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autonomic nervous system of the ratfish Hydrolagus colliei Paul, Frank 1949

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Crp.  I  THE AUTONOMIC NERVOUS SYSTEM OF THE RATFISH, Hydrolagu3 c o l l l e l  by  Frank  Paul  A Thesis submitted i n p a r t i a l f u l f i l m e n t o f the r e q u i r e m e n t s  f o r t h e degree o f  MASTER OF ARTS I n t h e Department of ZOOLOGY  The U n i v e r s i t y o f B r i t i s h Columbia A p r i l , 19.49  ii  Abstract Young immature specimens o f Hydrolagus  colllel,were  f i x e d i n v a r i o u s f i x i n g f l u i d s and s t a i n e d w i t h e o s i n and h e m a t o x y l i n , M a l l o r y ' s t r i p l e s t a i n , Bodian's p r o t a r g o l , and Holmes' s i l v e r method.  Gross d i s s e c t i o n s of the autonomic  r system were c a r r i e d out w i t h the use o f osmium t e t r o x l d e and Nelson's  " i n toto" s t a i n f o r nerves. The  c r a n i a l autonomic system appears t o b e s i m i l a r  to t h a t o f o t h e r s e l a c h i a n s , except f o r t h e p e c u l i a r i t i e s o f the vagus.  The f o u r v a g a l g a n g l i a a r e s e p a r a t e d f r o m  one  a n o t h e r ; the v i s c e r a l b r a n c h o f the vagus sends a'branch t o the p r e g a s t r i c g a n g l i o n , and the r e m a i n i n g f i b r e s the a n t e r i o r p o r t i o n o f t h e d i g e s t i v e tube, the o f which,  i s predominantly  surrounded  striated.  supply musculature  The g a s t r i c g a n g l i o n i s  by a l a r g e mass o f s u p r a r e n a l t i s s u e ;  t h e y a r e termed the a x i l l a r y body.  together  The h e a r t r e c e i v e s o n l y  a v a g a l s u p p l y , the f i b r e s o f w h i c h a r e i n the w a l l s o f the s i n u s venosus and a u r i c l e s ; no f i b r e s make c o n t a c t w i t h t h e . ventricles. The s y m p a t h e t i c arranged.  g a n g l i a a r e , as a r u l e ,  segmentally  The f i b r e s c o n n e c t i n g the g a n g l i a a r e n o t  o r g a n i z e d i n t o a d e f i n i t e t r u n k as found i n h i g h e r v e r t e b r a t e s , but seem t o c o u r s e a t random between the g a n g l i a .  Associated  w i t h the sympathetic g a n g l i a a r e the s u p r a r e n a l b o d i e s , which  ill  a r e l i m i t e d to the abdominal c a v i t y .  The  anterior  portion  o f the k i d n e y s a p p e a r s segmented; p o s t e r i o r l y t h e y f u s e are not  segmented.  The  i n t e r r e n a l body i s s i t u a t e d i n  c e n t r e o f the f u s e d k i d n e y . to the i n t e r r e n a l .  The  the  There i s no autonomic s u p p l y  s a c r a l o u t f l o w from the s p i n a l c o r d  i s a b s e n t as i t i s i n a l l f i s h . the vagus extends i n t o the  The  l a t e r a l line'branch  t i p o f the t a i l ;  l a t e r a l l y to the open l a t e r a l l i n e c a n a l . s y m p a t h e t i c s u p p l y to the t a i l r e g i o n ,  of  i t sends f i b r e s There i s no  as the  sympathetic  system ends w i t h the k i d n e y i n t h e p o s t e r i o r p r o j e c t i o n the abdomen.  and  of  i  T a b l e o f Contents  Abstract  11  Introduction  iv  H i s t o r i c a l Review  1  Mammalian Autonomic System  9  Anatomy  9  Function  13  S e l a c h i a n System  14  M a t e r i a l s and Methods  16  C r a n i a l Autonomic Nervous System  22  Sympathetic System  25  A n t e r i o r Abdominal R e g i o n  26  P o s t e r i o r Abdominal R e g i o n  29  Suprarenal Tissue  °  30  Interrenal Tissue  31  Sympathetic System i n T a i l  33  Discussion  33  Summary  40  Acknowledgements  42  iv  THE AUTONOMIC NERVOUS SYSTEM OP THE ' RATPISH, Hydrolagus c o l l i e i  Introduction The  autonomic n e r v o u s system has r e c e i v e d a g r e a t  d e a l o f s t u d y , b o t h a n a t o m i c a l l y and p h y s i o l o g i c a l l y . However, most o f t h e i n t e r e s t i s c e n t r e d on t h e h i g h e r b r a t e s , e s p e c i a l l y t h e Mammals.  Among t h e l o w e r  verte-  vertebrates,  r e p r e s e n t a t i v e s f r o m a l l c l a s s e s have r e c e i v e d some s t u d y ; but t h e r e a r e s ome groups t h a t have r e c e i v e d l i t t l e a t t e n t i o n . The  f a m i l y Chimaeridae b e l o n g t o such a group.  Although  t h e r e i s an e x c e l l e n t a c c o u n t o f t h e autonomic nervous system of s e l a c h i a n s , t h e l i t e r a t u r e o f t h i s system I n c h i m a e r o i d s i s very  scanty. The  c h i m a e r o i d s a r e a h i g h l y s p e c i a l i z e d group,  h a v i n g descended from t h e same a n c e s t r a l f o r m as t h e s e l a c h i a n s , r a t h e r than r e p r e s e n t i n g of the s e l a c h i a n s .  the ancestral d e r i v a t i o n  T h i s group e x h i b i t s many p r i m i t i v e  c h a r a c t e r i s t i c s , possessing  an Independent e v o l u t i o n d i s -  t i n c t l y separate from other S e l a c h i i .  Evidence o f t h e i r  p o s i t i o n i n t he e v o l u t i o n a r y s c a l e i s d e r i v e d from  paleonto-  l o g i c a l e v i d e n c e , w h i c h i s based upon f o s s i l s d a t i n g back t o the J u r a s s i c p e r i o d , whereas those o f t h e s h a r k s and r a y s a n t e d a t e d t h e Permian e r a .  Historical  The v i t a l are  Review  f u n c t i o n s o f t h e body t o v a r y i n g degrees  s u b j e c t t o t h e c o n t r o l o f t h e nervous system.  Some  f u n c t i o n s a r e c o n t r o l l e d e n t i r e l y by t h i s system; w h i l e o t h e r s a r e connected w i t h i t o n l y i n d i r e c t l y and between these two extremes a r e v a r y i n g degrees o f dependency.  Mental  p r o c e s s e s a r e an example o f d i r e c t nervous c o n t r o l , whereas humoral c o n t r o l o f p h y s i o l o g i c a l f u n c t i o n s i s an example o f i n d i r e c t nervous  control.  E a r l y i n t h e development  o f s c i e n t i f i c thought man  d i v i d e d t h e a c t i v i t i e s o f t h e body i n t o two groups, t h o s e o f v o l i t i o n , i . e . those o v e r w h i c h he had c o n t r o l and t h o s e t h a t were s t r i c t l y had no c o n t r o l .  I n v o l u n t a r y , i . e . t h e ones o v e r w h i c h he  T h i s i d e a p r e v a i l e d some time b e f o r e an  attempt was made t o a t t r i b u t e t h e s e f u n c t i o n s t o a n a t o m i c a l structures, Galen was t h e f i r s t t o g i v e an a n a t o m i c a l d e s c r i p t i o n of  any p a r t o f the autonomic nervous system.  In h i s  d i s s e c t i o n s he saw a n e r v e t r u n k l y i n g a l o n g t h e necks o f the  r i b s , w h i c h r e c e i v e d f i b r e s from t h e s p i n a l c o r d and  gave o f f branches t o t h e v i s c e r a .  Galen assumed t h i s nerve  to be a b r a n c h o f t h e vagus and advanced t h e t h e o r y t h a t through I t t h e v i s c e r a r e c e i v e d s e n s i t i v i t y from t h e b r a i n and motor power from t h e s p i n a l c o r d .  