 ,9 ,figure #ac1 ,%eet #bb1 a  
diagrammatic cross-section1 ( an embryo 
is %[n4 ,i4 is ! inte/9e1 coe4 ! coelom1
 s4c4 ! sp9al cord2 n4c4 ! noto*ord1    
surr\nd$ by n4s41 ! noto*ordal %ea?1 ao4
 is ! dorsal aorta4 ,9 ! masses (       
somatic mesobla/ on ei!r side1 a        
longitud9al canal appe>s1 :i*1 9 !      
torp$o1 a fi% relat$ to ! dog-fi%1 & 9 !
 rabbit1 & possibly 9 all o!r cases1 is 
epibla/ic 9 orig94 ,?is is ! segm5tal   
duct1 :i* p]si/s1 app>5tly1 z !         
,wolffian duct 7,w4,d474 ,v5tral to ?is 
appe>s a p>allel canal1 ! ,mull]ian duct
 7,m4,d471 :i* is (t5 describ$ z be+    
split (f f ! segm5tal duct1 b :i* is1 v 
probably1 an indep5d5t /ructure 9 !     

frog4 ,a numb] ( tubuli1 at fir/        
metam]ically arrang$1 n[ appe>1 ea*     
op5+1 on ! "o h&1 into ! coelom by a    
ciliat$ m\?1 ! nephro/ome 7n4s471 & on !
 o!r into ! segm5tal duct4 ,^! tubuli   
are ! segm5tal tubes or nephridia4 ,!re 
gr[s out f ! aorta1 t[>ds ea*1 a bun*1 (
 bloodvessels1 ! glom]ulus 7comp>e      
,section #fb1 ,rabbit74 ,^! tubuli      
ultimately become1 9 "p1 ! r5al tubuli1 
s t ! primitive kidney /ret*es1 at fir/1
 along ! l5g? ( ! body cavity f !       
region1 ( ! gill-slits backw>d4 ,!      
ant]ior "p ( ! kidney1 call$ !          
pronephros1 disappe>s 9 ! lat] l>val    
/ages4 ,int]nal to ! kidney on ei!r side
 !re has appe>$ a longitud9al ridge1 !  
g5ital ridge 7g4r471 :i* gives rise to  
te/es or ov>y1 z ! case may be4  99 ,9 !
 discussion :e!r ! v]tebrata h aris5 f  
"s ance/ral type1 l ! e>?worm1          
metam]ically segm5t$1 & ( fairly high   
organization1 or f a mu* l[] =m1        
possibly ev5 f a coel5t]ate4 ,su* a     
discussion is entirely outside ! scope (

 ! book1 ?\gh its m5tion is necess>y to 
expla9 ! importance giv5 to ^! organs4  
,section #ai4 ,! /ud5t %\ld n[ comp>e ! 
figures on ,%eet #ag4 ,9 ! male1 tubul> 
connections are e/abli%$ betwe5 ! te/es 
& ! middle "p ( ! primitive kidney      
7mesonephros74 ,^! connections are !    
vasa eff]5tia 7v4e471 & ! mesonephros is
 n[ equival5t to ! epididymis ( !       
rabbit4 ,! ,wolffian duct is ! urog5ital
 duct ( ! adult1 & ! ,mull]ian duct is  
entirely absorb$1 or rema9s1 m or less1 
9 exceptional cases4  ,9 ! female1 !    
,mull]ian duct increases greatly 9      
l5g?-- s t at sexual maturity its :ite  
coils appe> ?ick] & long] ?an !         
inte/9e-- & becomes ! oviduct2 !        
,wolffian duct is ! uret]1 & !          
mesonephros is n p]v]t$ 9 function f its
 prim>y r5al duty4   ,section #bj4      
,tabulat+ ^! facts--     ,9 ! adult     
male3       ,pronephros disappe>s4      
,! ,mull]ian duct 78  pronephric duct7  
disappe>s4       ,mesonephros           
,epididymis2 its duct1 ! urog5ital4     

,metanephros & duct1 n cle>ly m>k$ (f f 
,mesonephros4       7,comp>e ,dog-fi%1  
,section #ai47     ,9 ! adult female3   
,pronephros disappe>s4       ,!         
,mull]ian duct1 ! oviduct4              
,mesonephros & ,metanephros1 ! kidney1 &
 _! unsep>at$          ducts1 ! uret]s4 
,section #ba4 ,h]maphrodism 7i4e41 cases
 ( common sex7 is occasionally f\nd     
among frogs2 ! te/is produces ova 9     
places1 & ! ,mull]ian duct is reta9$ &  
functional4 ,! ciliat$ nephro/omata     
rema9 op5 to a late /age ( developm5t 9 
! frog1 & 9 _m amphibia ?r\gh\t life4   
,_! connection ) ! r5al tubuli is1      
h[ev]1 lo/4   ,section #bb4 ,! alim5t>y 
canal is1 at fir/1 a /raight tube4 ,its 
disproportionate increase 9 l5g? ?r[s x 
into a spiral 9 ! tadpole 7int4 ,figure 
#aa71 & acc\nts = its coil+ 9 ! frog4 ,!
 liv] & o!r dige/ive gl&s are fir/ =m$1 
l ! lungs1 z holl[ outgr[?s1 & _! l9+ is
 !re=e hypobla/ic4 ,! greate/ relative  
l5g? ( inte/9e is f\nd 9 ! tadpole1 :i*1
 be+ a purely vegetable fe$]1 mu/ ne$s  

effect ! maximum am\nt ( prep>atory     
*ange 9 its food4    ,! ,developm5t ( ! 
,f[l  ,section #bc4 ,! frog has an ovum 
) a mod]ate all[ance ( yolk1 b !        
quantity is only suffici5t to />t !     
little animal a "p ( its way t[>ds !    
adult /ate4 ,! f[l1 on ! contr>y1 has an
 enorm\s ovum1 gorg$ excessively1 )     
yolk1 & z a consequ5ce ! *ick is almo/  
p]fect$ :5 x is hat*$4 ,! s-call$ yolk1 
! yell[ ( an egg1 is ! ovum prop]2 ar\nd
 t is a coat+ ( :ite album51 9 a %ell   
membrane & a %ell4 ,at ei!r end ( ! yolk
 7,figure #a1 y47 twi/$ /r&s ( album9\s 
matt]1 ! *alazae 7*47 keep ! yolk 9     
place4 ,! animal pole is a small grey   
protoplasmic area1 ! g]m9al area 7g4a471
 on ! yolk4   ,section #bd4 ,we po9t$   
out t ! pres5ce ( ! yolk 9 ! frog's egg 
l$ to a diff]5ce 9 ! size ( ! cells at !
 animal & vegetable poles4 ,! late      
,f4,m4 ,balf\r1 borr[+ a ma!matical     
te*nicality1 sugge/$ t ! rate (         
segm5tation 9 any "p ( an ovum v>ies    
inv]sely ) ! am\nt ( yolk4 ,9 ! f[l's   

egg1 except j at ! g]m9al area1 ! active
 protoplasm is at a m9imum1 ! in]t yolk 
at a maximum2 ! ratio ( yolk to         
protoplasm is practically inf9ity1 & !  
yolk !re=e does n segm5t at all4 ,! yolk
 has dilut$ ! active protoplasm s mu* z 
to r5d] its influ5ce inappreciable4 ,!  
g]m9al area segm5ts1 & lies ^u ! yolk   
:i* has defeat$ ! ef=ts ( its small m+l+
 ( protoplasm to divide4 ,su* a type (  
segm5tation 9 :i* only "p ( ! ovum      
segm5ts is call$ m]obla/ic4 ,if we      
comp>e ?is ) ! typical bla/osph]e ( !   
l[] type1 we see t x is1 z x 71 flatt5$ 
out on ! yolk4 ,?is /age is %[n 9       
section 9 ! l[] figure ( ,figure #a4    
b4d41 ! bla/od]m1 is f ?is po9t ( view1 
a "p ( ! ripp$ & flatt5$ bla/osph]e1    
spread out on ! yolk2 s4c4 is !         
segm5tation cavity1 & y4 ! yolk4        
,section #be4 ,!re is no op5 invag9ation
 ( an ar*5t]on 9 ! f[l1 z 9 ! frog--1 ! 
ga/rula1 l ! bla/osph]e1 /age is also   
mask$4 ,b1 9 ! h9d] region ( ! g]m9al   
area1 a ?ick mass ( cells1 gr[s inw>d & 

=w>d1 &1 appe>+ 9 ! dorsal view ( ! egg 
z a :ite /reak1 is call$ ! primitive    
/reak 7p4s474 ,by a comp>ison ( !       
figures ( frog & f[l ! /ud5t w easily   
p]ceive ! complete correspond5ce ( !    
position ( ?is ) ! bla/opore ( ! frog4  
,! relation ( ! two w be easily und]/ood
 if we comp>e ! f[l's ar*5t]on to a     
glove-f+] "u pressure-- its cavity is   
oblit]at$-- & ! frog's to ! glove-f+]   
bl[n out4 ,! t5sion ( ! protoplasm1     
/ra9+ ov] ! enorm\s yolk1 answ]s to !   
pressure4 ,! ga/rula 9 ! f[l is solid4  
,! primitive /reak is1 9 fact1 ! sc> ( a
 clos$ bla/opore4 ,z we %\ld expect f   
?is view ( its homology1 at ! primitive 
/reak1 ! ?ree embryonic lay]s are       
cont9u\s & indi/+ui%able 7,figure #b74  
,else:]e 9 ! bla/od]m !y are di/9ctly   
sep>ate4 ,j z ! yolk cells ( ! frog =m !
 v5tral wall ( ! inte/9e1 s nuclei appe>
 along ! upp] side ( ! yolk ( ! f[l1 :]e
 "s protoplasm /ill exi/s1 & give rise  
to ! v5tral hypobla/ic cells4 ,by       
conceiv+ a gradually increas+ am\nt (   

yolk 9 ! hypobla/ic cells 9 ! v5tral    
side ( ! ar*5t]on1 ! sub/antial id5tity 
( ! ga/rula /age 9 ! ?ree types1 :i* at 
fir/ appe> s /rik+ly diff]5t1 w be      
p]ceiv$4 ,c>ry ,figures #d & #e ( ! frog
 "o /ep fur!r by increas+ ! size ( !    
%ad$ yolk & leav+ x unsegm5t$1 & in/ead 
( ar4 9 #e %[ a solid mass ( cells1 & ! 
condition ( ?+s 9 ! f[l w\ld at once be 
r5d]$4   ,section #bf4 ,figure #c;a ( ! 
f[l w conv5i5tly s]ve = comp>ison )     
,figure #g ( ! frog4 ,! inturn+ ( !     
m$ull>y groove is entirely simil> 9 !   
two cases4 ,! mesobla/ appe>s z solid   
mesobla/ic somites4 ,9 ! section above  
,figure #d ?is lay] is %[n z hav+ split 
into somatopleur 7s47 & splan*nopleur   
7sp*474 ,figure #c answ]s to ,figure #f 
( ! frog1 & ,figure #d is a lat] /age1 9
 :i* ! m$ull>y groove is beg9n+ to close
 at its middle "p4 ,! cle> club-%ap$    
area ar\nd ! embryo 7a4p47 is ! area    
pellucida2 ! l>g] area )\t ?is is ! area
 opaca 7a4o471 9 :i* ! fir/ bloodvessels
 arise by a runn+ toge!r & a            

specialization ( cells4 ,! entire g]m9al
 area gr[s /eadily at its edges to creep
 ov] & enclose ! yolk4   ,section #bg4  
,s f>1 ! ess5tial diff]5ces betwe5 !    
developm5t ( f[l & frog1 ! m]obla/ic    
segm5tation1 abs5ce ( a typical ga/rula1
 & ! primitive /reak1 seem compreh5sible
 on ! !ory t su* diff]5ces are due to ! 
pres5ce ( an enorm\s am\nt ( yolk4      
,ano!r diff]5ce t appe>s lat] is t1 :ile
 ! tadpole has an effici5t pronephros1 !
 f[l1 :i* has no l>val 7free imp]fect7  
/ages 9 its life hi/ory1 has ! m]e/     
indication ( su* a /ructure4   ,section 
#bh4 ,ano!r /rik+ contra/1 due to1 or   
connect$ )1 ?is ple?ora ( yolk1 is !    
diff]5tiation ( a yolk sac 7 umbilical  
vesicle7 & ! developm5t ( two new       
/ructures1 ! amnion & allantois1 9 !    
f[l4 ,if ! /ud5t w comp>e ,figure #aj ( 
! frog1 he w see t ! develop+ tadpole   
encloses 9 its abdom5 all ! yolk provid$
 = x4 ,?is is a physical impossibility 9
 ! f[l4 ,9 ! f[l 7,figure #b1 ,%eet #bd7
 ! enorm\s yolk 7,y47 lies outside ( !  

embryo1 &1 z ! cells ( ! g]m9al area gr[
 sl[ly ov] x1 umbilical bloodvessels are
 develop$ to absorb & c>ry ! mat]ial to 
! embryo4 ,9 ! case ( an embryo s9k+ 9  
^u1 z x absorbs1 ?is mass ( nutritive   
mat]ial1 a necessity = "s respiratory   
/ructure is evid5t4 ,f ! h9d] end ( !   
f[l's inte/9e1 9 a position correspond+ 
to ! s-call$1 ur9>y bladd] ( ! frog1 a  
solid outgr[?1 ! allantois1 :i* spe$ily 
becomes holl[1 appe>s4 ,e>ly /ages are  
%[n 9 ,figures #a & #b1 ,%eet #bd 7al472
 :ile ! same ?+ is %[n m                
diagrammatically on ,%eet #bc1 ,figure  
#f 7all474 ,?is becomes at la/ a great  
holl[ sac1 :i* is appli$ closely to !   
por\s %ell1 & ! ext5t ( :i* w be        
appreciat$ by look+ at ,figure #e1 ,%eet
 #bd1 :]e ! allantois is %ad$4          
,allantoic bloodvessels ramify ?ickly   
ov] its walls1 & a]ation occurs ?r\gh ! 
p]meable %ell4   ,section #bi4 ,! nature
 ( ! amnion w be und]/ood by foll[+     
,figures #d;b1 #e1 & #f on ,%eet #bc4 ,!
 ?ree embryonic lay]s are indicat$ by   

brok5 l9es1 dots1 & black l9es1 j z !y  
are 9 ! frog diagrams4 ,n only is !     
embryo sl[ly p9*$ (f f ! yolk sac       
7y4s471 b1 z ! yolk is absorb$ b5ea? x1 
& x gr[s 9 size1 x s9ks into ! space ?us
 made1 ! extra-embryonic somatopleur &  
epibla/ rise up r\nd x z two folds1 :i* 
are se5 clos+ 9 #e1 & clos$ 9 #f1 ov] ! 
dorsal side ( ! "y *ick4 ,9 ?is way a   
cavity1 a41 l9$ by epibla/1 & call$ !   
amniotic cavity1 is =m$4 ,dorsal to ?is1
 9 #f1 comes a space l9$ by somatic     
mesobla/1 & cont9u\s ) p4p41 !          
pleuro-p]itoneal cavity1 or body cavity 
( ! embryo4 ,outside ?is1 aga91 is a    
lay]1 ( somatopleur int]nally & epibla/ 
ext]nally1 ! false amnion 7f4a471 :i* is
 cont9u\s ) ! s]\s membrane 7s4m47      
enclos+ ! re/ ( ! egg4 ,! /ud5t %\ld1   
c>efully copy ^! diagrams1 ) col\r$     
p5cils or inks = ! diff]5t lay]s1 & %\ld
 comp>e !m ) ! m reali/ic r5d]+s (      
,figures #b1 #e1 & #h1 ,%eet #bd4       
,section #cj4 ,! he>t 9 ! f[l appe>s    
fir/ z a pair ( vessels1 :i* unite to =m

 a /raight trunk 9 ! m$ian l9e1 z !     
flatt5$-out embryo closes 9 f ! yolk4 ,!
 way 9 :i* ?is /raight trunk is ?r[n1   
fir/ ( all1 into ! ,s %ape ( ! fi% he>t1
 & !n gradually assumes ! adult =m1 is  
indicat$ r\ghly by ,figure #c4 ,9 "o    
respect ! developm5t ( ! he>t does n    
foll[ ! l9es "o w\ld expect4 ,s9ce1     
betwe5 ! fi% & ! high] =m comes !       
condition ( su* an animal z ! frog1 9   
:i* ! auricles are divid$1 :ile !re is  
only "o v5tricle1 we might expect a /age
 9 :i* ! develop+ *ick's he>t w\ld h "o 
v5tricle1 & a septum betwe5 ! auricles4 
,b1 z a matt] ( fact1 ! v5tricles 9 f[l 
& rabbit are sep>at$ fir/1 & ! sep>ation
 ( ! auricles foll[s1 & is b>ely        
complete at bir?4   ,section #ca4 ,two  
vitell9e ve9s f ! yolk sac 7v4v47 fl[   
into ! he>t f beh9d1 z %[n 9 ,figure #a4
 ,a lat] m complete & m diagrammatic    
figure ( ! circulation is se5 9 ,figure 
#g4 ,at fir/ !re are two ant]ior c>d9al 
7a4c471 & two po/]ior c>d9al ve9s 7p4c47
 unit+ to =m ,cuvi]ian s9uses 7c4s47 t  

op5 into ! he>t j z 9 ! dog-fi%4 ,b lat]
 ! inf]ior cava is develop$ & ext5ds    
backw>d1 ! po/]ior c>d9als atrophy1 !   
,cuvi]ian s9uses become ! sup]ior cavae1
 & ! ant]ior c>d9als ! int]nal jugul>   
ve9s4 ,! vitell9e ve9s 7v4v47 fl[1 at   
fir/1 un9t]rupt$ly ?r\gh ! liv] to !    
inf]ior cava1 b1 z developm5t proce$s1 a
 capill>y sy/em is e/abli%$ 9 ! liv]1 & 
! ?r\gh communication1 ! ductus v5osus1 
is r$uc$-- at la/-- completely4 ,be>+ 9 
m9d t ! yolk is outside ! body 9 ! f[l &
 inside x 9 ! frog1 ! vitell9e ve9s ( ! 
=m] h a consid]able resemblance 9       
position1 & 9 _! relation to ! portal   
ve91 to a portion ( ! s+le ant]ior      
abdom9al ve94 ,blood is tak5 out to !   
allantois1 h[ev]1 by ! art]ies ( ! latt]
 type4   ,section #cb4 ,five aortic     
ar*es are g5]ally /at$ to appe> altoge!r
 9 ! f[l1 b n simultane\sly4 ,! fir/    
two1 ! m&ibul> & ! hyoid vascul> ar*es1 
e>ly disappe>1 & are n comp>able to any 
9 ! frog4 ,! ?ird is ! fir/ bran*ial    
ar*1 &1 l ! correspond+ ar* 9 ! frog1   

=ms ! c>otid art]y2 ! second bran*ial is
 ! aortic ar*2 & :at has hi!rto be5     
reg>d$ z ! ?ird 7! fif? ar*1 i4e47 !    
pulmon>y art]y4 ,a transitory ar*1 x is 
n[ kn[n1 h[ev]1 appe>s betwe5 ! second  
bran*ial & ! la/1 & x is !re=e ! f\r?   
bran*ial ar* :i* is ! pulmon>y1 j z x is
 9 ! frog4   ,section #cc4 ,blood1 x may
 be m5tion$1 fir/ appe>s 9 ! area       
vasculosa1 ! out] portion ( ! area      
opaca4 ,embryonic cells s5d out         
processes1 & s become multipol>2 !      
processes ( adjac5t cells coalesce4 ,!  
nucleus divides1 & empty spaces appe> 9 
! sub/ance ( ea* ( ! cells4  ,9 ?is way1
 ! cavities ( ! small] vessels &        
capill>ies are =m$1 & ! products ( !    
int]nal divisions ( ! cells become !    
corpuscles )9 ! vessels4 ,! r$ blood    
corpuscles ( ! rabbit1 x may be add$1   
are nucleat$ = a consid]able portion (  
embryonic life4 ,l>g] vessels & ! he>t  
are burr[$1 z x 71 out ( masses (       
mesobla/ cells4 ,! c\rse ( ! blood 9 !  
embryo is by ! ve9s to ! "r auricle1    

!nce ?r\gh ! imp]fection ( ! auricul>   
septum already allud$ to1 into ! left   
auricle4 ,!n ! left v5tricle1 aortic    
ar*es 7= ! future pulmon>y art]y is 9   
communication by a "p pres5tly block$1 !
 ductus art]i\s1 ) ! sy/emic aorta71    
art]ies1 capill>ies1 ve9s4 ,! liv]      
capill>y sy/em & ! pulmon>y sy/em only  
become ins]t$ ^u ! circulation at a     
comp>atively late /age4   ,section #cd4 
,) ! exception ( ! r$uction ( !         
pronephros1 :at has be5 said ( !        
developm5t ( ! frog's n]v\s sy/em1 r5al 
& reproductive organs1 & skeleton1      
applies suffici5tly to ! f[l = our      
pres5t purposes4 ,! entire sep>ation (  
,wolffian & ,mull]ian ducts f ! v beg9n+
 ( developm5t is "h beyond all "q 7vide 
,section #ah74 ,b ! noto*ord 9 ! f[l is 
n s di/9ctly connect$ ) ! hypobla/1 & s 
di/9ct f ! mesobla/1 z x is 9 ! l[]     
type1 & no gills1 int]nal or ext]nal1   
are ev] develop$4 ,! gill slits occur ) 
a modification due to ! slitt+ & flatt5+
 out ( ! embryo1 already insi/$ ^u2 =1  

:]eas 9 ! tadpole !y may be describ$ z  
p]=ations1 9 ! f[l !y appe> z f\r not*es
 betwe5 +r[+ processes t are endeav\r+  
to meet 9 ! middle l9e4    ,!           
,developm5t ( ! ,rabbit  ,section #ce4  
,! e>ly developm5t ( ! rabbit is apt to 
puzzle /ud5ts a little at fir/4 ,we h an
 ovum practically free f yolk           
7aleci?al71 &1 !re=e1 we f9d x divid+   
completely & almo/ equally4 ,we         
naturally assume1 f :at we h le>nt1 t ! 
next /ages w be ! =mation ( a holl[     
bla/osph]e1 invag9ation1 a ga/rula =m+  
mesobla/ by holl[ outgr[?s f ! ar*5t]on1
 & s on4 ,!re is no yolk "h to sub/itute
 epiboly 7,section #i7 = invag9ation1   
nor to oblit]ate ! ar*5t]on & !         
bla/opore ?r\gh its pressure4  ,yet none
 ( ^! ?+s we h anticipat$ occur6  ,we   
f9d solid mesobla/ic somites1 we f9d    
primitive /reak1 allantois & amnion1    
features we h j be5 expla9+ z !         
consequ5ce ( an excess ( yolk 9 ! egg4  
,we ev5 f9d a yolk sac ) no yolk 9 x4   
,section #cf4 ,a solid mass ( cells is  

=m$ at ! beg9n+1 call$ a morula1 ,figure
 #a4 ,9 ?is we are able to di/+ui% r    
small] out] lay] cells 7o4l4c471 & r    
l>g] inn] lay] cells 7i4l4c471 b ^!     
cells1 9 _! lat] developm5t1 d n answ]  
at all to ! two primitive lay]s ( !     
ga/rula1 & ! "n ( ,van ,b5$5's bla/opore
 7,v4,b4b471 = a po9t :]e ! out] lay] ( 
cells is incomplete ov] ! inn]1 only    
commemorates ! au?or%ip ( a misnom]4 ,! 
uni=mity1 or agreem5t1 9 ! developm5t ( 
our o!r v]tebrate types is app>5tly     
dep>t$ f "h4  ,illu/ration3 ,developm5t 
,section #cf4   ,section #cg4 ,z ! egg  
develops1 h[ev]1 we are a/oni%$ to f9d  
an increas+ resemblance to t ( ! f[l4 ,a
 split occurs at "o po9t betwe5 out]    
lay] & inn] lay] cells1 & ! space       
result+ 7,y 9 ,figure #b7 is fill$ by an
 increas+ am\nt ( fluid1 & rapidly      
enl>ges1 s t pres5tly we h ! /ate (     
affairs %[n 9 #c1 9 :i* ! inn] lay]     
cells are ga!r$ toge!r at "o po9t on !  
surface ( ! ovum1 & con/itute ! g]m9al  
area4 ,if1 ) ,hubre*t1 we reg>d ! out]  

lay] cells z an egg membrane1 !re is a  
curi\s p>allelism betwe5 ?is egg & !    
f[l's ! fluid ,y repres5t+ ! yolk2 & !  
inn] lay] cells ! cells ( ! f[l's g]m9al
 area4  ,at any rate1 ! subsequ5t       
developm5t goes f> to ju/ify su* a view4
 ,! inn] cells split into epi-1 meso-1 &
 hypo-bla/1 l ! bla/od]m 9 ! f[l2 !re is
 a primitive /reak & no bla/opore2 an   
amnion arises2 ! yolk sac1 small & full 
( s]\s fluid1 is cut (f j z ! enorm\s   
yolk ( ! f[l is cut (f2 & an allantois  
arises 9 ! same way4 ,!re is no ne$ to  
give special diagrams-- ,figures #c1    
#d;b1 #e1 & #f ( ! f[l w d 9 all        
respects1 except proportion1 = !        
developm5t ( ! rabbit4 ,! diff]5ces are 
su* z we may acc\nt =1 n on !           
supposition t ! rabbit's ovum nev] _h   
any yolk1 b t an abundant yolk has be5  
)drawn f x4 ,! nutrition ( ! embryo by  
yolk has be5 sup]s$$ by "s bett] me?od4 
,! supposition t ! rabbit is desc5d$ f  
ance/ors :i*1 l ! birds & reptiles1 laid
 eggs ) huge quantities ( yolk1 meets e 

circum/ance ( ! case4   ,section #ch4 ,b
 ! allantois & yolk sac ( ! rabbit1 ?\gh
 !y correspond 9 developm5t1 diff]      
entirely 9 function f ! simil> organs ( 
! f[l4 ,! yolk sac is ( ! v smalle/     
nutritive value2 in/ead ( be+ ! sole    
s\rce ( food1 its cont5ts sc>cely avail 
! "y rabbit at all z n\ri%m5t4 ,its     
pres5ce 9 developm5t is difficult to    
acc\nt = except on ! supposition1 t x 0 
once ( f> great] importance4 ,at an e>ly
 /age1 ! outgr[+ allantois1 pu%+ 9 front
 ( x ! s]\s membrane1 is closely appli$ 
to ! l9+ ( ! "m's ut]us4 ,! mat]nal     
ut]us & ! embryonic allantois s5d out   
f+]-l processes into ea* o!r :i*        
int]lock1 & ! tissue betwe5 ! abundant  
bloodvessels 9 !m ?9s d[n to su* an     
ext5t t nutritive mat]ial1 peptones &   
c>bohydrates1 & oxyg5 also1 diffuse     
freely ?r\gh x f "m to foetus199 & c>bon
 dioxide1 wat]1 & urea f ! foetus to !  
"m4 ,! /ructure ?us =m$ by ! union ( !  
wall ( ! mat]nal ut]us1 allantois1 & !  
int]m$iate /ructures is call$ ! plac5ta4

 ,?r\gh its int]m$iation1 ! "y rabbit   
becomes1 z x 71 root$ & p>asitic on !   
"m1 & utilizes h] organs = its own      
alim5tation1 respiration1 & excretion4  
,x gives (f ,,co#b1 ,h#b,o1 & urea1 by !
 plac5ta1 & x receives ,o & elaborat$   
food mat]ial ?r\gh ! same organ4 ,?is is
 ! bett] me?od t has sup]s$$ ! yolk4  99
 ,! embryo4   ,section #ci4 ,9 its lat] 
developm5t1 ! g5]al facts already       
enunciat$ ) reg>d to ! organs ( frog &  
f[l hold1 & :]e frog & f[l are /at$ to  
diff]1 ! rabbit foll[s ! f[l4 ,9 !      
circulation ! left f\r? vascul> ar*     
7second bran*ial7 gives rise to ! aortic
 ar*2 9 ! "r ! correspond+ ar*          
disappe>s1 except s mu* ( x z rema9s z !
 innom9ate art]y4 ,! azygos ve9 7,*apt] 
#c7 -is a ve/ige (- is d]iv$ f ! "r     
po/]ior c>d9al s9us4 ,bo? pulmon>y      
art]ies 9 ! rabbit are d]iv$ f ! left   
six? vascul> ar* 7 f\r? bran*ial74      
,comp>e ,section #cb4 ,! allantois      
altoge!r disappe>s 9 ! adult f[l2 9 !   
adult mammal a portion ( its holl[ /alk 

rema9s z ! ur9>y bladd]1 & ! po9t :]e x 
left ! body is m>k$ by ! umbilicus or   
navel4 ,! umbilical art]ies become !    
small hypoga/ric art]ies on ei!r side ( 
! ur9>y bladd]4 ,!re is no trace ( a    
pronephros at all 9 ! rabbit4   ,section
 #dj4 ,we may note "h ! developm5t ( !  
eye4 ,?is is %[n 9 ,figure #d1 ,%eet    
#bd4 ,a holl[ cup-%ap$ vesicle f ! bra9 
gr[s out t[>ds an at fir/ holl[ cellul> 
+r[? f ! epid]mis4 ,! cavity )9 ! wall (
 ! cup d]iv$ f ! bra9 is oblit]at$1 & ! 
/alk )]s1 ! cup becomes ! ret9a1 & -its 
/alk- !nce fibres gr[ back to ! bra9 to 
=m ! optic n]ve4 ,! cellul> +r[? is !   
l5s4 ,! rema9d] ( ! eye-/ructures are ( 
mesobla/ic orig91 except ! sup]ficial   
epi!lium ( ! cornea4 ,! ret9al cup is n 
complete at fir/ along ! v5tral l9e1 s t
 ! rim ( ! cup1 view$ z 9 ,figure #a1   
r41 is horse%oe %ap$4 -,h5ce ! optic    
n]ve diff]s f o!r n]ves 9 be+           
primitively holl[4- ,9 all o!r s5se     
organs1 z1 = in/ance1 ! olfactory sacs &
 ! e>s1 ! p]cipi5t epi!lium is d]iv$1 f 

! epibla/ directly1 & n indirectly ?r\gh
 ! n]v\s sy/em4 ,^! rem>ks apply to all 
v]tebrate types4   ,section #da4 ,!     
supposition1 t ! g5]al *>act]s ( !      
rabbit's ovum 7 /amp$ ^u x z an h]itage 
f a p]iod :5 ! ance/ors ( ! mammals 7   
egg-lay+ reptiles1 is /r5g!n$ by ! fact 
t ! two l[e/ & mo/ reptile-l ( all !    
mammalia1 ! duck-bill$ platypus & !     
e*idna1 h be5 %[n to dep>t f ! di/9ctive
 mammalian "*1 & to lay eggs4 ,&1 9     
fur!r confirmation ( ?is supposition1 we
 f9d1 9 trac+ ! mammals & reptiles back 
?r\gh ! geological record1 t 9 ! ,p]mian
 & ,triassic rocks !re occur c5tral =ms 
:i* comb9e1 9 a mo/ rem>kable way1      
reptilian & mammalian *>act]i/ics4      
,section #db4 ,9 conclusion1 we w\ld    
e>ne/ly recomm5d ! /ud5t to see m (     
embryological fact ?an :at is giv5 him  
"h4 ,x is see+ & ?9k+1 mu* m ?an read+1 
:i* w enable him to clo! ! b>e t]ms &   
phrases ( embryology ) coh]5t k4 ,9     
,h[es' ,atlas ( ,biology !re is a mu*   
full] s]ies ( figures ( ! frog's        

developm5t ?an c be giv5 "h1 & !y are   
drawn by an abl] h& ?an m9e c pret5d to 
be4 ,!re is also an ,atlas              
d',embryologie1 by ,ma?ias ,duval1 t    
makes ! /udy ( ! f[l's developm5t       
ent]ta9+ & altoge!r delightful4 ,su*    
complete s]ies z ^! are1 f ! nature ( ! 
case1 impossible ) ! rabbit4 ,_m /ud5ts 
:o take up ! subject ( biology d s only 
z an accessory to m ext5d$ "w 9 o!r     
dep>tm5ts ( sci5ce4 ,to su*1 practical  
"w 9 embryology is ei!r altoge!r        
impossible1 or only possibly to a v     
limit$ ext5t4 ,! "t x w consume is mu*  
great]1 & ! intellectual result is      
likely to be f> less ?an ! /udy ( su*   
plates z we h nam$4    ,! ,!ory (       
,evolution  ,section #dc4 ,we h n[      
consid]$ our types1 bo? f ! /&po9t (    
adult anatomy & f embryological data2 & 
we h se5 ?r\gh ! v]tebrate s]ies a      
common /ructure und]ly+ wide div]sity 9 
ext]nal appe>ance & detail$ anatomy4 ,we
 h se5 a c]ta9 int]m$iat5ess ( /ructure 
9 ! frog1 z comp>$ ) ! rabbit & dog-fi%1

 notably 9 ! skull & skeleton1 9 !      
circulation1 9 ! e>1 & 9 ! r$uc$        
myom]es2 & we h se5 t ! rabbit passes 9 
^! respects1 & 9 o!rs1 ?r\gh dog-fi%- & 
frog-l /ages 9 its developm5t1 & ?is    
alone w\ld be q suffici5t to sugge/ t ! 
simil>ities ( /ructure are due to o!r   
causes ?an a primordial adaptation to   
c]ta9 conditions ( life4   ,section #dd4
 ,x has be5 sugge/$ by v excell5t p t ^!
 resemblances are due to "s unexpla9$   
necessity ( adh]5ce to type1 z ?\gh1 !  
p[] t !y assume creat$ ^! animals       
orig9ally1 z !y are n[1 c\pl$ creative  
ability ) a pl5tiful lack ( ideas1 & s  
p]=ce repeat$ itself ) impot5t          
v>iations4 ,on ! o!r h&1 we h !         
supposition t ^! are family lik5esses1 &
 ! m>ks ( a common ance/ry4 ,?is is !   
op9ion n[ accept$ by all zoologi/s (    
repute4   ,section #de4 ,x mu/ n be = a 
mom5t imag9$ t x is impli$ t rabbits are
 desc5d$ f frogs1 or frogs f dog-fi%1 b 
t ^! ?ree =ms are remote c\s9s1 d]iv$ f 
"s anci5t & f> simpl] prog5itor4 ,b s9ce

 bo? rabbit & frog pass ?r\gh phases l !
 adult condition ( ! dog-fi%1 x seems   
probable t ! dog-fi% has rema9$ m l !   
primordial =m ?an ^! two1 & simil>ly1 ! 
frog ?an ! rabbit4   ,section #df4 ,h5ce
 we may inf] t ! mammals 7 ! la/ ( !    
?ree gr\ps1 ( :i* we h tak5 types1 to   
appe> ^u ! e>?1 & t ! fi%es prec$$1 !   
amphibia4 ,work]s 9 an entirely         
indep5d5t prov9ce1 t ( palaeontology1   
completely endorse ?is supposition4 ,!  
fir/ ,v]tebrata to appe> 9 ! fossil     
hi/ory ( ! _w are fi%es2 fi% sp9es &    
placoid scales 7comp>e dog-fi%7 appe> 9 
! ,ordovician rocks4 ,9 ! coal measures 
come ! amphibia2 & 9 ! ,p]mo-triassic   
/rata1 reptile-l mammals4 ,9 ! ,devonian
 rocks1 :i* come betwe5 ! ,silurian & ! 
coal measures1 we f9d v pl5tiful rema9s 
( c]ta9 fi% call$ ! dipnoi1 ( :i* gr\p  
?ree g5]a /ill survive2 !y display1 9   
numb]less features ( _! anatomy1        
transitional *>act]s betwe5 true fi% &  
amphibia4 ,simil>ly1 9 ! ,p]mian come   
mammal-l reptiles1 t po9t also d[nw>d to