He was t h e f i r s t t o  -  2  -  advance the t h e o r y o f "sympathy" o r "consent" between d i f f e r e n t p a r t s o f the body.  He thought t h a t the d i s t r i b u t i o n  o f a n i m a l s p i r i t s was brought about by the p e r i p h e r a l n e r v e s , w h i c h he r e g a r d e d as t u b u l a r s t r u c t u r e s .  Before Galen,  A r i s t o t l e had t a u g h t t h a t the b r a i n s e r v e s to c o o l the b l o o d , however Galen gave i t the f u n c t i o n of i n d u c i n g the " a n i m a l " spirits.  He r e g a r d e d the v a g i as the s i x t h p a i r o f c r a n i a l  n e r v e s , thus assuming  t h a t the g a n g l i o n a t e d s y m p a t h e t i c t r u n k  and the vagus n e r v e were a p h y s i o l o g i c a l and a n a t o m i c a l u n i t . The vagus n e r v e was 1545 by E t i e n n e .  s e p a r a t e d f r o m the s y m p a t h e t i c t r u n k i n  The f i r s t t o i n t r o d u c e the p h y s i o l o g i c a l  concept o f i n v o l u n t a r y , as d i s t i n c t from v o l u n t a r y movements was W i l l i s i n 1664.  He e r r o n e o u s l y a t t r i b u t e d the i n i t i a t i o n  o f i n v o l u n t a r y movements t o t h e c e r e b e l l u m .  Weber and h i s  a s s o c i a t e s e s t a b l i s h e d through e x p e r i m e n t a l s t u d i e s the i n h i b i t o r y a c t i o n o f the vagus upon the h e a r t b e a t .  Whytt,  1751, was the n e x t p e r s o n to c o n t r i b u t e t o the i n v e s t i g a t i o n o f t h e autonomic nervous system.  His i n t e r p r e t a t i o n of  i n v o l u n t a r y mcv ement on t h e b a s i s o f l o c a l s t i m u l a t i o n paved the way f o r the t h e o r y of r e f l e x a c t i o n .  The  peristaltic  a c t i o n o f the i n t e s t i n e and the c o n t r a c t i o n of the u r i n a r y b l a d d e r were responses o f the m u s c u l a t u r e t o l o c a l  excitation  o f the mucous membrane o r s t r e t c h i n g o f muscle f i b r e s due t o d i s t e n t i o n o f the organs.  He i n t r o d u c e d t h e concept t h a t a l l  "sympathy" between v a r i o u s p a r t s o f the body must be  brought  about by the n e r v e s , b u t n o t by the a c t u a l f l o w of any s t a n c e : f o r he observed t h a t sympathy may  sub-  o c c u r between p a r t s  of  the body w h i c h a r e n o t connected d i r e c t l y by n e r v e s .  It  was n o t u n t i l some time l a t e r t h a t i n v e s t i g a t o r s r e c o g n i z e d the f a c t t h a t the communicating  rami c o n s t i t u t e the o n l y  pathway between the c e n t r a l nervous  system and the s y m p a t h e t i c  ganglia. W i l l i s i n h i s i n v e s t i g a t i o n s had c a l l e d the s y m p a t h e t i c t r u n k s the " i n t e r c o s t a l " n e r v e s .  Winslow d i s -  c a r d e d t h i s term and s u p p l i e d , as an a l t e r n a t i v e name, the " g r e a t s y m p a t h e t i c n e r v e s " , because i n h i s o p i n i o n t h e y were concerned w i t h the sympathies between v a r i o u s p a r t s o f the body.  The i n v e s t i g a t i o n s o f Johnstone l e d him t o b e l i e v e  t h a t the s y m p a t h e t i c g a n g l i a were the s t r u c t u r a l u n i t s through w h i c h the movements o f the v i s c e r a a r e r e n d e r e d involuntary.  H i s assumption was  that they i n t e r c e p t  and  p r e v e n t them from r e a c h i n g c e r t a i n p a r t s o f the body.  His  d e s c r i p t i o n o f the n e r v e s and t h e i r r e l a t i o n s h i p w i t h the g a n g l i o n l e d t o the use o f the terms " g a n g l i o n i c n e r v e s " " g a n g l i o n i c nervous  system".  and  The c u r r e n t concepts o f  " s o m a t i c " and " v i s c e r a l " f u n c t i o n s were d e r i v e d from t h e s t u d i e s o f B i c h a t , whose c o n c e p t i o n o f v i t a l a c t i v i t y  was  based on two components, namely, a n i m a l l i f e and o r g a n i c l i f e , hence the terms " s o m a t i c " and " v i s c e r a l " . to  He was  the f i r s t  r e g a r d the s y m p a t h e t i c g a n g l i a as nerve c e n t e r s e n t i r e l y  independent  o f the c e n t r a l nervous  system.  He a l s o r e c o g -  n i z e d the d i f f e r e n c e i n appearance o f the w h i t e and communicating  grey  rami, but u n f o r t u n a t e l y f a i l e d to r e a l i z e  t h e i r true s i g n i f i c a n c e . was  i n t r o d u c e d by R e i l .  The term " v e g e t a t i v e nervous  system"  He c o n s i d e r e d the communicating  rami  to be c o n n e c t i o n s between the a n i m a l and the v e g e t a t i v e nervous systems.  H i s c o n t e n t i o n was  that sensory s t i m u l i  from the v i s c e r a under normal c o n d i t i o n s do n o t r e a c h the b r a i n ; but t h a t i n d i s e a s e the s e n s o r y s t i m u l i from the v e g e t a t i v e system a r e t r a n s m i t t e d through the  communicating  rami and thus r e a c h the l e v e l o f c o n s c i o u s n e s s . The d e s c r i p t i o n o f the n e r v e c e l l b o d i e s i n sympat h e t i c g a n g l i a by Ehrenberg i n 1833, i n i t i a t e d  further  o b s e r v a t i o n s on t h e m i c r o s c o p i c s t r u c t u r e o f s y m p a t h e t i c g a n g l i a and t h e i r c e l l s and o f n e r v e f i b r e s . w h i t e communicating  F i b r e s o f the  rami were r e c o g n i z e d as a r i s i n g i n the  s p i n a l c o r d and e n t e r i n g the sympathetic g a n g l i a ; some t o pass t h r o u g h the g a n g l i o n ; o t h e r s t e r m i n a t e i n the g a n g l i o n . M e i s s n e r d e s c r i b e d the submucous p l e x u s i n the i n t e s t i n e and Auerbach,  the m y e n t e r i c p l e x u s .  Claude Bernard's d i s c o v e r y  o f the vasomotor f u n c t i o n o f the sympathetic n e r v e s t o the b l o o d v e s s e l s was l a t e r c o n f i r m e d by Brown-Sequdrd. e a r l y s t u d i e s l e d to the erroneous concept t h a t a l l  These sympathetic  nerve f i b r e s t o b l o o d v e s s e l s were v a s o c o n s t r i c t o r s . o b s e r v a t i o n s by B e r n a r d r e c t i f i e d t h i s e r r o r .  He  Later  demonstrated  t h a t s t i m u l a t i o n o f the chorda tympani caused d i l a t i o n o f the b l o o d v e s s e l s s u p p l y i n g the s u b m a x i l l a r y g l a n d . B e r n a r d f o r m u l a t e d the h y p o t h e s i s t h a t a l l  Later  sympathetic  r e f l e x e s a r e mediated t h r o u g h the s p i n a l c o r d .  - 5 -  The work o f G a s k e l l r e p r e s e n t s  the n e x t  great  c o n t r i b u t i o n t o the u n d e r s t a n d i n g o f t h e autonomic nervous system.  He gave an adequate a n a t o m i c a l and h i s t o l o g i c a l  account o f t h e w h i t e communicating r a m i and t h e i r distribution.  