 ! amphibia4 ,we f9d1 !re=e1 ! /ory told
 by ! ovum writt5 also 9 ! rocks4       
,section #dg4 ,n[1 :5 ?is fact ( a      
common ance/ry is consid]$1 x becomes   
necess>y to expla9 h[ ?is gradual *ange 
( animal =ms may h be5 br\ght ab\t4     
,section #dh4 ,two subcontr>y           
propositions hold ( ! "y ( any animal4  
,x resembles 9 _m po9ts its p>5t4 ,x    
diff]s 9 _m po9ts f its p>5t4 ,! g5]al  
s*eme ( /ructure & ! great] l9es (      
feature are p>5tal1 inh]it$2 !re are    
also novel & unique details t m>k !     
individual4 ,! fir/ fact is ! law (     
inh]itance2 ! second1 ( v>iation4       
,section #di4 ,n[ ! p>5t or p>5ts1 s9ce 
!y live & bre$1 mu/ be m or less1 b     
suffici5tly1 adapt$ to _! conditions (  
liv+-- m or less fitt$ to ! ne$s ( life4
 ,! v>iation 9 ! "y animal w be "o (    
?ree k9ds3 x w fit ! animal /ill bett]  
to ! conditions "u :i* its k9d live1 or 
x w be a *ange = ! worse1 or x is       
possible to imag9e t ! v>iation-- z 9 ! 
col\r v>iations ( dome/icat$ cats-- w   

affect its prospects 9 life v little4 ,9
 ! fir/ case1 ! probability is t ! new  
animal w get on 9 life1 & bre$1 &       
multiply above ! av]age2 9 ! second1 x  
is probable t1 9 ! competition = food & 
o!r am5ities ( life1 ! disadvantage1    
:atev] x is1 "u :i* ! animal suff]s w   
%ort5 its c>e]1 & abbreviate ! tale (   
its (fspr+2 :ile1 9 ! ?ird case1 an     
av]age c>e] may be expect$4 ,h5ce1      
disreg>d+ accid5ts1 :i* may be elim9at$ 
f ! problem by tak+ _m cases1 !re is a  
cont9ual t5d5cy among ! memb]s ( a      
species ( animals 9 fav\r ( !           
proportionate increase ( ! individuals  
mo/ completely adapt$ to ! conditions "u
 :i* ! species lives4 ,t is1 :ile !     
conditions rema9 un*ang$1 ! animals1    
consid]$ z "o gr\p1 are cont9ually m    
highly p]fect$ to live "u ^? conditions4
 ,& "u *ang$ conditions ! specific =m w 
also *ange4   ,section #ej4 ,! idea (   
?is process ( *ange may be p]haps r5d]$ 
m vivid by giv+ an imag9>y concrete     
in/ance ( its work+4 ,9 ! jungles (     

,india1 :i* pres]ve a /ate ( ?+s :i* has
 exi/$ = immemorial ye>s1 we f9d ! tig]1
 8 /ripes simulat+ jungle re$s1 8       
noiseless approa* le>nt f nature 9      
c\ntless millions ( lessons ( success & 
failure1 8 p]fectly p[]ful claws &      
execution me?ods2 &1 liv+ 9 ! same      
jungle1 & ) him z "o ( ! conditions (   
life1 are small de]1 al]t1 swift1 light 
( build1 inconspicu\s ( col\r1 %>p (    
he>+1 ke5-ey$1 ke5-sc5t$-- because any  
d[nw>d v>iation f ^! attributes means   
swift & c]ta9 dea?4 ,to capture ! de] is
 a condition1 ( ! tig]'s life1 to escape
 ! tig] a condition ( ! de]'s2 & !y play
 a great conte/ "u ^! conditions1 ) life
 z ! /ake4 ,! mo/ al]t de] almo/ always 
escape2 ! lea/ s1 p]i%4   ,section #ea4 
,b conditions may alt]4 ,= in/ance1 :ile
 mo/ ( ^! de] /ill live 9 ! jungle )    
tig]s1 ov] a consid]able area ( _!      
habitat1 "s *ange may be at "w t ?9s !  
jungle1 de/roys ! tig]s 9 x1 & br+s 91  
let u say1 wolves1 z an enemy to ! de]1 
in/ead ( tig]s4 ,n[1 aga9/ ! wolves1 :i*

 d n creep1 b hunt noisily1 & :i* d n   
spr+ sudd5ly ^u prey1 b foll[ by sc5t1 &
 run x d[n 9 packs1 ke5 eyes1 %>p e>s1  
acute p]ceptions1 w be f> less important
 ?an endurance 9 runn+4 ,! de]1 "u ! new
 conditions1 w ne$ co>s] & m p[]ful     
limbs1 & a l>g] *e/2 x w be an advantage
 to be r\gh & big1 in/ead1 ( frail &    
inconspicu\s1 & ! e>s & eyes ne$ n be s 
l>ge4 ,! old ref9em5ts w mean weakness &
 dea?2 any v>iation along ! l9e ( size &
 co>s5ess w be advantage\s4 ,slight &   
delicate de] w be cont9ually be+ kill$1 
r\gh] & /rong] de] cont9ually escap+4 ,&
 s gradually1 "u ! new circum/ances1 if 
!y are n suffici5t to ext]m9ate !       
species1 ! f9] *>act]i/ics w be         
elim9at$1 & a new v>iety ( our old      
jungle de] w arise1 &1 if ! sep>ation & 
contra/ ( ! conditions is suffici5tly   
great & p]man5t1 we may1 at la/1 9 !    
c\rse ( ages1 get a new k9d ( de]       
specifically diff]5t 9 its limbs1 body1 
s5se organs1 col\r1 & in/9cts1 f ! de] t
 live 9 ! jungle4 ,& ^! latt] w1 on _!  

side1 be /ill cont9ually m p]fect$ to ! 
jungle life !y are lead+4   ,section    
#eb4 ,take a wid] range ( "t & va/]     
*anges ( condition ?an ?is1 & x becomes 
possible to imag9e h[ ! social cattle-- 
) _! unit$ front aga9/ an enemy1 fi]ce  
onslaught1 & _! g5]al adaptation to     
prairie life-- h diff]5tiat$ f !        
ance/ors ( ! slight & timid de]2 h[ !   
pati5t camel1 ) 8 /orage hump1 wat]     
/orage1 & feet padd$ aga9/ hot s&1 has  
be5 m\ld$ by ! necessity ( des]t life f 
! same ance/ral =m4 ,& s we may "w back1
 & l9k ^! =ms1 & o!r purely veget>ian   
fe$]s1 ) remot] c\s9s1 ! ance/ral hogs4 
,work+ 9 ?is way1 we pres5tly get a     
glimpse ( a possible yet remot]         
connection ( all ^! ho($ & ma9ly        
veget>ian animals1 ) c]ta9 c5tral types 
t c>ry u across to ! omnivor\s1 &1 9 "s 
cases1 almo/ entirely veget>ian be>s1 & 
to ! great & prosp]\s family ( claw$1   
meat-eat]s4 ,& ?us we elucidate1 at la/1
 a ?read ( blood relation%ip betwe5 !1  
at pres5t1 /rongly contra/$ &           

antagoni/ic de] & tig]1 & pass+ !nce    
into /ill wid] g5]alizations1 x w\ld be 
possible to connect ! rabbit play+ 9 !  
sun%9e1 ) ! frog 9 ! dit*1 ! dog-fi% 9 !
 sea-wat]s & ! lancelet 9 ! s&4 ,= !    
transition f dog-fi% to rabbit diff]s f 
! transition f "o species ( de] to ano!r
 only 9 magnitude3 x is an affair ( va/ 
epo*s in/ead m]ely ( ?\s&s ( ye>s4      
,section #ec4 ,x w\ld1 h[ev]1 be beyond 
! design ( ?is book to c>ry our         
demon/ration ( ! cr$ibility ( a common  
ance/ry ( animals /ill fur!r back4 ,b we
 may po9t out "h t x is n a !ory1 bas$  
m]ely ^u "o set ( facts1 b "o s+ul>ly   
ri* 9 confirmation4 ,we c con/ruct1 on  
purely anatomical gr\nds1 a !oretical   
p$igree4 ,n[ ! indep5d5t /udy (         
embryology sugge/s exactly ! same       
p$igree1 & ! entirely indep5d5t te/imony
 ( palaeontology is precisely 9 h>mony )
 ! already confirm$ !ory arriv$ at 9 ?is
 way4   ,section #ed4 ,x is 9 !         
demon/ration ( ?is wond]ful unity 9     
life1 only ! m confirm$ ! m exhau/ive   

our analysis becomes1 t ! educational   
value & human int]e/ ( biology *iefly   
lies4 ,9 ! place ( disconnect$ species (
 animals1 arbitr>ily creat$1 & a belief 
9 ! settl$ inexplicable1 ! /ud5t f9ds an
 enlight5+ realization ( uni=m & active 
causes b5ea? an app>5t div]sity4 ,& ! _w
 is n made & dead l a c>dbo>d model or a
 *ild's toy1 b a liv+ equilibrium2 & e  
day & e h\r1 e liv+ ?+ is be+ weigh$ 9 !
 balance & f\nd suffici5t or want+4     
,our little book is ! m]e/ beg9n+ 9     
zoology2 we h /at$ "o or two gr\ps (    
facts & made "o or two sugge/ions4 ,!   
great ?+s ( ! sci5ce ( ,d>w91 ,huxley1  
,wallace1 & ,balf\r rema9 ma9ly untold4 
,9 ! book ( nature !re are writt51 =    
in/ance1 ! triumphs ( survival1 ! trag$y
 ( dea? & ext9ction1 ! tragi-com$y (    
degradation & inh]itance1 ! gruesome    
lesson ( p>asitism1 & ! political satire
 ( colonial organisms4 ,zoology is1     
inde$1 a philosophy & a lit]ature to ^? 
:o c read its symbols4 ,9 !             
contemplation ( beauty ( =m & (         

me*anical beauty1 & 9 ! intellectual    
delight ( trac+ & elucidat+ relation%ips
 & criticis+ appe>ances1 !re is also =  
_m a great rew>d 9 zoological /udy4 ,)  
an increas+ k ( ! facts ( ! =m ( life1  
!re gradually appe>s to ! /ud5t !       
realization ( an entire unity %ap$ out  
by _! c\ntless1 & (t5 beautiful1        
div]sity4 ,& at la/1 9 ! place ( !      
manifoldness ( a fair or a m>9e /ore1 ! 
/ud5t ( sci5ce p]ceives ! inf9ite v>iety
 ( "o consi/5t & compreh5sive ,be+-- a  
realization to :i* no o!r /udy leads him
 at pres5t s surely4  ,to ! /ud5t :o    
feels incl9$ to amplify ?is brief outl9e
 ( ,v]tebrate ,anatomy1 we may m5tion ! 
foll[+ books3 ,wi$]%eim's & ,p>k]'s     
,v]tebrates1 ,huxley's ,anatomy ( !     
,v]tebrata1 ,fl[]'s ,o/eology ( !       
,mammalia1 ,wallace's ,di/ribution1     
,ni*olson & ,lyddek]'s ,palaeontology   
7,volume #b71 ! summ>ies 9 ,rolle/on's  
,=ms ( ,animal ,life 7:]e a bibliography
 w be f\nd71 & ,balf\r's ,embryology4 ,b
 read+ )\t practical "w is a dull &     

unpr(itable me?od ( /udy4    ,que/ions  
on ,embryology     ,all ^! que/ions 7   
actually set at ,london ,univ]sity      
,exam9ations4    ,9 ,bo? ,editions4  #a4
 ,describe ! *anges 9 ! egg-cell :i*    
prec$e f]tilization2 describe ! process 
( f]tilization & ! =mation ( ! prim>y   
cell-lay]s1 z exhibit$1 9 ?ree ( !      
animal types kn[n to y4 ,:at is !       
noto*ord1 & h[ is x develop$ 9 ! frog8  
#b4 ,describe ! e>ly /ages 9 !          
developm5t ( ! egg ( ! f[l z f> z !     
closure ( ! neural groove4 ,h[ d y      
acc\nt = ! primitive /reak8  #c4        
,describe ! cleavage & ! surface        
appe>ances ( ! egg ( ! frog & ( !       
rabbit1 up to ! "t :5 ! fir/ gill-slits 
appe> 9 ! embryo4 ,give illu/rative     
diagrams ( :at y describe4  #d4         
,describe ! /ructure & cleavage ( ! ovum
 7a7 ( ! frog1 7b7 ( ! f[l1 & 7c7 ( !   
rabbit4 7d7 ,expla9 z f> z possible !   
diff]5ces 9 ! cleavage ( ^! ?ree eggs4  
7e7 ,po9t out h[ ! embryo is n\ri%$ 9   
ea* case1 & 7f7 describe ! con/itution (

 ! plac5ta 9 ! rabbit4  #e4 7a7 ,:at are
 ! protov]tebrae8 7b7 ,h[ does !        
noto*ord orig9ate 9 ! frog8 7c7 ,h[ are 
! v]tebrae laid d[n 9 ! tadpole8 7d7    
,describe ! v]tebral column ( ! adult   
frog4 7e7 ,9 :at important respects d ! 
c5tra ( ! v]tebrae ( ! frog1 ! dog-fi%1 
& ! rabbit diff] f "o ano!r8  #f4 ,give 
an acc\nt ( ! m important features 9 !  
developm5t ( ! frog4  #g4 ,:at tempor>y 
organs are develop$ 9 ! embryo frog :i* 
are abs5t f ! embryo bird & mammal1 &   
:at 9 ! two latt] :i* are abs5t f ! =m]8
  #h4 ,draw diagrams1 ) ! p>ts nam$1 ( !
 he>t & great art]ies ( ! frog1 giv+    
descriptions only 9 s f> z is necess>y  
to expla9 y\r diagrams2 trace !         
developm5t ( ^! /ructures 9 ! tadpole2  
po9t out p>ticul>ly 9 :i* ( ! embryonic 
visc]al 7bran*ial7 ar*es ! great art]ies
 ( ! adult run4  #i4 ,trace ! hi/ory ( !
 po/-oral gill-slits & _! accompany+    
c>tilag9\s b>s & vascul> ar*es 9 ! frog1
 f[l1 & rabbit4  #aj4 ,give a %ort      
acc\nt1 ) illu/rative figures1 ( ! mode 

( =mation ( ! prim>y g]m9al lay]s 9     
amphioxus & 9 ! frog4 ,:at explanation c
 y give ( ! diff]5ces betwe5 ! two      
cases8  #aa4 ,give a %ort acc\nt1 )     
diagrammatic figures1 ( ! pr9cipal      
*anges :i* occur 9 ! circulatory &      
respiratory organs dur+ ! metamorphosis 
( ! tadpole into ! frog4  #ab4 ,h[ d    
protozoa diff] f high] animals 7metazoa7
 z reg>ds 7a7 /ructure1 7b7             
reproduction8 ,comp>e ! process (       
fission 9 an amoeba ) ! segm5tation ( ! 
ovum 9 amphioxus1 po9t+ out !           
resemblances & diff]5ces betwe5 ! two   
cases4    -,miscellane\s ,que/ions      
,mo/ ( ^! que/ions 7 actually set at !  
,biological    ,exam9ations ( ,london   
,univ]sity4 ,9 ,bo? ,editions4  #a4     
,describe 7a7 ! dige/ive1 7b7 !         
circulatory1 7c7 ! excretory1 & 7d7 !   
reproductive organs ( ! amphioxus4  #b4 
,describe ! /oma* & inte/9es ( ! dog-fi%
 & rabbit1 & po9t out 9 :at way _!      
diff]5ces are connect$ ) diet4  #c4     
,describe ! me*anism ( respiration 9 !  

adult frog1 & contra/ x ) t ( ! tadpole4
  #d4 ,give an acc\nt ( ! /ructure ( !  
epid]mis & its outgr[?s 9 ! frog & !    
rabbit4  #e4 ,describe ! organs (       
circulation 7he>t & ma9 art]ies & ve9s7 
& respiration 9 ! frog 9 its mature &   
immature /ates4  #f4 ,give a brief      
acc\nt ( ! physiology ( respiration4    
,describe fully ! means by :i*          
respiration is effect$ 9 ! foll[+       
animals3-- frog1 amphioxus1 rabbit1 &   
dog-fi%4  #g4 ,describe ! m9ute /ructure
 ( ! blood ( ! rabbit1 frog1 &          
amphioxus4  #h4 ,describe & illu/rate by
 means ( sket*es ! *ief po9ts ( diff]5ce
 betwe5 ! skeleton ( ! rabbit z a       
typical mammal1 & t ( ! common frog z a 
typical amphibian4  #i4 7a7 ,expla9 :at 
is meant by ! t]m c5tral n]v\s sy/em4   
7b7 ,describe ! tissue elem5ts :i* ent] 
into its composition4 7c7 ,expla91 z f> 
z y c1 ! function ( ea* /ructure        
describ$4 7d7 ,h[ is ! c5tral n]v\s     
sy/em develop$ 9 ! frog1 & 7e7 9 !      
rabbit8 7f7 ,:at conclusions may be     

drawn f ! facts /at$ z to ! orig9 ( !   
c5tral n]v\s sy/em 9 evolution8  #aj4   
,give an acc\nt ( ! /ructure 7includ+   
hi/ology7 & ( ! functions ( ! sp9al cord
 & sp9al n]ves ( ! frog4  #aa4 ,give a  
description ( ! m9ute /ructure & *emical
 *>act]s ( ! foll[+ tissues z se5 9 !   
frog3-- c>tilage1 bone1 muscle4 ,f :i* (
 ! prim>y cell-lay]s ( ! embryo are !y  
respectively develop$8  #ab4 ,:at       
sub/ance is excret$ by ! r5al organ ( a 
frog1 & :at relation does ?is sub/ance  
be> to ! g5]al life ( ! organism8       
,describe ! p>ts by :i* simil> excretion
 is believ$ to be effect$ 9 amoeba1     
hydra1 e>?worm1 mussel1 & lob/]4  #ac4  
,describe1 ) illu/rative sket*es1 !     
/ructure ( ! connective tissue1         
c>tilage1 & muscul> tissue ( a frog4    
,also describe ! /ructure ( ! muscul>   
tissue ( ! lob/] & snail4  #ad4 ,give 9 
acc\nt ( ! m important features 9 !     
developm5t ( ! frog4  #ae4 ,describe &  
comp>e ! /ructure ( ! r5al organs 9 a   
frog & a rabbit4  #af4 ,give an acc\nt (

 ! /ructure ( ! g5ito-ur9>y organs ( !  
frog4 ,comp>e ^! organs ( ! frog ) ^? ( 
! dog-fi% & ( ! rabbit4 ,di/+ui% 9 ea*  
case ! conditions ( ! two sexes1 &      
describe briefly ! microscopic /ructure 
& developm5t ( ! ova & ( ! sp]matozoa4  
#ag4 ,describe1 ) diagrams1 ! arrangem5t
 ( ! ur9>y & g5]ative organs 9 ! male ( 
7a7 ! rabbit1 7b7 ! dog-fi%1 & 7c7 !    
frog2 7d7 po9t out ! mo/ important      
diff]5ces betwe5 !m4  #ah4 7a7 ,describe
 ! /ructure ( ! ov>ian egg ( ! rabbit1  
7b7 & ( ! pigeon1 7c7 & ( ! frog2 7d7 f 
:at "p ( ! embryo d !y orig9ate8 7e7    
,:at is ! /ructure & orig9 ( ! ov>ian   
follicle 9 ! rabbit1 & 7f7 ( ! ov>ian   
/roma8 7g7 ,:at is ! granulosa & :at !  
zona pellucida8  #ai4 ,describe !       
pre-segm5tation *anges1 mode (          
impregnation1 & e>ly /ages ( developm5t 
9 ! ovum ( ! frog1 z f> z ! closure ( ! 
neural canal4  #bj4 ,illu/rate1 )       
diagrams1 f ! /ructure ( typical        
organisms1 ! pr9ciple ( repetition (    
simil> p>ts4    -,note on ,mak+         

,comp>isons  ,/ud5ts prep>+ =           
exam9ations are frequ5tly tr\bl$ by     
comp>ison que/ions4 ,tabulation is (t5  
recomm5d$1 b we are incl9$ to fav\r a r 
m flexible plan ( m>k+ (f diff]5ces &   
resemblances4 ,9 tabulation a           
consid]able loss ( "t is occasion$ by   
writ+ d[n ! features ( bo? ! ?+s comp>$1
 & ?is is a s]i\s consid]ation = !      
exam9ee4 ,we advise him !re=e1 fir/1 if 
he possibly c1 to draw side by side & 9 
correspond+ positions ! two ?+s "u      
consid]ation1 & !n1 go+ ov] !m 9 a      
me?odical way1 to /ate simply ! diff]5ce
 betwe5 ea* homolog\s "p4 ,we app5d z   
examples ?ree te/ answ]s actually       
submitt$ 7) figures7 9 ,correspond5ce   
"w3--  #a4 ,comp>e ! bra9 ( ! frog ) t (
 ! rabbit4     ,9 ! frog's =e-bra9--    
,! olfactory lobes are fus$ 9 ! middle  
l9e4        ,!re is no corpus callosum1 
nor is !re a middle commissure to       
! ?ird v5tricle4        ,! c]ebral      
hemisph]es are n convolut$1 &1 look$ at 
f       ! dorsal aspect1 d n hide !     

?alam5cephalon & mid-bra94        ,!    
p9eal gl& lies 9 ! cranial wall & n     
deeply betwe5       ! hemisph]es1 & its 
/alk is long] & tilts =w>d4     ,9 !    
mid-bra9--        ,! optic lobes are    
two1 in/ead ( be+ corpora quadrigem9a1  
& holl[4     ,9 ! h9d-bra9--        ,!  
c]ebellum is a v small transv]se b&1 &  
has no       lat]al p>ts4        ,!     
m$ulla is relatively l>g]4        ,!re  
are no sp9al accessory nor hypoglossal  
n]ves to !       bra94  #b4 ,comp>e !   
v]tebrae ( dog-fi%1 rabbit1 & frog4     
,! c5tra ( ! dog-fi% are -opi/ho-       
amphi-coel\s    7i4e41 holl[ at ei!r    
end74     ,! c5tra ( ! rabbit are       
flat-fac$4     ,! c5tra ( ! frog are    
procoel\s 7holl[ 9 front74     ,!       
noto*ord p]si/s betwe5 ! c5tra 9 !      
dog-fi% &    rabbit1 )9 ! c5tra 9 frog4 
,! c5tra ( ! rabbit h epiphyses1 abs5t 9
 ! dogfi%    & frog4     ,! transv]se   
processes ( ! rabbit typically be> ribs4
    ,%ort ribs occur 9 ! dog-fi%1 b _!  
homology ) ^?    ( ! rabbit is d\btful4 

,! frog has no ribs4     ,! int]neural  
plates are peculi> to ! dog-fi% 9 ?is   
comp>ison4  #c4 ,comp>e ! skull ( ! dog 
) t ( ! frog4     ,! ,bra9 ,case--      
,( ! frog is a cyl9drical box1 f :i* !  
otic capsules       project conspicu\sly
 on ei!r side4 ,x conta9s only two      
ossifications 9 its c>tilag9\s sub/ance 
7! sph5-e?moid       & ! ex-occipital71 
be+ protect$ by ! membrane bones1       
! p>ieto-frontals above & ! p>asph5oid  
bel[4        ,9 ! mammal x is enorm\sly 
inflat$1 & ! otic capsules       are    
imb$d$ 9 its wall4 ,!re are supra- &    
basi- z well z       ex-occipital bones2
 ! p>a-sph5oid is 78 entirely7 gone1 &  
its place is tak5 by ! basi- &          
pre-sph5oids1 & !       lat]al walls    
conta9 fre% pair$ ossifications1 ! ali- 
&       orbito-sph5oids-- all c>tilage  
bones4 ,! sph5e?moid is       p]haps    
repres5t$ 9 "p by ! e?moid4        ,z a 
result ( ! inflation ( ! bra9-case1 !   
squamosal1       :i* slopes d[nw>d &    
outw>d 9 ! frog1 & ov]lies !            

c>tilag9\s susp5sorium 7quadrate        
c>tilage71 has become a       con/itu5t 
( ! bra9-case wall1 & slopes d[nw>dly & 
94     ,jaw ,susp5sion--        ,! po9t 
( atta*m5t ( ! jaw has %ift$ outw>d1 & !
       orig9al susp5sorial c>tilage 7!  
quadrate7 has tak5 on a new       & m9or
 function z ! incus ( ! middle e>-- !   
squamosal       sup]s$+ x z ! susp5sory 
"p4     ,l[] ,jaw--        ,di/9ct bones
 9 ! frog2 "o mass 9 ! dog4     ,otic   
,capsule--        ,position z specifi$4 
,"o c5tre ( ossification 9 ! frog       
=m+ pro-otic2 sev]al fuse toge!r & =m   
p]iotic ( !       dog4        ,!re is no
 bulla & no ext]nal e> 9 ! frog4        
,palate--        ,9 ! frog ! po/]ior    
n>es op5 into ! front ( ! m\?4       ,9 
! dog ! maxillae & palat9es s5d plates  
d[n & 9 7!       palat9e plates7 to cut 
(f a nasal passage f ! re/ ( !          
buccal *amb]1 & c>ry ! po/]ior n>es back
 to ! ph>ynx1       ?us cutt+ ! vom]s (f
 f ! m\? ro(4        ,! pt]ygoids 9 !   
dog are mu* r$uc$1 & d n rea* back      

to ! susp5sorium4        ,! frog has no 
la*rymal bone4    -,syllabus ,(         
,practical ,"w  ,we w\ld impress ^u !   
/ud5t at ! outset ! importance ( "s     
prelim9>y read+ be=e dissection is      
und]tak54 ,no "o w\ld dream ( attempt+  
to explore a des]t$ city )\t "s previ\s 
/udy ( maps & guide-books1 b we f9d aga9
 & aga9 /ud5ts und]tak+ to explore !    
complicat$ anatomy ( a v]tebrat$ animal 
)\t ! slighte/1 or only ! slighte/1     
prep>atory read+4 ,?is is entirely a    
mi/ake4 ,a /ud5t %\ld be famili> ) !    
nom5clature ( ! /ructures he            
contemplates exam9+1 he %\ld h "s idea (
 _! mutual relations & functions1 or 8  
att5tion w inevitably be div]t$ by !    
difficulty ( new names & physiological  
que/ion+s to ! neglect ( 8 dissection1 &
 t c>eful obs]vation ( =m & mutual      
position :i* is ! ess5tial object (     
dissection4 ,on ! o!r h&1 x is equally  
necess>y-- p]haps m s-- to w>n /ud5ts   
aga9/ ! booki% fallacy1 & to assure !m (
 ! absolute impossibility ( realiz+     

biological facts f read+ alone4         
,practical "w c alone confirm & complete
 ! k to :i* ! text-book is ! guide4 ,9  
sci5tific tea*+ x may sometimes be      
conv5i5t = ! ?\ght to prec$e ! ?+1 b    
until ! ?+ has be5 dealt ) ! k ga9$ is  
an unsatisfactory & un/able possession4 
,= su* dissection z ! subject-matt] (   
?is book requires1 ! foll[+ appliances w
 be ne$$3--     7a7 ,two or ?ree        
scalpels ( v>i\s sizes4     7b7         
,scissors1 :i* mu/ tap] gradually1 h    
/raight blades1 &    be po9t$ at ! ends1
 & :i* mu/ bite "r up to ! tips 7or     
!y are useless74 ,two pairs1 small &    
l>ge1 are advisable4     7c7 ,=ceps1 :i*
 mu/ hold firmly1 & meet truly at !     
po9ts4     7d7 ,two ne$les set 9 wood5  
h&les4     7e7 ,an ord9>y wat*mak]'s    
eye-glass is v helpful1 b n             
indisp5sable4     7f7 ,a dissect+ di%-- 
an ord9>y pie di% w d-- into :i*        
melt$ p>aff9 wax has be5 p\r$1 to ! dep?
 (1 say1    ?ree-qu>t]s ( an in*1 &     
all[$ to solidify4 7,?is wax may    be  

black5$ by mixture ) lampblack4 ,if !   
wax floats up at any    "t1 x c1 (      
c\rse1 be remelt$4 ,or x may be load$ ) 
lead47     7g7 ,a r\gh table or bo>d 7= 
! rabbit & dog-fi%74     7h7 ,blanket   
p9s1 & ord9>y p9s4     7i7 ,a pickle or 
o!r wide-m\!d j>1 & "s common1 me?ylat$ 
_s4     7j7 ,a microscope1 ) l[ p[] ( #a
 in* or #a_/b in*1 & high    p[] #a_/f  
in* or #a_/d in*4 ,glass slips & cov]   
glasses1 & a    bottle ( v weak 7#a p]  
c5t47 solution ( salt4  ,animals =      
dissection may be obta9$ f ! recognis$  
deal]s1 :o usually adv]tise 9 su*       
sci5tific p]iodicals z ,nature1 ,natural
 ,sci5ce1 & ,k4 ,s9el 7naturali/1       
,j]sey7 is ! mo/ satisfactory deal] 9   
dog-fi% 9 our exp]i5ce2 ,bolton         
7,malv]n7 w supply ,amphioxus ?r\gh !   
po/2 frogs & rabbits may be obta9$      
any:]e4 ,! tame v>iety ( rabbit is q    
satisfactory = ! purpose ( dissection4  
,! foll[+ notes may possibly be ( "s use
 to ! /ud5t2 !y foll[ ! l9es ( "w       
arrang$ by ! au?or = ! ev5+ classes ( ! 

,univ]sity ,tutorial ,college1 classes  
consid]ably re/rict$ z reg>ds "t1 :5    
comp>$ ) ord9>y laboratory work]s4 ,mo/ 
( ! sections bel[ occupi$ ab\t ?ree     
h\rs1 b = a /ud5t work+ alone !y are m  
likely to take f\r or five1 & ev5 !n x  
is n probable t !y w be s satisfactory z
 if p]=m$ "u skill$ sup]vision4 ,!re are
 _m po9ts extremely difficult to convey 
v]bally :i* are elucidat$ at once by    
actual demon/ration ^u a specim54 ,ea* (
 ^! dissections %\ld be repeat$1 & x is 
well if a diff]5t condition ( ! type is 
select$ = ! repetition-- an old "o if ! 
fir/ specim5 0 immature1 a female if !  
fir/ 0 a male4   -,! ,rabbit  ,may be   
kill$ by *lor(orm1 or potassium cyanide1
 or dr[n$4 ,x may also be readily       
suffocat$ ) h\se-hold gas4 ,x %\ld be   
kill$ imm$iately be=e use1 z o!rwise !  
ga/ric juice attacks ! wall ( ! /oma*1 &
 ! dissection is1 9 consequ5ce1 r5d]$   
extremely disagreeable4 ,a v "y rabbit  
is unsatisfactory z reg>ds ! g5italia1 b
 o!rwise !re is no objection to a little

 "o1 & x has ?is advantage-- t x may be 
imm]s$ m conv5i5tly "u wat]1 9 a l>ge   
pie di%1 = purposes ( f9e dissection4 ,!
 ext]nal features ( ! animal %\ld be    
exam9$3 eyelids1 :isk]s & tee?1 toes1   
anus1 p]9eal space on ei!r side ( !     
same1 urog5ital op5+1 & position ( !    
ribs1 v]tebral column1 & limb girdles   
b5ea? ! sk9 %\ld be made out4 ,!n !     
animal %\ld be p9n$ out ?r\gh ! legs1 ! 
v5tral surface upp]mo/1 ! sk9 op5$ up   
along ! middle l9e f pelvic girdle to   
symphyses ( jaw2 sep>at$ f ! body wall  
bel[ by means ( ! h&le ( a scalpel1 &   
turn$ back2 & !n ! abdom9al wall %\ld be
 cut into & two flaps p9n$ back to      
expose its cont5ts4 ,note ! xiphi/]num4 
,! caecum & colon w be recognis$        
7,section #af72 ! /oma*1 ! "r & left    
c5tral1 & left lat]al lobes ( ! liv] w  
probably be app>5t2 & ! ur9>y bladd]    
7especially if di/5d$7 9 ! middle l9e   
beh9d4 ,)\t any fur!r dissection1 b     
simply by turn+ ! p>ts ov]1 all !       
/ructures ( ! abdom5 9 ,figure #a1 ,%eet

 #a1 w be id5tifi$4 ,seek especially = &
 note p>ticul>ly1 ! gall bladd]1 bile   
duct1 & portal ve91 pancreatic duct1    
sacculus rotundus1 v]mi=m app5dix1      
uret]s 7by pull+ ur9>y bladd] =w>d71    
g5ital ducts 7loop+ ov] uret]s71 sple51 
kidneys1 & adr5als4 ,! v5a cava inf]ior 
is se5 dorsally4 ,! g5ital duct guides !
 /ud5t to ! g5ital gl&2 if ! subject is 
a male1 ! te/es may be expos$ by        
dissection1 or by pull+ ! vas def]5s    
g5tly ! scrotal sac w be turn$ inside   
out1 & ! te/es br\ght into view4 ,! ov>y
 lies expos$ )\t dissection po/]ior to !
 kidney4 ,exam9e all ?is c>efully1 &    
make small sket*es ( po9ts ( int]e/-- ! 
duod5al loop & ! pyloric end ( ! /oma*1 
= in/ance2 ! meet+ ( colon1 caecum1 &   
sacculus rotundus aga92 or ! ur9>y      
bladd] & adjac5t p>ts4 ,note ! dorsal   
aorta & v5a cava & _! connexions beh9d4 
7,comp>e figure ( circulation47 ,cut    
?r\gh pelvic girdle1 & remove "o h9d    
leg1 to see bladd] & g5ital ducts bett] 
7comp>e ,%eet #aj74 ,wa% away any blood 

t may fl[4 ,turn all ! inte/9es ov] to !
 animal's "r1 & see ! dorsal aorta & v5a
 cava inf]ior ( ! abdom51 ! inf]ior     
mes5t]ic art]y1 & ! sp]matic 7or ov>ian7
 art]y 7comp>e1 ( c\rse1 ) figure 9     
book74 ,9 front1 imm$iately dorsal to ! 
sple51 is a v>iable quantity (          
lymphoidal tissue1 :i* mu/ be v c>efully
 cle>$ to see ! sup]ior mes5t]ic &      
coeliac art]ies4 ,sep>ate ,spigelian    
lobe f /oma*1 & look = vagus n]ve       
desc5d+ by oesophagus1 sol> plexus ar\nd
 ! sup]ior mes5t]ic art]y1 & ?r[n up v  
di/9ctly by ! purple v5a cava inf]ior   
b5ea?1 & ! splan*nic n]ve4 ,to see !    
abdom9al sympa!tic beh9d1 g5tly remove !
 p]itoneum t lies on ei!r side ( !      
aorta2 blood-vessels w be se5 runn+ 9   
betwe5 ! v]tebral bodies1 & ! sympa!tic 
*a91 ) its ganglia1 made out v di/9ctly1
 z x runs across !m longitud9ally4 ,n[  
cut oesophagus j 9 front ( /oma*1 & cut 
! rectum1 cut ?r\gh ! mes5t]y support+ !
 inte/9e1 & remove & unravel alim5t>y   
canal2 cut op51 wa% out1 & exam9e caecum