He r e c o g n i z e d  efferent ganglion  that the p e r i p h e r a l l y l o c a t e d  c e l l s a r e connected w i t h t h e c e n t r a l  nervous system by t h r e e o u t f l o w s  of medullated f i b r e s ,  namely the b u l b a r - t e c t a l , t h o r a c i c o - l u m b a r ,  and the s a c r a l .  He c l a s s i f i e d t h e s e g a n g l i a i n t o two c a t e g o r i e s , proximal  (1) t h e  o r v e r t e b r a l g a n g l i a w h i c h i n c l u d e o n l y the g a n g l i a  of t h e s y m p a t h e t i c t r u n k s from t h e l o w e r c e r v i c a l segments downward and (2) d i s t a l g a n g l i a w h i c h he s u b d i v i d e d groups (a) p r e v e r t e b r a l g a n g l i a i . e . t h e s u p e r i o r c o e l i a c and s u p e r i o r m e s e n t e r i c and (b) t e r m i n a l  i n t o two cervical,  ganglia  i . e . those l o c a t e d w i t h i n v i s c e r a l organs o r a d j a c e n t t o them.  E f f e r e n t neurons t h a t a r e s i t u a t e d o u t s i d e o f the cen-  t r a l nervous system and i n n e r v a t e  involuntary  structures  were named by G a s k e l l as t h e " i n v o l u n t a r y nervous system". He r e g a r d e d t h i s system as p u r e l y motor i n f u n c t i o n .  This  c l a s s i f i c a t i o n i s open t o s e v e r e c r i t i c i s m and has never been w i d e l y used. Prom s t u d i e s on the r e l a t i o n between the p e r i p h e r a l g a n g l i o n and t h e i r n e r v e s , L a n g l e y proposed a new of t h e system o f n e r v e s . system".  terminology  He termed i t t h e "autonomic nervous  When t h i s term came i n t o usage, i t was a w e l l known  f a c t t h a t the o u t f l o w s  o f t h e c e n t r a l nervous system c o n s i s t e d  -  6  -  o f t h r e e p a r t s : the c r a n i a l , the t h o r a c i c o - l u m b a r and  the  s a c r a l ; and t h a t the t h o r a c i c o - l u m b a r o u t f l o w sent branches to a l l p a r t s o f the body, whereas the c r a n i a l and s a c r a l o u t f l o w s s u p p l i e d o n l y c e r t a i n p a r t s o f the body.  Prom  p h y s i o l o g i c a l s t u d i e s i t became known t h a t the f u n c t i o n a l a c t i v i t y of the c r a n i a l and s a c r a l r e g i o n were a l i k e and  that  t h e i r f u n c t i o n a l e f f e c t s were o p p o s i t e to those o f the thoracico-lumbar outflow.  Thus the t h o r a c i c o - l u m b a r  outflow  came to be r e g a r d e d by L a n g l e y as a system d i s t i n c t from the o t h e r autonomic components.  He d i v i d e d the c r a n i a l o u t f l o w  I n t o two p a r t s , f o r he saw t h a t the f i b r e s s u p p l y i n g the eye were d i s t i n c t from the b u l b a r p a r t o f the c r a n i a l o u t f l o w . He regarded  the b u l b a r and s a c r a l o u t f l o w s as a s i n g l e system  w h i c h i n n e r v a t e s the v i s c e r a .  On these assumptions he  d i v i d e d the autonomic system i n t o the " t e c t a l " , " b u l b o - s a c r a l " and " s y m p a t h e t i c "  systems.  A few y e a r s l a t e r he r e v i s e d  t h i s c l a s s i f i c a t i o n f o r i t was  discovered that adrenalin  produced the same e f f e c t s as s t i m u l a t i o n o f nerves and t h a t c e r t a i n o t h e r drugs,  sympathetic  such as a c e t y l c h o l i n e ,  p h y s o s t i g m i n e , and p i l o c a r p i n e , produced e f f e c t s  identical  to those produced by s t i m u l a t i o n o f t e c t a l and b u l b o - s a c r a l nerves.  I n accordance w i t h these f a c t s he grouped the t e c t a l  and b u l b o - s a c r a l autonomic n e r v e s t o g e t h e r and c a l l e d group the p a r a s y m p a t h e t i c  system.  Langley regarded  neurons o f the submucous and m y e n t e r i c p l e x u s e s as  this  the postgang-  l i o n i c neurons i n b u l b a r and t e c t a l e f f e r e n t c h a i n s but  the  i n f o r m a t i o n a v a i l a b l e g a v e h i m no p r o o f o f s u c h  central  c o n n e c t i o n s ; t h e r e f o r e he p l a c e d t h e submucous a n d plexuses  i n t o a s e p a r a t e system,  Langley regarded  the e n t e r i c nervous  system.  the f u n c t i o n s of the autonomic nerves  being e s s e n t i a l l y motor. i s not without f a u l t , t h a t has  myenteric  been proposed  Although Langley's  classification  i t i s t h e most s a t i s f a c t o r y to date.  I t i s as  as  terminology  follows:  Autonomic Nervous System  Parasympathetic  Ocular  Oro-anal  Tectal Autonomic  The  Bulbar Autonomic  Sacral Autonomic  only other c l a s s i f i c a t i o n  proposed  the f o l l o w i n g  Sympathetic  of note  terminology:  Thoracico lumbar Autonomic  Enteric Plexuses Auerbach and Meissner  i s that of Pulton  who  of  - 8 -  Cerebral Cortex  Corpus S t r i a t u m  Hypothalamus  Nerve^No. I l l  No ?s viI a  a  6 r  iX  S  -Midbrain Region  xT  B u l b a r  R  e  S  l  o  n  Parasympathetic  Parasympathetic  Parasympathetic  S p i n a l Cord Upper T h o r a c i c to >Lower Lumbar Sacral  -Sympathetic  Parasympathetic  o  Mammalian System  Anatomy: The n e r v e s o f t h e body can be d i v i d e d i n t o two groups, a f f e r e n t o r s e n s o r y f i b r e s , which l e a v e t h e c e n t r a l nervous system by means o f t h e d o r s a l r o o t , and e f f e r e n t o r motor f i b r e s w h i c h l e a v e t h e c e n t r a l nervous system by means of the v e n t r a l root. subdivided  These two groups o f f i b r e s a r e f u r t h e r  depending on t h e i r f u n c t i o n a l n a t u r e and t h e  s t r u c t u r e s w h i c h they i n n e r v a t e .  The a f f e r e n t f i b r e s t h a t  a r e d i s t r i b u t e d t o t h e s e n s o r y endings I n t h e body, e x c e p t those t o t h e v i s c e r a a r e termed somatic a f f e r e n t f i b r e s ; whereas those f i b r e s d i s t r i b u t e d t o t h e s e n s o r y endings i n the v i s c e r a a r e termed v i s c e r a l a f f e r e n t f i b r e s .  The term  v i s c e r a i n c l u d e s a l l organs and p a r t s o f t h e body t h a t a r e concerned w i t h i t s maintenance and r e p r o d u c t i o n .  Of t h e  e f f e r e n t f i b r e s , those t h a t s u p p l y t h e v o l u n t a r y m u s c u l a t u r e o f t h e body a r e c a l l e d somatic e f f e r e n t f i b r e s , as opposed t o those f i b r e s t e r m i n a t i n g  i n g l a n d s o r smooth muscles o f  the v i s c e r a w h i c h a r e termed v i s c e r a l e f f e r e n t f i b r e s .  The  s p i n a l n e r v e s a r e mixed n e r v e s s i n c e they c o n t a i n b o t h a f f e r e n t and e f f e r e n t f i b r e s .  The v i s c e r a l e f f e r e n t com-  ponents o f t h e c r a n i a l and s p i n a l n e r v e s have been s e p a r a t e d from t h e s o m a t i c e f f e r e n t f i b r e s because o f s e v e r a l f a c t o r s . They pursue a d i f f e r e n t c o u r s e t h a n do t h e somatic e f f e r e n t fibres.  A v i s c e r a l Impulse a l w a y s i n v o l v e s two neurons i n  - 10  -  b e i n g conducted from t h e c e n t r a l nervous system t o the e f f e c t o r end o r g a n .  S i n c e the c l a s s i f i c a t i o n i s e s s e n t i a l l y  a f u n c t i o n a l one, the main d i f f e r e n c e between the two  systems  r e s t s i n the f a c t t h a t t h e v i s c e r a l e f f e r e n t r e f l e x e s a r e n o t subject to voluntary c o n t r o l .  Thus the v i s c e r a l  efferent  f i b r e s have become grouped i n t o a s e p a r a t e system^ t h e autonomic nervous system.  I t must be remembered t h a t t h i s  c l a s s i f i c a t i o n i s p u r e l y a f u n c t i o n a l one and t h a t I t has no d e f i n i t e a n a t o m i c a l b a s i s . S i n c e t h e t e r m i n o l o g y u s e d I s based a l m o s t e n t i r e l y upon the mammalian body, a b r i e f d e s c r i p t i o n o f the mammalian autonomic system w i l l be g i v e n .  According to the  c l a s s i f i c a t i o n o f L a n g l e y the autonomic system f a i l s  into  two main d i v i s i o n s , the s y m p a t h e t i c o r t h o r a c i c o - l u m b a r o u t f l o w and the p a r a s y m p a t h e t i c o r c r a n i o - s a c r a l o u t f l o w . The s y m p a t h e t i c d i v i s i o n c o n s i s t s o f two t r u n k s e x t e n d i n g l o n g i t u d i n a l l y t h r o u g h the neck, t h o r a x and abdomen on e i t h e r s i d e o f the v e r t e b r a l column.  Each t r u n k  i s composed o f a l i n e a r s e r i e s o f g a n g l i a connected by s t r a n d s o f nerve f i b r e s .  The s y m p a t h e t i c system t a k e s i t s  o r i g i n i n t h e c e l l s o f the l a t e r a l h o r n o f the s p i n a l c o r d , extending' from t h e f i r s t t h o r a c i c to t h e t h i r d segment.  lumbar  The f i b r e s o f t h e s e c e l l s a r e termed p r e g a n g l i o n i c  f i b r e s ; t h e y a r e m e d u l l a t e d and connect w i t h g a n g l i a o u t s i d e the s p i n a l c o r d .  situated  The c e l l s o f t h e s e o u t l y i n g g a n g l i a  g i v e r i s e t o axons w h i c h are n o n - m e d u l l a t e d and a r e termed  • •  I  -  postganglionic f i b r e s .  11  -  There i s no o u t f l o w o f f i b r e s f r o m  the c e r v i c a l p o r t i o n of t h e s p i n a l c o r d , but i n t h i s r e g i o n a r e s i t u a t e d t h r e e g a n g l i a , the s u p e r i o r c e r v i c a l g a n g l i o n , the m i d d l e c e r v i c a l g a n g l i o n and t h e i n f e r i o r c e r v i c a l ganglion.  These t h r e e g a n g l i a c o n s t i t u t e the a n t e r i o r p o r t i o n o f  the sympathetic  trunk.  The  s u p e r i o r c e r v i c a l .ganglion i s  the l a r g e s t o f the t h r e e g a n g l i a and i s s i t u a t e d a t t h e base o f the s k u l l .  Prom t h i s g a n g l i o n p o s t g a n g l i o n i c f i b r e s  i n n e r v a t e the eye, s u b m a x i l l a r y g l a n d , p a r o t i d g l a n d  and  t o g e t h e r w i t h f i b r e s f r o m t h e two o t h e r c e r v i c a l g a n g l i a comprise the sympathetic  i n n e r v a t i o n o f the h e a r t .  I n some  cases t h e r e i s a f u s i o n o f the i n f e r i o r c e r v i c a l and  the  f i r s t t h o r a c i c g a n g l i a to form the s t e l l a t e g a n g l i o n . t h e r e a r e vasomotor, p i l o m o t o r and r e s p e c t i v e areas o f I n n e r v a t i o n .  Also  s e c r e t o r y f i b r e s to the The r e m a i n i n g  sympathetic  t r u n k s u p p l i e s the r e s t o f the v i s c e r a and a s s o c i a t e d structures.  The  second t o f o u r t h t h o r a c i c branches send f i b r e s  to the b r o n c h i and l u n g s .  The  remaining  thoracic'segments  c o n s t i t u t e two o u t f l o w s , t h e g r e a t e r s p l a n c h n i c  nerve,  r e c e i v i n g the major c o n t r i b u t i o n o f f i b r e s and the l e s s e r splanchnic nerve.  These two n e r v e s c o n s i s t o f  myelinated  p r e g a n g l i o n i c f i b r e s p a s s i n g to the c o e l i a c g a n g l i o n . m a j o r i t y o f the f i b r e s synapse i n the g a n g l i o n and  The  postgang-  l i o n i c f i b r e s c o n t i n u e t o t h e i r i n s e r t i o n I n the stomach, l i v e r , ' pancreas,  i n t e s t i n e and k i d n e y .  The r e m a i n i n g  c o n t i n u e u n i n t e r r u p t e d t o the a d r e n a l medulla superior mesenteric  ganglion.  and  fibres  the  Those f i b r e s to t h e s u p e r i o r  - 12 -  mesenteric ganglion  synapse t h e r e and pass on t o t h e  I n t e s t i n e and rectum.  The  remaining  small  s y m p a t h e t i c f i b r e s pass  to the i n f e r i o r m e s e n t e r i c g a n g l i o n , h e r e they synapse and p o s t g a n g l i o n i c f i b r e s p r o c e e d t o the c o l o n , rectum, and g e n i t a l o r g a n s .  bladder  Each segment o f the s y m p a t h e t i c  g i v e s r i s e t o p o s t g a n g l i o n i c f i b r e s i n n e r v a t i n g the  trunk blood  v e s s e l s (vasomotor), the a r r e c t o r p i l l muscles ( p i l o m o t o r ) , and  sweat g l a n d s ( s e c r e t o r y f i b r e s ) . The p a r a s y m p a t h e t i c o r c r a n i o - s a c r a l o u t f l o w  o r i g i n a t e s a t t h r e e d i f f e r e n t l e v e l s I n t h e c e n t r a l nervous system, namely, the m i d b r a i n , p o r t i o n o f the s p i n a l c o r d .  the m e d u l l a , and  the s a c r a l  The p r e g a n g l i o n i c f i b r e s I s s u i n g  from the s p i n a l c o r d t e r m i n a t e  In ganglia s i t u a t e d w i t h i n or  i n c l o s e a s s o c i a t i o n w i t h the s t r u c t u r e s which they i n n e r v a t e . I n o t h e r words, the p r e g a n g l i o n i c f i b r e s o f t h i s system a r e l o n g and t h e p o s t g a n g l i o n i c f i b r e s a r e s h o r t as c o n t r a s t e d  to  the s h o r t p r e g a n g l i o n i c and l o n g p o s t g a n g l i o n i c f i b r e s o f the s y m p a t h e t i c system.  The  t h i r d c r a n i a l nerve gives  to p a r a s y m p a t h e t i c p r e g a n g l i o n i c f i b r e s to the  ciliary  g a n g l i o n w h i c h i n t u r n sends p o s t g a n g l i o n i c f i b r e s to c o n s t r i c t o r p u p i l l a e o f t h e eye.  The r e m a i n i n g  The  tenth  s e v e n t h and n i n t h i n n e r v a t e the  g l a n d s and t h e y synapse i n the s u b m a x i l l a r y g a n g l i o n o t i c ganglion r e s p e c t i v e l y .  The  the  cranial  s u p p l y t a k e s i t s o r i g i n i n t h e s e v e n t h , n i n t h , and c r a n i a l nerves.  rise  salivary and  vagus i s the o n l y c r a n i a l  s u p p l y t o the v i s c e r a ; and c o n s e q u e n t l y i t sends f i b r e s t o  - 13 a l l organs except the d i s t a l c o l o n , b l a d d e r , and  genital  organs, which d e r i v e t h e i r i n n e r v a t i o n f r o m the s a c r a l P i g . 2 shows a  f l o w o f the s y m p a t h e t i c .  diagrammatic  r e p r e s e n t a t i o n o f t h e mammalian autonomic nervous  system.  