 & /oma*4 ,ble$+ to a consid]able ext5t 
is inevitable1 *iefly f ! portal ve94 ,!
 liv] _h bett] rema9 if ! same rabbit is
 to s]ve = ! second dissection4  ,second
 ,dissection4-- ,sk9 front ( ?orax &    
neck4 ,note subclavian ve9s runn+ out to
 =e limbs-- avoid cutt+ ^!4 ,cut ?r\gh  
ribs & remove front ( ?orax1 to expose  
its cont5ts2 cut up middle l9e ( neck1 &
 cle> (f small muscle b&s1 to expose    
bloodvessels2 pick away c>efully :atev] 
is left ( ?ymus gl&2 make out /ructure (
 he>t & blood-vessels1 z describ$1 9    
,*apt] #c2 note l>ynx & tra*ea4 ,n[     
proce$ to ! exam9ation ( ! n]ves ( ?is  
region4 ,see phr5ic n]ve1 by v5a cava   
inf]ior1 & betwe5 he>t & lungs1 &       
sympa!tic1 runn+ ov] ! heads ( ! ribs4  
,by ! common c>otids w be f\nd ! l>ge   
:ite vagus n]ve1 ! greyi% sympa!tic1 & a
 small bran* ( ,x41 ! depressor4 ,make  
out bran*es ( ,x4 nam$ 9 text4 ,! big   
:ite c]vical sp9al n]ves w be evid5t    
dorsally4 ,cle> =w>d into ! angle betwe5
 ! jaw & ! bulla tympani1 to see ,,xii4 

& ,,xi42 ,,ix4 w be f\nd1 ly+ deep]1    
dorsal to ! c>otid art]y & body ( !     
hyoid4 ,comp>e ) figure giv5 ( ?is4 ,sk9
 ! *eek1 & see ,,vii4 runn+ ov] x4 ,cut 
?r\gh mal> & remove x2 cut ?r\gh l[]    
jaw-bone & turn x back1 to see ! ?ird   
bran* ( ! fif? n]ve on its inn] side2   
exam9e ! muscles ( eyeball1 & remove x1 
to expose ! fir/ & second bran*es (     
,v4-- ! latt] is especially deep )9     
orbit4 ,remove1 op51 wa% out1 & exam9e !
 he>t4 ,%ave (f ! dorsal wall ( cranium1
 to expose hemisph]es ( bra91 & !n put !
 head 9 /rong _s = a week or s4 ,) a    
second rabbit1 ?is dissection may       
advantage\sly be v>i$ by remov+ ! l[]   
jaw1 cutt+ -up- ?r\gh s(t palate1 &     
obs]v+ op5+s ( ! ,eu/a*ian tubes4 ,!    
tonsils 7on ! v5tral side ( ! s(t       
palate7 mu/ n confus$ ) ^!4 ,! he>t %\ld
 also be cut out1 wa%$ out & exam9$     
7,comp>e ,sections #ch1 #dd47  ,?ird    
,dissection4-- 7,be=e ?is is p]=m$ !    
mammalian skull %\ld h be5 /udi$ &      
exam9$47 ,take ! head ( a rabbit1 ! bra9

 ( :i* has be5 h>d5$ by _s1 & c>efully  
remove cranium2 be p>ticul>ly c>eful 9  
pick+ away ! p]iotic bone1 on acc\nt ( !
 flocculi ( c]ebellum4 ,x is difficult  
to avoid injury to ! pituit>y body      
emb$d$ 9 ! basisph5oid bone4 ,exam9e ) !
 help ( ,%eet #h4 ,make ! sections !re  
indicat$4   -,! ,frog  ,may be kill$ by 
dr[n+ 9 dilute me?ylat$ _s1 or by       
*lor(orm4 ,take a rec5tly-kill$ frog1 & 
exam9e a drop ( its blood1 spread out on
 a glass slip1 "u ! microscope2 comp>e x
 ) y\r own4 ,be=e us+ ! high p[]1 put a 
cov] glass ov] ! object1 ( c\rse4       
,scrape ! ro( ( ! m\? ( ! frog g5tly1 to
 obta9 ciliat$ epi!lium2 & m\nt 9 v weak
 salt solution-- ! cilia w /ill be      
active4 ,squam\s epi!lium may be se5 by 
! /ud5t simil>ly scrap+ ! int]ior ( 8   
own *eek4 ,take a piece ( muscle f "o ( 
! frog's limbs1 tease out ) ne$les ^u a 
glass slip1 & exam9e4 ,to see !         
/riations cle>ly1 ! high p[] w be ne$$4 
,comp>e a piece ( muscle f ! wall ( !   
alim5t>y canal4 ,simil>ly exam9e n]ve & 

connective tissue4  ,fir/ ,dissection4--
 ,p9 out ! frog 9 a dissect+ di%1 v5tral
 surface upp]mo/1 & cov] ) wat]4 ,op5 up
 ! sk9 along ! mid-v5tral l9e4 ,note !  
l>ge sub-cutane\s lymph spaces1 ! pelvic
 & pectoral girdles1 & ! ant]ior        
abdom9al ve94 ,cut into ! body cavity on
 "o side ( ?is latt]1 cut across 9 front
 ( :]e ! ve9 dips d[n to liv]1 & peel ! 
body wall away f x4 ,! xiphi/]num w     
probably be cut 9 ?is op]ation4 ,9 e>ly 
spr+ ! females are greatly di/5d$ ) ova1
 & ! great] portion ( ! ov>y may1 )     
advantage1 be remov$4 ,! oviduct is dead
 :ite !n1 & l>g] & mu* m 9 evid5ce ?an !
 7p9ki%7 inte/9e ev54 ,turn ov] !       
visc]a1 & comp>e ) ,%eet #aa2 "o lung is
 (t5 f\nd greatly inflat$1 & !n projects
 back into ! body cavity2 ! /oma* is1 9 
"s cases1 pu%$ =w>d & hidd5 beh9d !     
%\ld] girdle4 ,obs]ve ! allantoic       
bladd]1 ! sple51 gall bladd]1 portal    
ve91 & pancreas4 ,by squeez+ ! gall     
bladd] g5tly1 ! bile duct w be inject$ )
 bile1 & w be app>5t if ! /oma* is turn$

 ov]4 ,! oesophagus1 j 9 front ( !      
/oma*1 %\ld be cut ?r\gh1 & ! rectum1 & 
! mes5t]y & alim5t>y canal support$ by  
x1 remov$4 ,?is w expose ! urog5ital    
organs4 7,vide ,figures giv547 ,^! v>y  
greatly1 especially 9 ! females1 at     
diff]5t seasons4 ,! condition figur$    
w\ld be se5 9 late autumn1 or w9t]4 ,9  
spr+ females are (t5 f\nd copulat+ )    
males1 & !n ! ov>y itself is            
inconspicu\s1 :ile ! l[] "p ( ! oviduct 
is enorm\sly di/5d$ ) ova1 s z to be    
mi/ak5 sometimes = ! ov>y by ^? :o fail 
to note t ! ova are enclos$ by a ?9     
semi-transp>5t sk9 7wall ( oviduct74 ,! 
v5a cava inf]ior is se5 betwe5 ! kidneys
 & ! r5al portal ve9 beside ! uret]4    
,cutt+ ?r\gh ! mes5t]y support+ ! kidney
 lat]ally1 ! dorsal aorta is expos$1 &  
on ei!r side ( x ! sympa!tic *a9 & rami 
communicantes1 (t5 t+$ ) black pigm5t4  
,?is black pigm5t is a frequ5t b v>iable
 feature ( ! frog's anatomy1 & usually  
dapples or black5s ! te/es1 & also      
sometimes d>k5s ! o!rwise pale p9k      

art]ies4 ,beh9d ! kidneys ! sciatic     
plexus also becomes visible4 ,c>eful    
draw+s %\ld be made4 ,cut (f ! head ( ! 
frog1 %ave (f top ( bra9 case1 & put !  
head 9 /rong _s4  ,second ,dissection4--
 ,a fre% frog is requir$4 ,p9 out "u    
wat] z be=e1 & op5 up body cavity4 ,n[  
c>efully remove ! muscle f ! v5tral     
portion ( ! %\ld] girdle1 to expose !   
clavicles & coracoids4 ,cut away        
xiphi/]num1 & !n cut ?r\gh clavicles &  
coracoids on ei!r side1 & remove v5tral 
"p ( %\ld] girdle1 to expose ! he>t4    
,op5 out ! cut portions ( body wall &   
p94 ,! ve9s go+ t[>ds ! he>t %\ld n[1 ) 
a little exam9ation1 be evid5t4 ,make   
out ! ext]nal jugul>1 ! innom9ate1 & its
 two bran*es1 & ! pulmo-cutane\s & v5a  
cava sup]ior4 ,cle> by c>efully pick+   
away any %r$s ( semi-transp>5t tissue4  
,make out1 by feel+1 ! position ( !     
hyoid body1 & ( its ant]ior cornua4     
,note ! hypoglossal n]ve 7fir/ sp9al7   
runn+ v5tral to ?is1 & ! n9? cranial    
n]ve1 runn+ p>allel to x b dorsal to !  

hyoid-- hidd5 !re=e by ! hyoid1 &       
reappe>+ 9 front4 ,! vagus may also be  
made out less di/9ctly1 runn+           
po/]o-v5trally t[>ds ! he>t4 ,by cle>+ !
 muscle by ! rumus ( ! jaw1 ,,vii4 may  
be se51 & ! ?ird bran* ( ,v41 runn+     
across ! jaw at ab\t ! middle ( its     
l5g?4 ,pick (f ! ?9 transp>5t p]ic>dium 
f ! he>t v c>efully1 & proce$ to cut    
away all ! ve9s made out4 ,! truncus    
art]iosus may !n be foll[$ up z x       
bran*es4 ,note all ! bran*es %[n 9 !    
figures 9 ?is book4 ,! precise position 
( ! vessels w v>y to a c]ta9 ext5t ) !  
attitude 9 :i* ! frog is p9n$4 ,!       
cutane\s art]y w prev5t ! /ud5t foll[+  
up ! aortic ar* until x is cut2 !n ! ar*
 may be foll[$ r\nd until x meets its   
fell[ to =m ! dorsal aorta4 ,note !     
sympa!tic aga94 ,make c>eful draw+s (   
all ?is4 ,cut (f l[] jaw1 & note po/]ior
 n>es & ,eu/a*ian op5+s4 ,if "t all[s1  
remove ! he>t1 & exam9e by cutt+ op5 &  
wa%+4 7,comp>e1 ,section #dd7 ,remove   
eyeball1 to see ! fir/ & second bran*es 

( ! fif? n]ve1 & ! ,vidian 7i4e4        
palatial7 bran* ( ! sev5?4  ,?ird       
,dissection4-- ,read ! acc\nt ( ! frog's
 skull c>efully4 ,take ! head ( a       
rec5tly kill$ frog & drop into boil+    
wat] = a m9ute4 ,!n pick (f1 v c>efully1
 muscle1 connective tissue1 n]ves1 &    
etc41 to cle> ! cranio-facial app>atus2 
exam9e ! bones1 comp>e ) figures giv5 9 
?is book1 & draw4 ,take ! head1 :i* has 
be5 9 _s a =tnight or s1 pick away      
cranium1 & comp>e bra9 ) figures giv54  
,exam9e v5tricles1 by tak+ sections1    
aft] draw+s h be5 made4   -,! ,dog-,fi%-
  ,fir/ ,dissection4-- ,exam9e ext]nal  
*>act]s1 nasal grooves-- no int]nal     
n>es-- f9s1 spiracle1 scales pass+ ov]  
lips1 & cloaca4 ,cut (f tail bel[ !     
cloacal op5+4 ,! males are di/+ui%$ by !
 l>ge clasp]s along ! inn] edge ( !     
pelvic f94 ,op5 up body cavity4 ,usually
 ?is is 9 a t]rible mess 9 ! fi% suppli$
 by deal]s1 ?r\gh ! po/-mortem dige/ion 
( ! /oma*4 ,wa% out all ?is "u a /ream (
 wat] f a tap or wat]-bottle4 ,frequ5tly

 ! te/es are wa%$ out ( ! male 9 ?is    
op]ation & ova f ! loose ov>ies 9 !     
female4 ,n[ comp>e ) figure giv5 9 ?is  
book1 all[+ = ! collapse ( ! /oma*1 if x
 has occurr$4 ,cut ?r\gh ! oesophagus & 
rectum1 & remove alim5t>y canal f body2 
cut op5 & wa% out ! inte/9e1 & exam9e   
spiral valve4 ,n[ make a c>eful         
exam9ation ( ! cloaca & its ap]tures1 & 
dissect away ! p]itoneum hid+ ! kidney4 
,9 ! female f9d ! op5+ ( ! oviducts 9   
front ( ! liv]4 ,remove liv]1 & cut (f  
body n[ beh9d pectoral f94 ,be=e ?r[+   
tail & h9d] "p ( body away1 note !      
myotomes ( body wall1 ! noto*ord &      
v]tebral body1 neural canal1 &1 9 !     
tail1 ! haemal canal4 7,see ,section #i 
! ,dog-fi%7     ,l9es f ,fir/ ,edition  
only4    -,! relation ( ! v]tebral      
bodies to ! noto*ord may be v    well   
se5 by tak+ successive slices1 ab\t     
"o-t5? ( an in*    ?ick1 ?r\gh !        
v]tebral body4 ,! c>tilage is h>d &     
semi-transp>5t1 ! noto*ord jelly-l1 lea/
 at ! c5tres    ( ! c5tra1 & at a       

maximum int]v]tebrally4-  ,! noto*ord is
 a s(t jelly4 ,cut away ! v5tral "p ( ! 
pectoral girdle1 to op5 p]ic>dium4 ,) a 
seek]1 make out ! p]ic>dio p]itoneal    
op5+4 ,cut into ! s9us v5\s1 & run      
seek]s into ! ,cuvi]ian & hepatic       
s9uses4 ,cut op5 ! ,cuvi]ian & po/]ior  
c>d9al s9uses1 & run seek]s into _!     
afflu5ts4 ,dissect along ! truncus      
art]iosus to aff]5t bran*ials4 ,cut away
 ! he>t & oesophagus2 run a seek] up !  
dorsal aorta & cut along x f ! v5tral   
side to subclavian & eff]5t bran*ial    
art]ies4 ,sk9 ! top ( ! head4 ,note1    
:ile do+ ?is1 ! yell[1 jelly-l          
s5se-tubuli b5ea? ! sk94 ,%ave (f top ( 
bra9-case1 & leave ! head 9 _s = a week 
or s4  ,second ,dissection4-- ,place !  
head ) ! v5tral side d[nw>d1 sk9 all !  
dorsal surface z yet unsk9n$4 ,ref] to  
book = precise position ( ! ant]ior     
c>d9al s9us1 & !n cut d[n ?r\gh body    
wall into ?is j ov] gill slits4 ,! t5?  
n]ve w become visible1 ) its slit       
bran*es a?w>t ! floor ( ! s9us4 ,cle> to

 make ?is m evid5t1 & make out its      
lat]al l9e & visc]al bran*es1 & ! n9?   
n]ve4     ,l9es f ,second ,edition only4
    ,! ph>yngo-bran*ials may be felt    
b5ea? ! s9us4 ,run a    seek] f ! dorsal
 aorta to ! eff]5t bran*ials4  ,proce$  
n[ to orbit1 &1 )\t any dissection      
beyond ! removal ( sk91 make out recti &
 oblique muscles ( eyeball1 & ! optic1  
?ird & f\r? n]ves4 ,cut ?r\gh ^!        
/ructures c>efully & remove1 expos+     
n]ves sev51 & five1 z describ$ & figur$ 
9 ! text4 ,exam9e ! otic capsule by tak+
 successive slices ?r\gh x to %[ !      
labyr9? ( ! e>4 -,remove ! dorsal wall (
 ! skull to obta9 a dorsal view ( bra94 
,if ?is is suffici5tly h>d1 exam9e x2 if
 n1 return x to _s = a m conv5i5t       
occasion4- ,exam9e bra94   -,amphioxus  
,two specim5s ( ?is type %\ld be obta9$4
 ,x %\ld be exam9$ entire by ! nak$ eye 
& ) ! l[ p[] ( ! microscope4 ,imm]sion1 
9 glyc]9e w r5d] x m transp>5t2 or x may
 be cle>$ ) oil ( cloves1 put up        
tempor>ily 9 t1 or p]man5tly 9 ,canada  

balsam4 ,"o specim5 %\ld !n be p9n$ out 
9 ! dissect+ di%1 v5tral side upp]mo/1 &
 ! atrium op5$ to expose liv] & ph>ynx4 
,a "p ( ! ph>ynx may be exam9$ ) ! l[   
p[] to see ! =m ( ! gill slits4 ,!      
second specim5 %\ld be soak$ 9 turp5t9e 
= "s "t1 & !n dropp$ into melt$ p>aff9  
wax4 ,transv]se sections may !n be cut )
 a razor1 ! p>aff9 wax remov$ f ^! by   
solution 9 turp5t9e1 ! turp5t9e 9 its   
turn dissolv$ out by alcohol1 & !       
sections1 aft] imm]sion 9 oil ( cloves1 
may be transf]r$ to ,canada balsam =    
exam9ation & pres]vation4 ,?is "w %\ld n
 be attempt$ until "s practical         
hi/ological "w has be5 done 9 botany1 & 
x may be altoge!r avoid$ by ! pur*ase ( 
/a9$ & m\nt$ sections4   -,developm5t   
,laboratory "w 9 ?is portion ( ! sci5ce 
is n usually und]tak5 by elem5t>y /ud5ts
 ( biology1 b ! read] w probably f9d x  
helpful1 9 ! realization ( ! facts giv5 
9 ?is book1 to look out = frog spawn1 9 
,febru>y & ,m>*1 & to cat* & exam9e     
tadpoles ( v>i\s sizes4 ,a small        