The s y m p a t h e t i c g a n g l i a a r e connected to the n e r v e s t h r o u g h the communicating the communicating  spinal  The f i b r e s c o m p r i s i n g  rami are v i s c e r a l components o f t h e  n e r v e s , which a r e f u n c t i o n a l l y system.  rami.  out-  related  spinal  to t h e s y m p a t h e t i c  The components o f the s p i n a l n e r v e c o n t a i n e d i n tthe  communicating  r a m i a r e u s u a l l y m y e l i n a t e d and c o n s t i t u t e  w h i t e r a m i communicantes.  The m a j o r i t y o f the s y m p a t h e t i c  components a r e non-medullated o r o n l y s l i g h t l y so, and constitute  the g r a y r a m i communicantes.  contain both v i s c e r a l a f f e r e n t efferent  the  they  The w h i t e r a m i  and p r e g a n g l i o n i c  visceral  f i b r e s , whereas the g r a y rami a r e composed o f  postganglionic fibres.  The d i s t r i b u t i o n o f the w h i t e r a m i  i s l i m i t e d t o a few s p i n a l n e r v e s whereas the g r a y r a m i a r e a s s o c i a t e d w i t h every s p i n a l nerve ( P i g . 5 ) .  Function; The maintenance  o f the i n t e r n a l environment  s t e a d y o r normal s t a t e i s brought about t h r o u g h the action  o f the autonomic nervous system.  in a regulating  The s t e a d y s t a t e  the body i s spoken o f by Cannon (1937) as h o m e o s t a s i s . refers  t o the autonomic n e r v e s as the i n t e r o f e c t i v e  because t h r o u g h t h e i r a c t i o n  they m a i n t a i n t he  of He  system,  homeostasis  - 14 o f t h e body, c o n s e q u e n t l y he speaks o f t h e v o l u n t a r y  nervous  system as t h e e x t e r o f e c t i v e system, s i n c e t h r o u g h i t s e x t e r o ceptors  and e f f e c t o r s , i t e s t a b l i s h e s a d i r e c t r e l a t i o n s h i p  w i t h the external The  environment.  e f f e c t s produced by s t i m u l a t i o n o f t h e s y m p a t h e t i c  and p a r a s y m p a t h e t i c a r e a n t a g o n i s t i c .  Thus s t i m u l a t i o n o f  the vagus i n h i b i t s t h e a c t i o n o f t h e h e a r t whereas s t i m u l a t i o n o f t h e s y m p a t h e t i c augments t h e a c t i o n o f t h e h e a r t .  Selachian  System  I n f i s h t h e autonomic i n n e r v a t i o n i s n o t d i f f e r e n t i a t e d i n t o f u n c t i o n a l l y a n t a g o n i s t i c sympathetic and p a r a s y m p a t h e t i c systems.  The autonomic system o f s e l a c h i a n s  i s composed o f  a d i f f u s e s y m p a t h e t i c system and a c r a n i a l o u t f l o w .  The  vagus s u p p l i e s f i b r e s t o t h e a n t e r i o r v i s c e r a down t o the p y l o r i c stomach and t h e s y m p a t h e t i c i n n e r v a t e s viscera.  the p o s t e r i o r  Thus t h e r e i s o n l y one s t r u c t u r e , namely the p y l o r i c  stomach w h i c h r e c e i v e s f i b r e s from two s o u r c e s .  Young (1933)  w o r k i n g on S c y l l i u m found t h a t v a g a l s t i m u l a t i o n i n h i b i t s t h e movement o f t h e p y l o r u s and t h a t s y m p a t h e t i c s t i m u l a t i o n increases  i t s movement.  The s a c r a l autonomic i s l a c k i n g i n  s e l a c h i a n s , as i t i s i n t e l e o s t s b u t L a n g l e y * a n d O r b e l l i (1933) have d i s c o v e r e d The  i t s existence  i n some e a r l y  tetrapods.  d i f f e r e n t i a t i o n i n t o two f u n c t i o n a l l y a n t a g o n i s t i c  - 15 -  systems i s a r e c e n t The  development.  s y m p a t h e t i c system i s e s s e n t i a l l y segmental,  a l t h o u g h not every segment p o s s e s s e s a d e f i n i t e number of ganglia.  The number o f g a n g l i a p e r segment may  one t o t h r e e . by m e d u l l a t e d The  v a r y from  The g a n g l i a a r e connected to the s p i n a l n e r v e s p r e g a n g l i o n i c f i b r e s , the rami communicantes.  r e c u r r e n t g r a y r a m i communicantes a r e l a c k i n g i n  selachians  (Young, 1933).  The most a n t e r i o r g a n g l i o n of importance i s t h e g a s t r i c ganglion, which i s i n c l o s e a s s o c i a t i o n w i t h a x i l l a r y body.  The  the  a n t e r i o r rami a r i s e from s p i n a l n e r v e s  above the pharynx to pass p o s t e r i o r l y to e n t e r the  axillary  body.  postgang-  Synapsis occurs  i n t h e g a s t r i c g a n g l i o n : and  l i o n i c f i b r e s p a s s p o s t e r i o r l y , accompanying t h e c o e l i a c a r t e r y t o the v i s c e r a .  The  sympathetic g a n g l i a l y i n g behind  the g a s t r i c g a n g l i a are s m a l l and  are s i t u a t e d i n the d o r s a l  w a l l o f the p o s t e r i o r c a r d i n a l s i n u s .  In the k i d n e y  the g a n g l i a a r e a l w a y s v e r y c l o s e l y a s s o c i a t e d w i t h  region the  s u p r a r e n a l b o d i e s ; whereas i n t h e a n t e r i o r end t h e y a r e usually  separated. The  suprarenals  i n the k i d n e y r e g i o n a r e embedded  i n the d o r s a l p a r t o f the mesonephros.  Young (1933) found  t h a t t h e r e i s a d i f f e r e n c e i n the s u p r a r e n a l s sexes.  i n the  two  The males o f S c y l l i u m have v e r y l a r g e masses o f  s u p r a r e n a l t i s s u e and occupy a c o n s i d e r a b l e p a r t of  the  - 16 -  volume o f the k i d n e y whereas i n females the amount o f r e n a l t i s s u e i s decreased.  supra-  The amount o f a d r e n a l i n s e c r e t e d  i n males and females i s the same; t h e r e f o r e does n o t depend on the volume o f t i s s u e p r e s e n t .  The  suprarenals  are  e v i d e n t l y homologous t o the a d r e n a l c o r t e x o f h i g h e r v e r t e brates . There a r e no autonomic f i b r e s i n the t a i l r e g i o n o f selachians.  The l a s t few g a n g l i a i n t h e c a u d a l r e g i o n a r e  v e r y s m a l l and the s e r i e s t e r m i n a t e s a t the same p o s i t i o n as the  kidney.  M a t e r i a l s and Method  Specimens o f Hydrolagus c o l l i e i were o b t a i n e d f r o m bottom t r a w l e r s o p e r a t i n g i n t h e G u l f o f G e o r g i a , o f f P o i n t Grey and o f f P o i n t A t k i n s o n .  The a d u l t s a t t a i n i n g l e n g t h s  up to t h r e e f e e t a r e u s u a l l y f o u n d a t depths below t h i r t y fathoms.  The young a r e s m a l l r e p l i c a s o f t h e a d u l t s ; and  the h i s t o l o g i c a l s t u d i e s o f t h i s paper were conducted on young specimens, f i v e t o s i x i n c h e s i n l e n g t h . d i f f i c u l t y was  encountered i n o b t a i n i n g l i v e  Great  specimens,  because o f the change i n p r e s s u r e , when they were'brought to the s u r f a c e .  The abdominal w a l l s o f the young'specimens  were s l i t open and p r e s e r v e d i n the f o l l o w i n g f i x a t i v e s : 10$ n e u t r a l f o r m o l , Bouin's f l u i d , W i e s s e l ' s f l u i d ,  and  - 17  ammoniated 10%  alcohol.  