dissect+ di% may be made by p\r+ melt$  
p>aff9 wax into "o ( ^? %all[ *9a pots  
*emi/s use = cold-cream1 & tadpoles may 
be p9n$ out ) entemologi/s' p9s &       
dissect$ ) ne$les4 ,b ?is is a "w (     
sup]]ogation4 ,p>tially incubat$ h5's   
eggs may be obta9$ at a small co/ almo/ 
any:]e1 & ! lat] /ages pr(itably exam9$ 
& dissect$ "u w>m wat]4 ,= a cle>       
und]/&+ ( ! allantois & amnion1 ?is la/ 
is almo/ indisp5sable4 ,a few           
microscopic slides ( sections (         
embryonic *icks %\ld also be comp>$ )   
our r\gh diagrams4     -,key =          
,dissection ,%eets1 & ,abbreviations4   
,%eet #a  ,figure #a4 ,ma9 facts ( !    
,rabbit's ,anatomy 7diagrammatic74 an41 
anus4 a4ao41 ar* ( ! aorta4 au41        
auricle4 a4r41 ad-r5al body4 br41 bra94 
b4d41 bile duct4 br*41 bron*us4 cd4/41  
c>diac end ( /oma*4 co41 colon4 cae41   
caecum4 ddnm41 duod5um4 d4ao41 dorsal   
aorta4 dia41 diaphragm4 ep41 epiglottis4
 g4d41 g5ital duct 7ei!r sex74 il41     
ileum4 94art41 innom9ate art]y4 k41     

kidney4 lg41 lung4 lv41 liv]4 l41 l>ynx4
 l4s4c41 l4c4c4 left common c>otid      
art]y4 m41 m\?4 na41 nasal passage4     
oes41 oesophagus4 p4v41 pyloric valve4  
p4d41 pancreatic duct4 pt41 p]itoneal   
cavity4 r41 rectum4 /41 /oma*4 /m41     
/]num4 s4r41 sacculus rotundus4 s4c41   
sp9al cord4 tr41 tra*ea4 ur41 uret]4    
ur4b41 ur9>y bladd]4 v4b41 a v]tebral   
body4 v4ap41 v]mi=m app5dix4 v4v41 v4p4 
velum palatium4 v41 v5tricle ( he>t4    
v4c4i41 v5a cava inf]ior4  ,figure #b4  
,! ,liv] 7diagrammatic74 g4b41 ! gall   
bladd]4 r4l41 r4c41 l4l441 l4c41 "r     
lat]al & c5tral1 & left lat]al & c5tral1
 lobes respectively4 sp41 ! ,spigelian  
lobe 7fits into angle ( /oma* &         
oesophagus74  ,illu/ration3 ,diagram    
,%eet #a4     ,%eet #b  ,figure #a4 ,!  
,rabbit's ,circulation 7see footnote to 
,section #de74  7,?r\gh\t l4 indicates  
left1 r4 "r4 ,vessels )\t r4 or l4      
prefix$ are m$ian47  -99 ,! figure is   
inaccurate at "o po9t2 l4c4c4 %\ld spr+ 
f ! base ( inn4 ,see ,%eet #i4- ,fir/   

,edition only text  ao4a41 aortic ar*4  
au41 auricle4 az4v41 7p4c4 9 ,figure    
#b71 azygos ve94 c4c41 common c>otid4   
c4il4a41 common iliac art]y4 coe4a41    
coeliac art]y4 d4ao41 dorsal aorta4     
e4il4v41 ext]nal iliac ve94 e4ju41      
ext]nal jugul> ve94 f41 femoral art]y4  
h4v41 hepatic ve94 inn41 innom9ate      
art]y4 94j41 int]nal jugul> ve94        
i4il4a41 int]nal iliac art]y4 i4il4v41  
int]nal iliac ve94 k41 kidney4 lv41     
liv]4 l4g4v41 li5oga/ric ve9 7portal74  
m4v41 mes5t]ic 7portal sy/em74 p4m4a41  
po/]ior mes5t]ic art]y4 p4v41 ma9 portal
 ve94 p4a4 pulmon>y art]y4 r41 rectum4  
r4a41 r5al art]y4 r4v41 r5al ve94 s4v41 
& a41 sp]matic 7or ov>ian7 ve9 & art]y  
7to g5ital organ74 s4mes4a41 sup]ior    
mes5t]ic art]y4 s4-cl4a41 subclavian    
art]y4 s4-cl4v41 subclavian ve94 v4c4s41
 v5a cava sup]ior4 v4c4i41 v5a cava     
inf]ior4 v4 or vn41 v5tricle4  ,figure  
#b4 ,figure ( ,circulation 7simplifi$7  
illu/rat+ c]ta9 po9ts 9 developm5t to be
 ref]r$ to lat]4  ,figure #c4           

,respiration4 ,see text1 ,section #da4  
,figure #d4 ,blood4 ,see text1 ,section 
#ce4  ,illu/ration3 ,diagram ,%eet #b4  
,%eet #c  ,hi/ological ,figures1 #a4    
,no numb]s ,i41 or ,,ii4  ,figure ,,iii4
 ,an amoeba4-- n41 nucleus4 ns41        
necleolus4 c4v41 contractile vacuole4   
,figure ,,iv4 ,embryonic tissue f !     
bla/od]m ( a *ick4  ,figure ,v4 ,column>
 epi!lium4-- g4c4#a1 g4c4#b1 g4c4#c1    
successive phases 9 ! developm5t ( a    
goblet cell4  ,figure ,,vi4 g4end41 is  
gem9at+ endo!lium2 ! cells divide &     
app>5tly drop (f to become :ite         
corpuscles 9 ! lymph curr5t4 sq4end41   
squam\s endo!lium f ! mes5t]y4 sq4ep41  
squam\s epi!lium 7f ! muc\s membrane )9 
! *eek74 /41 are op5+ 7/omata7          
communicat+ betwe5 ! lymphatics 9 !     
mes5t]y & ! p]itoneal 7coelomic7 space4 
,figure ,,vii4 ,ciliat$ epi!lium f ! ro(
 ( ! frog's m\?4  ,figure ,,viii4 ,=ms (
 gl&s4-- g4ep41 is a ga/ric gl& f !     
/oma*2 trs41 bel[1 is cross section4    
,?is is "o ( ! simple/ types ( gl&4     

s4g41 a sweat gl&1 is also a simple     
tube1 b convolut$ bel[4 r4g41 is a      
racemose gl&1 su* z ! pancreas1         
,brunn]'s or ! saliv>y gl&s4  ,! kidney1
 we %all see lat]1 is simply an         
aggregate ( bran*+ tubuli 7,%eet #g74   
,figure ,,ix4 ,a duod5al villus4-- lac41
 ! lacteal4 v41 ! ve94  ,figure ,x4a4   
,diagram ( liv] /ructure4-- b4d41 !     
int]-lobul> bile duct4 h4a41 ! hepatic  
art]y1 br++ blood to oxyg5ate & n\ri% ! 
liv] tissue1 & simil>ly di/ribut$4 h4v41
 ! hepatic ve9 tak+ blood f ! liv] to ! 
he>t1 its twigs comm5c+ 9 ! lobuli      
7intra-lobul>74 lb4 lb41 lobuli4 p4v41 !
 portal ve9 br++ blood1 f :i* sub/ances 
are to be elaborat$1 into ! liv]1 &     
break+ up betwe5 ! lobuli 7int]-lobul>74
  ,figure ,x4b4 ,a diagram ( ! appe>ance
 ( an inject$ liv] lobule z se5 9       
section "u ! microscope4  ,illu/ration3 
,diagram ,%eet #c4     ,%eet #d         
,hi/ological ,diagrams1 #b4  ,figure    
,,xi4 ,a blood capill>y4 ,:ite          
corpuscles are migrat+ ?r\gh ! walls    

into ! tissues 7comp>e ,section #ff74   
,figure ,,xii4 ,hyal9e c>tilage         
7,section #fd74  ,figure ,,xiii4 c4c41  
connective tissue corpuscle4 w4i4f41    
:ite inela/ic fibres4 y4e4f41 yell[     
ela/ic fibres4   ,figure ,,xiv4         
,botryoidal tissue 7,section #ff74      
,figure ,,xv4 ,developm5t ( a fat       
drop4-- f4d41 fat drop1 9 a connective  
tissue corpuscle2 c4c41 9 ! =mation (   
adipose tissue 7,section #fg74  ,figure 
,,xvi4 ,diagrammic cross section ( a    
long bone4-- b4c41 bone corpuscle 9 a   
lacuna4 ,h4v41 ,hav]sian vessel 79 !    
,hav]sian canal7 surr\nd$ by conc5tric  
lamellae ( bone1 c4l41 & toge!r ) ^! &  
zones ( bone corpuscles1 call$ a        
,hav]sian sy/em4 i4l41 inn] lamellae4   
m4c41 m$ull>y canal full ( yell[ m>r[4  
o4l41 out] lamellae4 p4o41 p]io/eum4    
,figure ,,xvii4 ,to illu/rate bone      
developm5t 7,section #ga74  ,figure     
,,xviii4 ,d5tition ( rabbit1 incisors   
#b_/a1 can9e #j_/j1 premol> #c_/b1 mol> 
#c_/c4  ,illu/ration3 ,diagram ,%eet #d4

     ,%eet #e4  ,diagram ( ! ,rabbit's  
,bones4 ,to be comp>$ ) ! real ?+s4  ,d 
& ,d' %[ ! =e & h9d limbs1 to illu/rate 
_! homology4 ,d is 9 ! embryonic        
position4 ,! radius & tibia are1 at an  
e>ly /age 9 developm5t1 on ! ant]ior    
edge ( _! respective limbs2 ! ulna &    
fibula1 po/]ior2 ! =m] are spok5 ( z    
preaxial 9 position1 ! latt] z po/axial4
 ,b 9 ! adult ! hum]us is twi/$ s t !   
proximal end ( ! radius lies at ! out]  
side ( ! elb[1 :5ce x crosses ! ulna1 s 
t its di/al end is inside1 :ile ! femur 
is also twi/$ r\nd1 s t ! entire tibia  
is int]nal4  ,figures #a & #b4          
-,limbs4-- a4c41 acetabulum4 acr41      
acromion4 z41 a/ragulus4 c41 c>pus4 ca41
 calcaneum4 co41 coracoid4 coty41       
cotyloid bone4 fb41 fibula4 fe41 femur4 
g41 gl5oid cavity 7= head ( hum]us74    
hd41 head ( femur4 hum41 hum]us4 i41    
ilium4 is41 is*ium4 m4c41 meta-c>pals4  
na41 navicul>4 o41 olecranon process (  
ulna4 o4f41 olfactory fossa4 pb41 pubis4
 r41 radius4 u41 ulna4  ,figure #c4     

-,/]num4-- ,mb41 manubrium4 r#a41 r#b41 
& etc41 /]nal ribs4 /41 /]nebrae4 xi41  
,xiphi/]num4  ,figure #d4 ,v]tebrae4--  
,at41 ,atlas4 ,ax41 axis4 c41 b4 c5trum4
 ,c4,v41 caudal v]tebra4 c4v41 ,c]4,v4  
c]vical v]tebra4 ep41 epiphysis4 f4r41  
fus$ rib 79 c]vical v]tebrae74 ,l4,v41  
,lumb> v]tebra4 m41 metapophysis 7(     
lumb> v]tebra74 n4a41 neural ar*4 n4s41 
neural sp9e4 r41 rib4 ,s4,v41 sacral    
v]tebra4 ,t4,v41 ,?oracic4 tr4p41       
transv]se process4 v4a4c41 v]tebr>t]ial 
canal4 z41 zygapophysis4  ,illu/ration3 
,diagram ,%eet #e4     ,%eet #f4  ,!    
,skull ( ,canis499-- #a4 ,dorsal4 #b4   
,v5tral4 #c4 ,"r ,lat]al ,aspect4 #d4   
,section a little to ! left ( ! nasal   
septum4 #e4 ,l[] jaw 7small]7 #f4 ,hyoid
 app>atus4  ,l9es f ,fir/ ,edition only4
 -99,a ,fox 9 ?is case4 ,! skull is q l 
t ( a ,dog1 b x has ! advantage ( m     
di/9ct sutures betwe5 ! bones4-  a4n41  
ant]ior n>es4 a4s41 ali-sph5oid4 b4h41  
body ( ! hyoid4 b4o41 basi-occipital4   
b4sp41 basi-sph5oid4 c41 condyle ( !    

skull4 c4#a1 c4#d1 can9es4 c4f41 condyl>
 =am5 7= ,,xii474 c4h41 c]ato-hyal4     
,e4f41 ,eu/a*ian =am54 e4h41 epihal4    
-e4n41 or a4n41 ! ant]ior n>es4- e4o41  
exoccipital4 e?41 e?moid4 e4t41         
e?mo-turb9al4 f41 frontal4 f4l4a41 =am5 
lac]um ant]ius4 f4l4m41 =am5 lac]um     
m$ium4 f4l4p41 =am5 lac]um po/]ius 7=   
,,ix41 ,x41 ,,xi474 ,f4,m41 or f4m41    
=am5 magnum4 f4o41 =am5 ovale4 f4r41    
=am5 rotundum4 i41 incisors4 ju41 jugal4
 m41 mol>s4 m4t41 maxillo-turb9al4 mx41 
maxilla4 na41 nasal4 n4t41 nasal        
turb9al4 o4f41 optic =am54 o4s41        
orbito-sph5oid4 p41 or pal41 palat9e4   
pa41 p>ietal4 p4m41 pre-maxilla4 p4m4#a1
 p4m4#d1 premol>s4 p4n41 po/]ior n>es4  
p4sp41 pre-sph5oid4 pt41 pt]ygoid4 s4h41
 /ylo-hyal4 s4m4f41 /ylo-ma/oid =am5 7= 
,,vii474 s4o41 supra-occipital4 sq41    
squamosal4 s4t41 sectorial too?4 t4h4   
?yro-hyal4 vo41 -black l9e indicat+     
position (- vom]4 z4p41 zygomatic       
process ( squamosal4  ,illu/ration3     
,diagram ,%eet #f4     ,%eet #g  ,figure

 #a4 ,/riat$ muscle fibre 7( ! ,rabbit71
 ruptur$ to %[ s>colemma4 e4p41 its end 
plate4 ,k4m41 membrane ( ,krause4 n41   
nucleus4 nv41 n]ve4 sc41 s>colemma4     
s4e41 s>c\s elem5ts4  ,figure #b4       
,c>diac muscle4  ,figure #c4 ,un/riat$  
muscle fibres4  ,figure #d4 ,diagram ( !
 ,sk94 b4v41 blood vessel4 d41 areol>   
tissue ( ! d]mis 7mesobla/ic74 s4c41    
/ratum corneum1 & s4m41 /ratum mucosum (
 ! epid]mis4 s4g41 sweat gl&4 t4c41     
tactile corpuscle4  ,figure #e4 ,to     
illu/rate ,kidney /ructure4-- a4b4v41 & 
e4b4v41 aff]5t & eff]5t blood-vessels1 (
 :i* ! latt] g to break up ^u ! tubli4  
,b4c41 "o ( ,b[man's capsules ( !       
cortex2 ur4t41 ! ur9if]\s tubule runn+ f
 x into ! m$ulla1 :]e x loops & bran*es2
 ar\nd x bran*es a blood-vessel1 ( :i* !
 latt] g to break up ^u ! tubuli4 c41   
cortex4 g41 glom]ulus1 a knot (         
blood-vessels 9 ! capsule4 m41 m$ulla4  
p41 pelvis4 ur41 uret]4  ,! wat] ( !    
ur9e is probably filt]$ (f 9 ! capsule1 
! urea & o!r salts secret$ by ! tubuli4 