F r e s h specimens and  s e r v e d specimens were d i s s e c t e d t r a c e d out,  -  and  formalin  the course o f the n e r v e s  e i t h e r by the naked eye o r under the  microscope.  pre-  binocular  B l a c k e n i n g the n e r v e s w i t h a 1% s o l u t i o n  of  osmium t e t r o x i d e f a c i l i t a t e s o b s e r v a t i o n g r e a t l y . Nelson's m o d i f i c a t i o n  o f S i h l e r ' s method f o r s t a i n i n g  n e r v o u s t i s s u e " i n t o t o " was  employed f o r m a c r o s c o p i c  o b s e r v a t i o n s (Guyer, 1936).  Three s o l u t i o n s a r e  required:  1. Potassium hydroxide  \% aqueous s o l u t i o n 2.  Glacial acetic acid Glycerine C h l o r a l h y d r a t e 1% s o l u t i o n  1 1 6  part part parts  1 1 6  part part parts  3. Glycerine E h r l i c h ' s acid hematoxylin C h l o r a l h y d r a t e 1% s o l u t i o n The  a l c o h o l p r e s e r v e d specimens were t r a n s f e r e d  solution 1 for 1 - 3  days.  The  p o t a s s i u m h y d r o x i d e has  m a c e r a t i n g e f f e c t upon t h e t i s s u e s ; t h e r e f o r e was  the  then d e s t a i n e d i n s o l u t i o n 2 f o r 18 h o u r s and  in glycerine.  When  specimens were p l a c e d I n t o s o l u t i o n 2 f o r  a p p r o x i m a t e l y 72 h o u r s , then i n t o s o l u t i o n 3 f o r 3 - 7 I t was  a  material  checked f r e q u e n t l y t o p r e v e n t complete m a c e r a t i o n .  t r a n s p a r e n t the  to  The  nervous t i s s u e was  days. cleared  colored dark purple  - 18 -  and the s u r r o u n d i n g t i s s u e s were s e m i - t r a n s p a r e n t . I f the specimens a r e l a r g e and o l d i t i s d i f f i c u l t to r e n d e r the m u s c u l a t u r e  t r a n s p a r e n t ; the s u r r o u n d i n g  can be e a s i l y p i c k e d away w i t h f o r c e p ^ s ^ a n d ) t h u s  tissue  exposjfPthe  dark p u r p l e n e r v e s . In s t u d y i n g the micro-anatomy, t h e f o l l o w i n g s t a i n s and p r o c e d u r e s were employed: (a) Hematoxylin  and E o s i n :  A standard p r e p a r a t i o n of H a r r i s  1  hematoxylin  was  used and a s a t u r a t e d s o l u t i o n o f e o s i n i n 90% alcohol<w53P as a c o u n t e r  stain.  (b) Bodian's A c t i v a t e d P r o t a r g o l (1937): Remove the wax distilled  i n x y l o l and r u n t h e s l i d e s down to  water.  Impregnate the s e c t i o n s w i t h a 1% s o l u t i o n o f p r o t a r g o l ( s i l v e r albumose) c o n t a i n i n g 5 grams o f m e t a l l i c copper p e r 100 c c . o f s o l u t i o n .  The copper s h o u l d be  cleaned  w i t h soap and water to remove any i m p u r i t i e s on the s u r f a c e . Leave i n t h i s s o l u t i o n 12 t o 48 h o u r s a t 37°C. d i s t i l l e d water.  Wash I n  The p r o t a r g o l - c o p p e r s o l u t i o n can o n l y be  used once. Reduce f o r 3 m i n u t e s I n the f o l l o w i n g  solution:  Hydroquinone - 1 gram Sodium s u l p h i t e ( c r y s t a l s ) - 10 grams D i s t i l l e d water - 100 c c . Wash t h o r o u g h l y i n r u n n i n g t a p water ( a t l e a s t 3 m i n u t e s ) and then r i n s e i n d i s t i l l e d  water.  - 19 -  Tone i n a 0.2% s o l u t i o n o f g o l d c h l o r i d e o r u n t i l s e c t i o n s have become d e c o l o r i z e d , Place sections  rinse i n d i s t i l l e d  water.  i n a 2*0% s o l u t i o n o f o x a l i c a c i d  u n t i l t h e s e c t i o n s become p u r p l e . R i n s e i n two changes o f d i s t i l l e d  Check under t h e m i c r o s c o p e . water.  Remove t h e r e s i d u a l s i l v e r s a l t s i n a s o l u t i o n o f 5% sodium t h i o s u l p h a t e  f o r 5 minutes.  Wash f o r 10 minutes i n r u n n i n g t a p w a t e r , d e h y d r a t e and mount i n balsam. The n e r v e f i b r e s and n e r v e c e l l s s h o u l d be a maroon or dark blue c o l o r . (c) Holmes' S i l v e r I m p r e g n a t i o n (1943): Remove p a r a f f i n i n x y l o l and b r i n g s l i d e s t o d i s t i l l e d water.  ,  P l a c e s l i d e s i n 20% s i l v e r n i t r a t e i n t h e d a r k a t room temperature, f o r 1 t o 1§ h o u r s . i n 3 changes o f d i s t i l l e d  Wash f o r 10 minutes  water.  P l a c e s l i d e s i n t h e i m p r e g n a t i n g s o l u t i o n , made up as f o l l o w s : mix 55 c c . o f s o l u t i o n A, b o r i c a c i d , and 45 c c . o f s o l u t i o n B, b o r a t e .  Add a p p r o x i m a t e l y 300 c c . o f  d i s t i l l e d w a t e r and e x a c t l y 1 c c . o f a 1% s o l u t i o n o f s i l v e r n i t r a t e and 5 c c . o f a 10$ aqueous s o l u t i o n o f pure  pyridine.  Make up t o 500 c c . P l a c e s l i d e s i n t h e Impregnating s o l u t i o n In t h e dark a t 37°C. f o r about 24 h o u r s .  A t t h e end o f 2 - 3  hours l i f t t h e s l i d e s o u t o f the s o l u t i o n t o break any a i r b u b b l e s t h a t may have formed on t h e s e c t i o n s . s h o u l d t u r n brown.  The  sections  - 20 -  B u f f e r A. Boric a c i d ( a n a l y t i c a l reagent) D i s t i l l e d water  - 12.4 gms. - 1000 c c .  B u f f e r B. B o r a t e (NaBo.lOH 0 a n a l y t i c a l r e a g e n t ) - 19 gms. D i s t i l l e d water - 1000 c c . P l a c e s l i d e s f o r 3 minutes i n t h e f o l l o w i n g r e d u c e r : Hydroquinone Sodium s u l p h i t e ( c r y s t a l s ) D i s t i l l e d water  - 1 gm. - 10 gm. - 1000 c c .  Wash I n r u n n i n g t a p w a t e r a t l e a s t 3 m i n u t e s . in distilled  Rinse  water.  P l a c e i n a 0.2$ s o l u t i o n o f g o l d c h l o r i d e f o r 3 minutes o r u n t i l s e c t i o n s become d e c o l o r i z e d . distilled  Rinse i n  water.  P l a c e i n a 2% s o l u t i o n o f o x a l i c a c i d f o r 3 t o 10 minutes.  The s e c t i o n s  Rinse i n d i s t i l l e d  turn purple.  Check under m i c r o s c o p e .  water.  P l a c e I n a b% s o l u t i o n o f sodium h y p o s u l p h i t e f o r 5 minutes.  Wash i n r u n n i n g t a p w a t e r f o r a t l e a s t 10  minutes. Dehydrate and mount i n balsam, (d) M a l l o r y ' s  Triple Stain:  Remove p a r a f f i n and b r i n g s l i d e s t o d i s t i l l e d Mordant t h e s e c t i o n s  i n a saturated  solution of  HgClg i n water p l u s 5% a c e t i c a c i d f o r 10 m i n u t e s . in d i s t i l l e d  water.  Rinse  water.  P l a c e s l i d e s I n a 0.5$ s o l u t i o n o f a c i d f u c h s i n i n d i s t i l l e d w a t e r f o r 15 t o 20 seconds.  Differentiate  sections  - 21 -  i n d i s t i l l e d water. the  Do n o t c a r r y o v e r any a c i d f u c h s i n i n t o  next s o l u t i o n . P l a c e i n a \% s o l u t i o n o f phosphomolybdic  for  1 minute.  Avoid contact w i t h metal forceps.  acid  Wash I n  d i s t i l l e d water. P l a c e f o r 75 seconds i n M a l l o r y ' s s t a i n w h i c h i s of  the f o l l o w i n g composition: A n i l i n e Blue Orange G Oxalic acid D i s t i l l e d water  -  0.5 gms. 2 " 2 " 200 c c .  