,no ,figure #f4  ,figure #g4 ,!         
,auditory /ructures ( ! ,rabbit         
7diagram74 ,see text1 ,section #aae4    
,figure #h4 ,! ,eye 7diagram74 ,see     
text1 ,section #aaa4  ,figure #i4 ,!    
,ret9a 7diagram74 ,see text1 ,section   
#aab4  ,illu/ration3 ,diagram ,%eet #g4 
,%eet #h  ,! ,bra9 ( ! ,rabbit4--  #a4  
,9 m$ian section4 #b4 ,f above1 ) ! top 
( ! "r hemisph]e slic$ (f horizontally  
at ! level ( ! corpus callosum4 #c4 ,a  
deep] section ?r\gh ! ?alam5cephalon1   
correspond+ to ,b 9 7#a74 #d4 ,"u-view (
 ! bra94 #e4 ,diagram ref]r$ to 9 ! text
 & = comp>ison ) ,%eet #g1 #c;b41 &     
,%eet #ah1 #b4  ,figures #a-e4 ar41 arr[
 9 ! it]4 a4c41 ! ant]ior commissure1 a 
?ick5+ ( ! ant]ior wall ( ! ?ird        
v5tricle4 c4c41 corpus callosum4 c4 cb41
 crura c]ebri4 c4h41 c]ebral hemisph]es4
 c4q41 corpora quadrigem9a4 f4cbm4 7"r71
 flocculus ( ! c]ebellum4 l4h41 left    
c]ebral hemisph]e 7*474 l4l41 lat]al    
lobe ( c]ebellum4 m4c41 middle          
commissure4 m4o41 m$ulla oblongata4 op41

 optic n]ve4 o4l41 olfactory lobe4 o4?41
 7"r71 optic ?alamus4 p4c41 po/]ior     
commissure 7?ick5+ ( po/]o-dorsal wall (
 ! ?ird v5tricle74 p4g41 p9eal gl&4 pt41
 pituit>y body4 p4,v41 pons ,v>olii4    
s4c41 ?9 ro( ( ! f\r? v5tricle4 v4cbm41 
v]mis ( c]ebrum4 v4l41 lat]al v5tricle4 
,figure #d4 ,n]ves4-- ,i41 ,olfactory4  
,,ii41 ,optic4 ,,iii41 ,oculo-motor4    
,,iv41 ,pa!ticus4 ,v41 ,trigem9al4      
,,vi41 ,abduc5s4 ,,vii41 ,facial 7portio
 dura74 ,,viii41 ,auditory 7portio      
mollis74 ,,ix41 ,gu/atory               
7glossoph>yngeal4 ,x41 ,pneumoga/ric or 
vagus4 ,,xi41 ,sp9al ,accessory4 ,,xii41
 ,hygoglossal4  ,figure #f4 ,! ,sp9al   
,cord 9 section4-- c4c41 ! c5tral canal4
 d4f41 ! dorsal fissure4 d4n41 ! dorsal 
n]ve root2 g41 its ganglion4 v4f41 !    
v5tral fissure4 v4n41 ! v5tral n]ve     
root4  ,note t 9 ,figure #a ! c5tral    
canal is cont9u\s ) ! f\r? v5tricle4    
,figure #g4 ,hi/ological elem5ts4--     
g4c41 multipol> ganglion cell4 n41      
nucleus ( a m$ullat$ n]ve4 a4c41 its    

axis fibre4 s4,s41 7%ea? ( ,s*wann71    
m$ull>y %ea? int]rupt$ at int]vals by   
n4,r41 ! nodes ( ,ranvi]4 n4m4f41 a     
non-m$ullat$ fibre4  ,illu/ration3      
,diagram ,%eet #h4     ,%eet #i4  -,!   
,n]ves ( ! ,rabbit4  ,figure ,i4 ,r\gh  
sket* ( dissection ( ! neck f ! left    
v5tral aspect4-- ,! b&s ( muscle betwe5 
hyoid1 m&ible1 & /]num1 & ! ?ymus gl&   
c>efully cle>$4 lr41 is ! l>ynx1 & b41 !
 balla4 s4m4g41 ! "r sub-maxill>y gl& 7!
 left has be5 remov$74  ,! n]ves are    
numb]$4  l4r4l4n41 r4r4l4n4 is ! left   
recurr5t l>yngeal loop+ "u t solid      
connection betwe5 ! pulmon>y art]y      
7p4a47 & ao41 ! aortic ar*1 :i* 0 an op5
 tube 9 ! embryo1 ! ductus art]iosus4   
hy41 is ! hyoid ) its po/]ior cornua4   
ph4n41 is ! phr5ic n]ve4 r4r4l4n41      
l4r4l4n4 is ! "r recurr5t loop+ "u !    
sub-clavian4 s4c4g41 is ! sup] or       
c]vical ganglion ( ! sympa!tic 7sym472  
s4l4n41 is ! left sup]ior l>yngeal1 & g4
 ! left depressor bran* ( x4 z41 is !   
ramus desc5d5s noni ( ! twelf? n]ve4  ,9

 e>ly developm5t ! he>t lay j b5ea? !   
ph>ynx 9 ! position ( ! l>ynx 7comp>e   
,dog-fi% & ,frog72 z ! neck elongat$1 ! 
he>t %ift$ back ) its vessels1 & s !    
long loop ( ! recurr5t l>yngeal comes to
 be drawn out 9 ?is s+ul> way4  ,figure 
,,ii4 ,diagram ( orbit to %[ ,v4#a      
orbit-nasal1 ,v4#b ! maxill>y1 & ,v4#c !
 m&ibul> bran* ( ,v4 ,9 ord] to %[ ^! 9 
dissection1 ! mal> mu/ be cut away1 & ! 
eye & gl&s ( ! orbit remov$4 s4r41 e4r4 
p4r41 i4r41 & a4r41 cut ends ( !        
sup]ior1 ext]nal 7or po/]ior71 inf]ior1 
& ant]ior 7or int]nal7 recti muscles4   
s4o41 & i4o41 ! sup]ior & inf]ior       
obliques4  ,figure ,,iii4 ,g5]al diagram
 ( ! ,rabbit's cranial n]ves4  ,figure  
,,iv4 ,r\gh sket* ( dissection ( ! n]ves
 & blood-vessels dorsal to /oma*4--  ,! 
/oma* turn$ ov] to ! animal's "r1 !     
,spigelian liv] lobe cle>$ f !          
oesophagus1 ! mes5t]y support+ sple5 &  
hid+ sol> plexus pick$ (f1 & ! mes5t]y  
hid+ sympa!tic cle>$4  coe4art41 coeliac
 art]y1 & s4m4a41 sup]ior mes5t]ic      

art]y4 coe4g4 coeliac1 & s4m4g41 sup]ior
 mes5t]ic ganglion4 ,! two toge!r =m !  
sol> plexus4 l4abd4sym41 left abdom9al  
sympa!tic 79 ! actual dissection1 ! "r  
w\ld also be visible74 l4a4r41 left     
adr5al4 l4sp4n41 left splan*nic n]ve4   
r4art41 r5al art]y4 r4v41 r5al ve94 /41 
! /oma*1 & sp41 ! sple54 x41 ! vagus on 
oes41 ! oesophagus4  ,illu/ration3      
,diagram ,%eet #i4     ,%eet #aj4       
-,reproductive ,organs ( ! ,rabbit4     
,figure #a4 ,! ,male4  ,figure #b4 ,!   
,female ,organs4 7,! symbols bel[ !     
figures indicate ! sex47  pb41 is !     
pubic symphysis :i* has be5 cut ?r\gh4  
,r41 ! rectum1 ) r4g41 ! rectal gl&1 &  
a41 ! anus4 t41 ! tail4 r4ur41 ! "r     
uret]4 l4ur41 ! left uret]4 ur4b41 !    
ur9>y bladd]4  ,9 ! ,male ep41 !        
epididymis4 ,p41 ! p5is4 pp41 ! prepuce4
 scr41 ! scrotal sac1 conta9+ ^!2       
r4v4d41 ! "r vas def]5s4 ,t41 is !      
te/is4 u4m41 ! ut]us mascul9us4  ,9 !   
,female c4ut1 ! left cornu ut]i4 ,f4t41 
! left ,fallopian tube4 ov41 is ! ov>y1 

) a ,graafian follicle1 ,g4,f4 ,v41 !   
vag9a4 v4b41 ! ve/ibule4  ,figure #c4   
,diagram ( ov>y ) /ages 9 ! developm5t (
 a ,graafian follicle #a1 #b1 #c1 #d1   
#e1 see text1 ,section #acg4 ,! arr[    
indicates ! *anges 9 position ( !       
develop+ follicles4  ,illu/ration3      
,diagram ,%eet #aj4     ,%eet #aa4      
,figure #a4 ,g5]al dissection ( ,frog   
7male74  ,figure #b4 ,! he>t & great    
vessels laid op54  ,figure #c4 ,!       
circulatory sy/em f ! side4  ,figure #d4
 ,blood4 n41 nucleus4 r4c41 r$ corpuscle
 7oval & nucleat$74 w4c41 :ite corpuscle
  ,small figure ( ,frog 9 left-h& corn] 
is to %[ position ( heel1 h4  ,ref]5ce  
,lett]s4 all4b41 allantoic bladd] 7     
ur9>y bladd]74 c4ad41 corpus adiposum4  
cl4c41 cut end ( ! "r clavicle4 d41     
duod5um4 g4b41 gall bladd]4 il41 ileum4 
k41 kidney4 l4au41 left auricle4 l4g41  
lung4 l4int41 l>ge inte/9e4 l4s4v41     
longitud9o-spiral valve4 ,l4v41 ,liv41  
liv]4 pan41 pancreas4 r4au41 "r auricle4
 sp41 sple54 /41 /oma*4 ,t41 te/is4     

t4a41 truncus art]iosus4 ur41 urog5ital 
duct4 v41 v5tricle ( he>t4  ,art]ies    
7:ite74 ao41 aorta4 c4a41 c>otid ar*4   
c4g4 c4gl41 c>otid gl&4 coe41 coeliac4  
cu41 -& pa41- cutane\s4 d4ao41 dorsal   
aorta4 e4c41 l+ual art]y4 i4c41 int]nal 
c>otid4 l4a4a41 left aortic ar*4 pa41 & 
p41 pulmon>y4 p4c4 p4cu41               
pulmo-cutane\s4 r4a4a41 "r aortic ar*4  
s4cl41 sub-clavian4 t4a41 truncus       
art]iosus4  ,ve9s ( ! ,caval ,sy/em     
-7black7-4 b4v41 bra*ial 7f =e limb74   
e4j41 ext]nal jugul>4 h4v41 hepatic ve94
 i4j41 int]nal jugul>4 94v41 innom9ate  
ve94 l4v4c4s41 left v5a cava sup]ior4   
p4v41 cutane\s ve94 s4cl4v41 sub-clavian
 ve9 s4s4r41 sub-scapul> ve94 v4c4i41   
v5a cava inf]ior4  ,ve9s ( ! ,portal &  
,r5al ,portal ,sy/ems -7%ad$7-4 a4ad41 &
 a4ab4v41 ant]ior abdom9al ve94 b4v41 & 
p4v41 unit$ are call$ ! sub-clavian ve94
 l4fm41 left femoral4 l4p41 left pelvic4
 l4r4p41 7& r4p47 left r5al portal4     
l4sc41 left sciatic4 p4v41 portal ve94  
-7,! ant]ior abdom9al is col\r$ black 9 

,figure #a47-  ,! cutane\s art]y 9 !    
above figures is turn$ back4 ,9         
dissection x w be f\nd to lie ov] & hide
 ! dorsal-w>d sweep ( ! aortic ar*4     
,illu/ration3 ,diagram ,%eet #aa4       
,%eet #ab4  ,figure #a4 ,upp] view ( !  
,frog's bra94  ,figure #b4 ,"u view ( ! 
same4  ,figure #c4 ,! same-- m$ian      
section4  ,figure #d4 ,! di/ribution ( !
 ,frog's n]ves4 ,comp>e ,%eet #i1       
,figure ,,iii4  ,! %ad$ "p 9 #d is !    
-otic capsule- tympanum4 ,! hyoid       
app>atus is r\ghly repres5t$ 9 black to 
%[ its relation to ,,ix4 7dorsal to x7 &
 sp4 #a 7v5tral74 ,comp>e n]ves ,,ix &  
,,xii 9 ,%eet #i4 ,! n]ves are numb]$4  
cb41 ! c]ebellum4 c4h41 c]ebral         
hemisph]es4 f4t41 filum t]m9ale4 g4tr41 
ganglion on ! fif? n]ve4 l4t41 lam9a    
t]m9alis4 mb41 mid-bra94 md41 m$ulla    
oblongata4 o4l41 optic lobes4 p941 p9eal
 gl&4 pit41 pituit>y body4 r4h41        
olfactory lobes 7rh95cephalon74 ?4c41   
?alam5cephalon4 sp4#a1 fir/ sp9al n]ve4 
sp4#b1 #c1 bra*ial plexus to =e limb4   

,figure #e4 ,! sp9al column 7& pelvic   
girdle7 ( ! ,frog4  ,figure #e;b4       
,v]tebrae4  ,figure #f4 ,! pectoral     
girdle & limb1 dorsal view4  ,figure #g4
 ,! pelvic girdle & "r limb f ! side4   
7l4h4 %[s ! position ( ! "r lymph       
he>ts-- !y are pair$47  z41 a/ragalus4  
b41 body4 c41 calc> 78 a six? digit74   
cal41 calcaneum4 cl41 clavicle ov]ly+ a 
procoracoid c>tilage4 co41 coracoid4 f41
 fibula4 ,,fe41 femur4 h41 hum]us4 il41 
ilium4 is41 is*ium4 o4/41 omo/]num4 pu41
 pubis4 r41 radius4 sc41 scapula4 s4sc41
 supra-scapula4 s4v41 sacral v]tebra4   
t41 tibia4 t4p41 transv]se process4 ul41
 ulna4 ur41 uro/yle4 x41 xiphi/]num4 z41
 zygapophysis4  #a1 #b1 & etc41 fir/1   
second1 & etc41 digits4  ,d4 & ,d'4 are 
simplifi$ diagrams ( ! limbs = comp>ison
 ) ! simil> ones ( ! ,rabbit4 ,9 ea*    
girdle we h a dorsal ossification       
7scapula1 ilium7 & two v5tral p>ts      
7pubis & procoracoid c>tilage1 is*ium & 
coracoid71 & at ! meet+-place ( ! ?ree 9
 ea* case ! proximal bone ( ! limb      

7hum]us1 femur7 articulates4            
,illu/ration3 ,diagram ,%eet #ab4       
,%eet #ac4  -,urog5ital ,organs ( !     
,frog4  ,figure #a4 ,! ,male4  ,figure  
#b4 ,! ,female4 ,! oviduct remov$ on !  
animal's left1 & ! ov>y on its "r4      
,organs common to bo? sexes4-- al4b41   
allantoic bladd]4 c4ad41 corpus         
adiposum4 cl41 cloaca4 int41 inte/9e4   
,k41 kidney4 lg41 7dott$ outl9e (7 lung4
 oes41 oesophagus4 r4p4v41 r5al portal  
ve94 /41 /oma*4  ,9 ! ,male4-- ,t41     
te/is4 v4e41 vasa eff]5tia4 u4g4d41     
urog5ital duct4 p41 pro/ate gl&4  ,9 !  
,female4-- adr41 adr5al4 f4t41 fallopian
 tube 7ant]ior "p ( oviduct74 99 its    
op5+4 o4d41 oviduct 7lett]s on ! op5+   
-ut]9e portion-74 ov41 ov>y4 ur41 uret]4
  7,?is w\ld be ! condition ab\t        
midw9t]47 ,9 ,m>* o4d4 w be ei!r        
enorm\sly di/5d$ ) eggs1 or l>ge1       
flabby1 & empty1 & ov4 w be small &     
br[ni%1 )\t any l>ge eggs2 ! ov>y       
gradually recov]s its size ?r\gh !      
summ]4  ,figure #c4 ,sp]matozoa atta*$  

to ! p>5t cell 7g4e47 f ! l9+ epi!lium (
 ! te/is1 & "o free4 fl41 ! flagellum4  
,illu/ration3 ,diagram ,%eet #ac4       
,%eet #ad  -,skull ,/ructure &          
,developm5t ( ! ,frog4  ,figure #a4 ,i41
 ,,ii41 e>ly & late /ages ( ! ,tadpole's
 *9drocranium4 ,diagrammatic4  ,figure  
#b4 ,dorsal view ( a "y ,frog's         
cranium-- ! membrane bones remov$4      
,diagrammatic4  ,figures #c & #d4       
,dorsal & v5tral views1 respectively1 ( 
! ,frog's skull-- ! l[] jaw remov$4     
,figure #e4 ,side view ( ! ,frog's      
skull4  ,figure #f4 ,m$ian section ( !  
bra9 case4  ,figure #g4 ,! hyoid        
app>atus4  ,figure #h4 ,i41 ,,ii41      
,,iii41 progressive /ages ( ! ,tadpole's
 skull f ! side4 ,aft] ,w4 ,k4 ,p>k]4   
,figure #i4 ,f41 side & h9d views ( !   
,frog's skull4 ,d41 ! same ( ! ,dog4    
,r\ghly diagrammatic4  ,n4,b4-- ,9 all  
c>tilage is dott$1 c>tilage bone        
cross-b>r$1 & membrane bone1 :ite4 ,9   
,figure #d1 pt41 %\ld be cross-b>r$2 & 9
 #e1 ?4h4 pla94  a4c41 ant]ior cornu (  

hyoid 7 ,,*47 -n lett]$1 9 ,figure #e-4 
a4o41 antorbital c>tilage4 ar41         
angulo-spl5ial -7,on ,frog ,section #cd1
 = ,articul>e read -,angulo-,spl5ial7-4 
-b41 p>a*ordal "p ( bra9 box-4 b4c41    
bra9 case4 b4h41 body ( hyoid4 b4r41    
bran*ial ar*es4 ,,*  a4c4 c4t41 cornua  
trabeculi4 d41 d5t>y4 e41 eye4 ,e4,n41  
ext]nal n>es4 e4o41 exoccipital bone4   
f41 f5e/ra 7membran\s "p ( cranial      
wall74 -f4p41 fronto-p>ietal4- h4m41    
hyom&ibul> cleft  ,eu/a*ian tube & e>   
drum4 mb41 m&ible4 ,m4,c41 ,meckel's    
,c>tilage4 m4mk41 m5to-,meckelian bone4 
m4p41 m\? passage4 mx41 maxilla4 n4c41  
noto*ord4 n4o41 nasal organ4 n4p41 nasal
 passage4 ot41 or o4c41 otic 7auditory7 
capsule4 pal41 palat9e bone4 ,,pal41 h>d
 palate ( ,mammal4 p4c41 p>a*ordal4     
p4f41 p>ieto-frontal -see f4p4- p4m41   
premaxilla4 ,p4,n41 int]nal n>es4 p4o41 
prootic bone4 p4p41 palato-pt]ygoid     
c>tilage4 psph41 p>asph5oid bone4 pt41  
pt]ygoid bone4 q41 quadrate c>tilage4   
q4j41 quadrato-jugal4 s4e41 sph5e?moid  

bone4 sq41 squamosal4 t41 trabecul> "p (
 bra9 box4 t4c41 trabecula4 ?4h41       
?yrohyal4  ,illu/ration3 ,diagram ,%eet 
#ad4     ,%eet #ae  ,figure #a4         
,dissection ( -,male- ,female ,dog-,fi% 
to %[ alim5t>y canal1 ! p]ic>dium also  
be+ op5$ & ! cloaca slit up4 ,above is  
also se5 ! dorsal view ( ! head4        
,figure #b4 ,! pelvic girdle & f9       
skeleton ( a male4  ,no ,figure #c1 9   
,fir/ ,edition4  ,figure #d4 ,! spiral  
valve 9 ! colon4 ,figure #c1 9 ,second  
,edition4  a4p41 abdom9al pore4 aur41   
-auricle- atrium ( he>t4 b4d41 bile     
duct4 b4pt41 basi-pt]ygium4 -cl41       
clasp]4- cl4c41 -its- ! support+        
c>tilage ( ! clasp]4 co41 colon4 d'dnm41
 duod5um4 e41 ! eye4 g4bl41 gall bladd]4
 g4s41 gill slits4 ,l4,lv41 left lobe ( 
liv]4 ,m4,lv41 middle lobe ( liv]4 olf41
 olfactory op5+4 pan41 pancreas4 pcd41  
p]ic>dial wall4 pel4g41 ! pelvic girdle4
 p4p41 arr[ ?r\gh p]ic>dio-p]itoneal    
canal4 r4g41 rectal gl&4 ,r4,liv41 "r   
lobe4 sp41 spiracle4 spl41 sple54 /41 ! 