Wash s l i d e s t h o r o u g h l y i n d i s t i l l e d w a t e r . D i f f e r e n t i a t e a n i l i n e b l u e i n 90$ a l c o h o l , f o r about 10 seconds. Dehydrate r a p i d l y i n 2 changes o f a b s o l u t e a l c o h o l and mount i n balsam. N u c l e i a r e r e d ; muscle and v a r i o u s c y t o p l a s m i c c o n s t i t u e n t s a r e r e d t o orange; nervous system i s l i l a c ; c o l l a g e n i s dark b l u e ; mucous, c o n n e c t i v e t i s s u e and o t h e r h y a l i n e substances a r e b l u e .  - 22 -  C r a n i a l Autonomic Nervous  System  The c r a n i a l autonomic system o f H y d r o l a g u s c o l l i e i I v e r y much reduced from t h e c o n d i t i o n met w i t h i n h i g h e r vertebrates.  A t t h e same time, t h e c o n d i t i o n i s f a r s i m p l e r  than t h a t found I n t h e s e l a c h i a n s o r t e l e o s t s . f i b r e s a r e f o u n d i n the I l l r d , V l l t h ,  Autonomic  I X t h and X t h c r a n i a l  nerves. The I l l r d c r a n i a l n e r v e i s t h e most a n t e r i o r n e r v e to g i v e r i s e t o autonomic f i b r e s .  The motor f i b r e s pass o u t  through t h e v e n t r a l r o o t and a f i n e b r a n c h p a s s e s o u t toward the c i l i a r y g a n g l i o n .  The p r e g a n g l i o n i c f i b r e s synapse i n  the c i l i a r y g a n g l i o n and p o s t g a n g l i o n i c f i b r e s l e a v e by two p a t h s t o i n n e r v a t e t h e eye. T h i s i s t h e o n l y v e n t r a l outflow o f the parasympathetic d i v i s i o n .  The s a c r a l  autonomic o u t f l o w o f t h e h i g h e r v e r t e b r a t e s i s t h r o u g h t h e v e n t r a l r o o t s ; however Hydrblagus c o l l i e i l a c k s a s a c r a l o u t f l o w , as do a l l f i s h . The V l l t h c r a n i a l n e r v e a r i s e s from the l a t e r a l a s p e c t o f t h e m e d u l l a by t h r e e main r o o t s .  There a r e seven  d i s t i n c t branches o r i g i n a t i n g from t h i s n e r v e ; however o n l y two o f t h e s e b r a n c h e s , t h e chorda tympani and t h e p a l a t i n e , are c l a s s e d as autonomic i n f u n c t i o n .  The chorda tympani  i n n e r v a t e s t h e s i d e s and f l o o r o f t h e mouth and t h e p a l a t i n e i n n e r v a t e s t h e r o o f o f t h e mouth.  - 23 -  The I X t h c r a n i a l n e r v e emerges from t h e s k u l l t h r o u g h a s i n g l e foramen. the  I t appears t o a r i s e as a s i n g l e r o o t from  medulla, immediately a n t e r i o r to the f i r s t root o f the  vagus.  I t forms i n t o a g a n g l i o n Immediately o u t s i d e t h e  cranium and a b r a n c h proceeds from t h e g a n g l i o n t o t h e f i r s t gill  cleft. The vagus o r X t h c r a n i a l n e r v e i s i n a v e r y p r i m i t i v e  condition.  I t s o r i g i n from t h e m e d u l l a i s by s i x r o o t s o f  varying size.  They pass t h r o u g h t h e cranium by f o u r  foramena  and i m m e d i a t e l y on emerging s w e l l i n t o f o u r s e p a r a t e g a n g l i a . The f i r s t two g a n g l i a have many b r a n c h e s coming o f f . The most i m p o r t a n t b r a n c h i s t h e l a t e r a l l i n e b r a n c h w h i c h i s made up o f f i b r e s from b o t h v a g a l g a n g l i a one and two; t h e m a j o r i t y o f t h e f i b r e s coming from g a n g l i o n two. The f i r s t v a g a l g a n g l i o n sends f i b r e s t o a g l a n d w h i c h i s l o c a t e d i n the  d o r s a l w a l l o f t h e pharynx  (Pig. 4).  The s t r u c t u r e o f  t h i s g l a n d was n o t d e t e r m i n e d ; presumably i t i s a mucous gland.  F i g u r e f i v e shows t h e o r i g i n o f t h e second v a g a l  g a n g l i o n from t h e m e d u l l a by two r o o t s emerging t h r o u g h t h e same foramen.  The t h i r d V a g a l g a n g l i o n a r i s e s from t h e  m e d u l l a by t h e f o u r t h r o o t .  This ganglion i s situated  s l i g h t l y v e n t r a l t o t h e second g a n g l i o n , and i n a l a t e r a l view i t o b s c u r e s t h e l a t e r a l l i n e b r a n c h w h i c h runs between i t and the  cranium ( F i g . 5 ) .  The main b r a n c h o f t h e f o u r t h g a n g l i o n  i s the i n t e s t i n a l branch.  Each o f t h e g a n g l i a sends a b r a n c h  to one o f t h e v i s c e r a l pouches.  Nerve c e l l s p e r s i s t f o r a  - 24  -  c o n s i d e r a b l e d i s t a n c e p o s t e r i o r l y i n b o t h the l a t e r a l the i n t e s t i n a l b r a n c h ( P i g . 6 ) .  b r a n c h and  can be seen the d i f f e r e n c e ganglia.  The  i n the  I n the same F i g u r e  second and  second g a n g l i o n has  line  fourth  l a r g e c e l l s and  vagal  the  spacing  between the c e l l s i s g r e a t , whereas i n the f o u r t h ' g a n g l i o n the c e l l s a r e  s m a l l and  compact.  The  c e l l s o f the  lateral  l i n e g a n g l i o n p e r s i s t f a r t h e r p o s t e r i o r l y t h a n do'any o f other vagal ganglia.  F i g u r e seven shows the  o f v a g a l g a n g l i o n number two  portion  e x t e n d i n g as f a r p o s t e r i o r l y  the o r i g i n o f the f i r s t s p i n a l n e r v e . between the l a t e r a l l i n e n e r v e and The  terminal  the  The  s p i n a l n e r v e s pass  the v i s c e r a l vagus.  l a t e r a l l i n e n e r v e remains i n a p p r o x i m a t e l y  same p o s i t i o n throughout i t s e n t i r e l e n g t h . r e g i o n i t remains l a t e r a l to the  as  In the  the  anterior  s p i n a l c o r d ; i n the  kidney  r e g i o n i t assumes a p o s i t i o n between the k i d n e y and  the  n o t o c h o r d ; i n the t a i l r e g i o n i t i s l a t e r a l to the  caudal  artery. The distance,  v i s c e r a l vagus c o u r s e s p o s t e r i o r l y f o r a s h o r t  then l a t e r a l l y ( F i g . 8 ) , to assume a p o s i t i o n  t o the pharynx.  The  pharynx a t t h i s p o i n t , has  c h a r a c t e r i s t i c U-shaped p o s i t i o n , and  assumed a  the v i s c e r a l vagus i s  s i t u a t e d on the d o r s a l arms o f the U-shaped pharynx. divides and  i n t o s e v e r a l b r a n c h e s ; the c a r d i a c ,  a ramus to the g a s t r i c g a n g l i o n by way  g a n g l i o n , the p r e g a s t r i c  ganglion.  close  the of a  It  intestinal diffuse  This pregastric  ganglion  i s a s y m p a t h e t i c g a n g l i o n s i t u a t e d on a b r a n c h w h i c h a r i s e s  from  - 25  the g a s t r i c g a n g l i o n , and The  -  proceeds a n t e r i o r l y .  m a j o r i t y o f the f i b r e s of the v i s c e r a l vagus  form a complex network o v e r the oesophagus and intestine.  The  anterior  main n e r v e bundles run p o s t e r i o r l y  a t e l y under the pigmented coat of the  immedi-  s e r o s a ; from t h i s  p o s i t i o n f i b r e s pass t o the m u s c u l a r i s mucosa ( P i g . 9 ) . c a r d i a c b r a n c h comes o f f a n t e r i o r and  p a s s e s a l o n g the v e n t r a l  the  s i n u s venosus.  a few  o f the  to the p r e g a s t r i c  p a s s t o the  ventricles;  auricles.  