/oma*4 s4v41 s9us v5osus4 u4g4p41       
uro-g5ital pore4 v41 v5tricle4          
,illu/ration3 ,diagram ,%eet #ae4       
,%eet #af4 ,figure #a4 ,circulation ( ! 
,dog-,fi%4  ,figure #b4 ,simplifi$ & m  
typical fi% circulation1 9 :i* ! po/]ior
 c>d9als h n coalesc$ 9 ! m$ian l9e4 ,! 
,cuvi]ian ve9s  ! v5a cava sup]ior ( !  
high] type2 ! po/]ior c>d9al is         
repres5t$ by ! azygos ve9 9 ! ,rabbit4  
,comp>e ,%eet #bd1 ,figure #g1 & ,%eet  
#b1 ,figure #b4  ,figure #c4 ,side view 
( ! p]ic>dium4  a4br41 aff]5t bran*ial  
art]y4 a4c4s41 ant]ior c>d9al s9us 7    
int]nal jugul> ve974 au41 atrium        
7auricle7 7 ! two auricles ( high] =ms74
 b4a41 bulbus art]iosus4 c4a41 conus    
art]i\s4 cd4 a41 caudal art]y4 cd4v41   
caudal ve94 c4s41 ,cuvi]ian s9us4 d4a41 
dorsal aorta4 ,e41 eye4 e4br41 eff]5t   
bran*ial art]ies4 g4s41 9 position (    
gill slits4 h4br4a41 hypobran*ial art]y4
 ,h4,s41 hepatic s9us4 i4j4s41 inf]ior  
jugul> s9us 7 ext]nal jugul> ve974 ,k41 
kidney4 ,l4,v41 lat]al ve94 oe4s41      

v5tral wall ( oesophagus4 ,p4,c4,c41    
p]ic>dial cavity4 ,p4,c4,s41 po/]ior    
c>d9al s9us4 p4p4c41 p]ic>dio-p]itoneal 
canal4 ,p4,v41 portal ve94 r4p4v41      
r5o-portal ve94 s4c4v41 subclavian ve94 
,vn41 v5tricle4 -v4s4v41 inf]ior 7      
ext]nal7 jugul> ve9-4  ,figure #d4      
,skeleton ( pectoral limb1 & girdle4--  
g41 ! girdle 7also 9 ,figure #c74 m4p41 
meso-pt]ygium4 mt4p41 meta-pt]ygium4    
p4p41 pro-pt]ygium4 sc41 its dorsal     
portion4  ,illu/ration3 ,diagram ,%eet  
#af4     ,%eet #ag  -,! ,uro-g5ital     
,organs ( ! ,dog-,fi%4  ,figure #a4 ,!  
,female1 ! oviduct ( ! left side cut    
away1 -& an egg case 9 ! oviduct4-      
,figure #b4 ,! ,male4  ,! rectum is     
remov$ 9 bo? cases1 & ! silv]y p]itoneum
 dissect$ (f f ! kidneys4  ,figure #c4  
,a g5]aliz$ diagram ( ! uro-g5ital      
organs4-- ,all ref]5ces 9 text4 ,ms41 ! 
mesonephros1 is ! epididymis 9 ! male1 &
 is r$uc$ 9 ! female2 ,ms4d41 its duct1 
is ! vas def]5s 9 ! male1 & p]si/s only 
z ! ur9>y receptacle 9 ! female4 ,mt4 & 

,mt4d41 ! metanephros & metanephric     
duct1 become ! functional kidney & uret]
 9 bo? sexes4 ,g4 is ! gonad            
7reproductive gl&71 & ,m4,l4 ! animal's 
middle l9e 7m$ian plane74 -,ps4-1 ,pr41 
! pronephros1 is nev] develop$ 9 !      
,dog-fi%2 ,p4d41 its suppos$ duct1 is ! 
oviduct ( ! female1 & is suppress$ 9 !  
male4  ,illu/ration3 ,diagram ,%eet #ag4
     ,%eet #ah4  ,figure #a4 ,!         
,dog-,fi% ,bra91 dorsal view4  ,figure  
#b4 ,m$ian section ( ! same4 ,to ! "r a 
m diagrammatic figure4 ,! n]ves are     
numb]$3-- ,,br#a1 ,,br#b1 ,,br#c1 ,,br#d
 bran*es ( ,x =k+ ov] ! second to ! fif?
 gillslit4 cb41 c]ebellum4 h4s4c41      
horizontal semi-circul> canal ( e>1     
expos$ by ! slic+ d[n ( ! otic mass4    
,,lat41 lat]al-l9e bran* ( ,x4 m4o41    
m$ulla oblongata4 oph41 oph?almic n]ve  
7,v4#a,,vii4#a74 op4l41 optic lobe4     
pit41 pituit>y body4 pr4c41             
pros5cephalon 7c]ebral hemisph]e74 rh41 
olfactory lobe 7rh95cephalon74 r4t41    
-its- re/i=m tracts ( m$ulla4 -/-4      

,s4,p4,g41 /alk ( ! p9eal gl&4 ?41      
?alam5cephalon4 ?4c41 ?alam5cephalon4   
-ut41 ! utriculus1 se5 ?r\gh !          
semi-transp>5t c>tilage-4 ,vid41 !      
,vidian bran* ( ,,vii4 ,visc41 visc]al  
bran* ( ,x4  ,figure #c4 ,diagram ( ! e>
 ( a fi%4 ,! /ructure ( ?is is easily   
made out by cle>+ otic capsule & cutt+  
slices ( ! c>tilage 9 ! ,dog-,fi% 7e4g41
 ,figure #a1 h4s4c474  amp41 _!         
ampullae4 a4v4c41 p4v4c41 h4c41 ant]ior1
 po/]ior1 horizontal canal respectively4
 amp41 ! ampullae4 d4e41 ! ductus       
endo-lymphaticus4 -sac41 ! sacculus2 c41
 a small outgr[? ( ! latt]1 correspond+ 
to ! rabbit's co*lea-4 -ut41 !          
utriculus-4   ,figure #d4 ,! cranium &  
bran*ial b>s ( a ,dog-,fi%4 ,! groove 9 
! otic capsule connects ! orbital &     
ant]ior c>d9al s9uses4  ,a4,c4,s41      
position ( ! ant]ior c>d9al s9us 7dott$ 
outl9e74 c41 ! v]tebral c5tra4 c4b41 !  
c]ato-bran*ial4 c4h41 ! c]ato-hyal4     
e4b41 epi-bran*ial4 ex4b41              
extra-bran*ial4 h4,m41 ! hyo-m&ibul>4   

i4n4p41 int]-neural plate4 ,m4,c41      
,meckel's 7l[] jaw7 b>4 ,na4,c41 ! nasal
 capsule4 n4p41 neural plate4 n4s41     
neural sp9e4 ,ot4,c41 ! otic capsule4   
ph4b41 ! ph>yngo-bran*ial4 ,p4pt41 !    
palato-pt]ygoid b> 7upp] jaw b>74 p4s41 
pre-spiracul> ligam5t1 conta9+ a        
c>tilag9\s nodule4 r41 rib4 sp41 !      
position ( ! spiracle4  ,figure #e4     
,diagrams ( a v]tebral c5trum4-- ,=     
ref]5ce lett]s1 see text 7,section #i74 
,no ,figure #f1 9 ,fir/ ,edition4       
,figure #f4 ,diagram = comp>ison )      
,figure ,,iii41 ,%eet #i4  ,illu/ration3
 ,diagram ,%eet #ah4     ,%eet #ai4     
,figure #a4 ,amphioxus1 se5 f ! "r side4
 a----b %[s ! natural size4 ,! animal is
 suppos$ to be cl>ifi$1 & m\nt$ 9 "s    
highly refract+ m$ium1 s t x is         
practically transp>5t2 ,i41 ,,ii41      
,,iii41 & etc41 ref] to ! section figur$
 on ,%eet #bj4  ,figure #b4 ,amphioxus1 
,g5]al ,dissection4 7,slightly alt]$ f a
 figure by ,pr(essor ,e4 ,r4 ,lanke/]47 
,! v5tral atrial wall is remov$4 ,!     

ph>ynx cut away f ! dorsal body-wall1 & 
) ! true v5tral body-wall turn$ ov] to !
 7animal's7 "r4 ,! arr[ a41 a41 passes  
?r\gh anus to inte/9e2 b41 b41 is ?ru/  
?r\gh ! atrial pore to ! atrial cavity4 
,note coe41 ! body cavity4  ,ref]5ces to
 ! two figures4 an41 anus4 at41 atrial  
cavity4 at4w41 atrial wall4 at4p41      
atrial pore4 a4d41 ant]ior dilatata (   
n]v\s sy/em4 b4w41 body-wall4 b4t4,l41  
br[n tubes ( ,lanke/]4 c4f41 ciliat$    
funnel4 coe41 coelome4 c4ao41 c>diac    
aorta4 d4ao41 dorsal aorta 7pair$74     
d4ao'41 dorsal aorta m$ian4 g41 gonads  
7male or female g5ital gl&74 hep41      
hepatic ve94 941 inte/9e4 i4w41 inte/9e 
wall4 lv41 liv]4 m4f41 m$ian f94 n4c41  
noto*ord4 p4v41 portal ve94 ph41 ph>ynx4
 -p4s4-1 e4s4 pigm5t spot 7eye spot74   
s4c41 sp9al cord4  ,illu/ration3        
,diagram ,%eet #ai4     ,%eet #bj       
-,sections ( ,amphioxus4  ,! ,roman     
num]als indicate ! correspond+ region 9 
,figure #a1 ,%eet #ai4 ,! lett]+ is     
id5tical2 b note1 9 addition2 br4c41    

bran*ial canal4 c4f41 ciliat$ funnel4   
d4c4c41 dorsal coelomic canal4 end41    
endo/yle4 ep41 epipleur4 e4s41 eye spot4
 h4p41 hypoph>yngeal grove4 h4vn41 =    
hepatic ve94 o4c41 oral cavity 7or      
hood74  ,illu/ration3 ,diagram ,%eet    
#bj4     ,%eet #ba4  -,phases 9 !       
,developm5t ( ,amphioxus4  ,figures #a1 
#b1 #c1 #d4 ,phases 9 segm5tation4      
,figure #e4 ,! bla/osph]e4  ,figure #f4 
,! ga/rula 9 section1 ant]ior end to !  
"r4  ,figure #g4 i4 ,dorsal view po/    
ga/rula /age4  ,figure #g4 ii4          
,diagrammatic section ( ! same 9 !      
position indicat$ by ! transv]se l9e 9  
#g1 i4  ,figure #h4 ,diagrammatic       
section ( a lat] /age4 coe4p41 !        
coelomic p\*es4 n4c41 ! noto*ord4 n4p41 
! neural plate4  ,figure #i4;i4 ,/ill   
lat] section4  ,figure #i4 ii4          
,diagrammatic view ( late embryo4       
,figures #aj1 #aa1 #ab illu/rate !      
=mation ( ! atrium z a m$ian v5tral     
invag9ation1 at4  ,illu/ration3 ,diagram
 ,%eet #ba4     ,%eet #bb4  -,!         

,developm5t ( ! ,frog4  ,^! diagrams mu/
 be /udi$ ) ! text4 ,!y %\ld be comp>$ )
 ! correspond+ ones ( ,amphioxus z      
indicat$ bel[4  ,figures #a1 #b1 #c4    
,/ages 9 segm5tation 7comp>e #a1 #b 1#c 
( ,%eet #ba ,amphioxus74  ,figure #d4   
,bla/osph]e /age 7comp>e #e1            
,amphioxus74 ,?is1 on a small] scale4 ,!
 cells on ! v5tral side are s mu* l>g]  
because di/5d$ ) yolk4  ,figure #e4     
,ga/rula /age 9 section 7comp>e #f1     
,amphioxus74 ,! ,frog on a small] scale 
?an ,amphioxus4  ,figure #f4 ,dorsal    
view ( ga/rula 7comp>e #g1 ,amphioxus74 
,figure #g4 ,"p ( a transv]se section ( 
develop+ tadpole1 correspond+ to ,figure
 #h ( ,amphioxus4  ,figures #h & #i4    
,diagrammatic longitud9al sections (    
tadpoles 7comp>e #i4 ii4 ( ,amphioxus74 
,y4 repres5ts a mass ( yolk cells4      
,figure #aj4 ,side view ( "y tadpole1   
%[+ ext]nal gills 7e4g47 & suck]s 7s474 
,note ! v5tral bulg+ due to ! yolk4     
,figure #aa4 ,v5tral view ( a lat]      
tadpole4 op41 ! op]culum4 int41 coil+   

inte/9e4  ,figure #ab4 ,head ( /ill lat]
 tadpole 9 horizontal section to %[     
atrial *amb] =m$ by op]culum4 int4g41   
int]nal gills4 ,l41 develop+ lungs4     
,figure #ac4 ,diagrammatic cross-section
 ( ! mid-dorsal "p ( an embryonic       
v]tebrate4  ao41 aorta4 ,b4,c41 ,b[man's
 capsule4 coe41 coelom4 d4g41 ganglion  
on dorsal root ( sp9al n]ve4 gl41 -its  
bran*- art]iole to =m glom]ulus4 g4r41  
g5ital ridge4 ,i41 inte/9e4 ,m4,d41     
,mull]ian duct4 ns4 n/41 nephro/ome4    
n4c41 noto*ord2 -n4s4-1 n4%4 its %ea?4  
s4c41 neural canal4 ,w4,d41 ,wolffian   
duct4  ,illu/ration3 ,diagram ,%eet #bb4
     ,%eet #bc4  -,! ,developm5t ( !    
,f[l4  ,figure #a4 ,diagram ( ! e>ly    
ovum4 ,! section bel[ is a small portion
 ( ! bla/od]mic area4 b4d41 bla/od]m4   
y41 ! undivid$ yolk4 s4c41 ! segm5tation
 betwe5 ! bla/od]m & yolk4 ,comp>e s4c4 
9 ,%eet #bb1 ,figure #d4  ,figure #b4   
,area pellucida ab\t ! sixte5? h\r4 ,!  
figure bel[ is ! c5tral "p ( ! section  
indicat$ by ! transv]se l9e1 & %[+ !    

primitive /reak 7p4s474  ,figure #c4    
,area pellucida ab\t ! tw5ty-fir/ h\r4  
,two sections ?r\gh a & b bel[4  ,figure
 #d4 ,ab\t ! tw5ty-fif? h\r2 surface    
view2 longitud9al section to "r &       
transv]se above4  ,figure #d;b4         
,diagrammatic r5d]+ ( same /age 7comp>e 
,figure #i ( ,frog & #i4;ii4            
,amphioxus74 ,?is w be mo/ cle>ly       
und]/ood if ! read] look at ,%eet #bb1  
,figure #i1 & imag9e ,y4 enorm\sly      
increas$1 & ! embryo s9k+ into x4       
,epibla/1 ep41 -l9e ( da%es- black l9e4 
,mesobla/1 dott$4 ,hypobla/1 -black- l9e
 ( da%es4 pp41 ! pleuro-p]itoneal       
cavity4  ,figure #e & #f illu/rate      
=mation ( amnion 7a47 & allantois       
7all474 #f is ab\t ! f\r? day4          
,illu/ration3 ,diagram ,%eet #bc4       
,%eet #bd4  -,! ,developm5t ( ! ,f[l4   
,figure #a4 ,*ick ab\t ! -fif?- ?ird    
day4 ,at ?is /age ! *ick lies on its    
left side 9 ! yolk4 ,= lett]+ ( blood   
vessels1 see 7#g7 bel[4 i41 ! inte/9e4  
u4v41 ! yolk sac4 v4v41 ! vitell9e ve9s4

 al41 ! allantois4  ,figure #b4 ,*ick   
ab\t six? day4  ,figure #c4 ,developm5t 
( he>t4  ,figure #d4 ,developm5t ( !    
eye4  ,figure #e4 ,*ick ab\t ! sixte5?  
day4 ,a4,m4 is ! amnion surr\nd+ !      
embryo4 ,note p>ticul>ly h[ ! allantois 
7al47 has spread ov] surface ( %ell & h[
 ! yolk sac is %rivell$4  ,figure #f4   
,figures to illu/rate ! relative        
function & importance ( allantois & yolk
 sac 9 bird & mammal4 ,9 ! f[l1 h[ev]1 !
 blood-vessels ( ! allantois also       
probably absorb ! album5 ( ! egg1 & may 
excrete urea into ! egg-space4  ,figure 
#g4 ,simplifi$ figure ( ! embryonic     
circulation1 = comp>ison ) ! simil>     
figures annex$ to ,dog-,fi% & ,rabbit4  
,l9es f ,second ,edition only4 ,a4,c41  
ant]ior c>d9al4 ,ao41 ,aorta4 ,br#d1    
six? aortis ar* 7f\r? bran*ial74 ,c4,s4 
,cuvi]ian s9us4 ,h41 ! he>t4 ,i4,c41    
inf]ior cava4 ,p4,c41 po/]ior c>d9al    
ve94 ,tr4,a41 truncus art]iosus4 v4v41  
vitell9e ve94  ,figure #h4 ,*ick on !   
n9ete5? day4  ,illu/ration3 ,diagram    

,%eet #bd4