S i n c e c r a n i a l n e r v e s I I I , V I I and are  ganglion  s u r f a c e of the oesophagus to  There a r e no f i b r e s to the  f i b r e s may  The  IX of t h i s s p e c i e s  i d e n t i c a l to those i n S e l a c h i i , the autonomic components 1  o f t h e s e n e r v e s were assumed to be Selachii. dissected  The out  actual  s i m i l a r to those i n  course o f the n e r v e s were, however,  i n H y d r o l a g u s . ( L i t t l e 1932,  (Neal & Rand 1939).  Sympathetic System  The and  fibres situated  cavity. per  s y m p a t h e t i c system i s a d i f f u s e network o f  The  i n the  ganglia are  segment and  cells  d o r s a l w a l l o f the abdominal  a r r a n g e d s e g m e n t a l l y but  the p o s i t i o n  segment may  segment, but  vary.  There  are g e n e r a l l y  two  have o n l y one  g a n g l i o n , whereas some have t h r e e d i s t i n c t  ganglia.  g a n g l i a and  The  g a n g l i a per  i n the  the number  some segments  f i b r e s are f o r m e d i n t o two  t r u n k s , l y i n g v e n t r o - l a t e r a l l y on  e i t h e r s i d e o f the  diffuse spinal  - 26 -  cord.  The g a n g l i a o f a d j a c e n t segments a r e c o n n e c t e d by-  l o n g i t u d i n a l rami o r c o n n e c t i v e s .  These c o n n e c t i v e s a r e n o t  r e s o l v e d i n t o a d e f i n i t e , u n i f i e d trunk, but r a t h e r c o n s i s t o f a number o f f i b r e s p a s s i n g s e p a r a t e l y between a d j a c e n t ganglia.  Transverse  c o n n e c t i v e s e x i s t , b u t they a r e fewer  i n number than the l o n g i t u d i n a l c o n n e c t i v e s .  A transverse  c o n n e c t i v e l e a v i n g a g a n g l i o n on one s i d e o f t h e s p i n a l c o r d does n o t n e c e s s a r i l y p a s s t o t h e n e a r e s t g a n g l i o n on t h e o p p o s i t e s i d e , but can pass t o a g a n g l i o n s i t u a t e d s e v e r a l segments p o s t e r i o r l y . A n t e r i o r Abdominal Region. The g a s t r i c g a n g l i o n i s t h e l a r g e s t and most i m p o r t a n t g a n g l i o n i n the a n t e r i o r abdominal r e g i o n . a t e d w i t h t h e g a s t r i c g a n g l i o n i s a mass o f s u p r a r e n a l and t o g e t h e r they c o n s t i t u t e t h e " a x i l l a r y " body.  Associtissue  This i s  the l a r g e s t c o l l e c t i o n o f s u p r a r e n a l t i s s u e i n the body.  The  a x i l l a r y body l i e s i n the p o s t e r i o r c a r d i n a l s i n u s , s u r r o u n d i n g the s u b c l a v i a n a r t e r y .  The c e l l s o f t h e g a s t r i c  g a n g l i o n a r e i n t e r s p e r s e d throughout t h e s u p r a r e n a l t i s s u e and the p o s t g a n g l i o n i c f i b r e s from t h e sympathetic  c e l l s pass  d i r e c t l y t o t h e c e l l s o f t h e s u p r a r e n a l body.  I n the d o r s a l  w a l l o f t h e p o s t e r i o r c a r d i n a l s i n u s , Immediately d o r s a l t o the a x i l l a r y b o d i e s , r u n t h e s p i n a l n e r v e s ;  communicating  rami pass from the a x i l l a r y body t o the s p i n a l n e r v e s (Pig.  10).  The a n t e r i o r p o r t i o n o f t h e l i v e r a l m o s t  completely  - 27 -  surrounds the oesophagus and i s connected to i t by a f i n e mesentery p a s s i n g from t h e l a t e r a l w a l l o f t h e oesophagus t o the d o r s a l p a r t o f the l i v e r .  The s y m p a t h e t i c f i b r e s p a s s i n g  down the l a t e r a l w a l l o f the oesophagus d i v i d e s e n d i n g a b r a n c h t o the l i v e r by way o f the c o n n e c t i n g mesentery. The s u b c l a v i a n a r t e r y p a s s e s t h r o u g h the a x i l l a r y body i n i t s l a t e r a l c o u r s e ; i t then proceeds p o s t e r i o r l y and v e n t r a l l y , r e c e i v i n g vaso-motor f i b r e s from the s p i n a l nerves ( F i g . 11). There a r e many f i b r e s r a d i a t i n g out from t h e a x i l l a r y body; however t h e r e appear t o be f o u r major pathways l e a v i n g the g a n g l i o n .  The f i r s t group f o r m the l o n g i t u d i n a l  c o n n e c t i v e s between the g a s t r i c g a n g l i o n and the p r e g a s t r i c ganglion.  T h i s group c o n t a i n s the ramus between the vagus  and the s y m p a t h e t i c .  From the p r e g a s t r i c g a n g l i a , rami  communicantes pass t o t h e s p i n a l n e r v e s .  A n o t h e r group o f  f i b r e s c o u r s e a n t e r i o r l y t o t h e r e g i o n o f the v e n t r a l a o r t a . The t h i r d group o f f i b r e s pass p o s t e r i o r l y as l o o s e s t r a n d s to make c o n n e c t i o n w i t h o t h e r s y m p a t h e t i c g a n g l i a or as vaso-motor f i b r e s s u p p l y i n g b l o o d v e s s e l s .  The r e m a i n i n g  major b r a n c h from the g a s t r i c g a n g l i o n p a s s e s m e d i a l l y t o meet the b r a n c h f r o m t h e g a s t r i c g a n g l i o n of t h e o p p o s i t e s i d e to form t h e s p l a n c h n i c n e r v e ( F i g . 1 2 ) .  The u n i o n o f  the branches from the g a s t r i c g a n g l i o n o c c u r s a t t h e p o i n t where t h e c o e l i a c a r t e r y comes o f f the d o r s a l a o r t a ( F i g . 1 3 ) . The s p l a n c h n i c n e r v e accompanies  the c o e l i a c a r t e r y p o s t e r i o r l y  - 28 -  to i n n e r v a t e t h e i n t e s t i n e ( P i g . 1 4 ) , l i v e r , g a l l b l a d d e r , s p l e e n , and p a n c r e a s . Between t h e g a s t r i c g a n g l i o n and t h e k i d n e y t h e r e o c c u r t h r e e p a i r s o f s m a l l g a n g l i a surrounded by a s m a l l amount o f s u p r a r e n a l t i s s u e ( P i g . 1 5 ) . The g a n g l i a l i e i n the p o s t e r i o r c a r d i n a l s i n u s , e i t h e r i n t h e d o r s a l w a l l (Pig.  1 5 ) , o r i n t h e l a t e r a l w a l l ( P i g . 1 6 ) . I n some o f t h e  g a n g l i a o c c u r r i n g i n t h e a n t e r i o r r e g i o n t h e r e I s no s u p r a r e n a l t i s s u e surrounding the ganglion c e l l s  (Pig. 18).  Commencing a t t h e b r a c h i a l p l e x u s and p a s s i n g p o s t e r i o r l y , t h e r e a r e a p p r o x i m a t e l y twenty s p i n a l r a d i a t i n g l a t e r a l l y from t h e s p i n a l c o r d .  nerves  The a x i l l a r y body  l i e s immediately v e n t r a l to the b r a c h i a l plexus.  The a n t e r i o r  t i p o f the kidney i s s i t u a t e d a t the l e v e l of the f i f t h s p i n a l n e r v e and t h e gonads a r e s l i g h t l y p o s t e r i o r .  In the  male t h e vasa e f f e r e n t i a a r e a mass o f c o i l e d t u b u l e s and f o l d around t h e a n t e r i o r t i p o f t h e k i d n e y b e f o r e they pass to t h e vasa d e f e r e n t i a .  The i n n e r v a t i o n o f t h e s e s t r u c t u r e s  i s p a r t l y d e r i v e d from t h e g a s t r i c g a n g l i o n and p a r t l y  from  the s y m p a t h e t i c g a n g l i a a s s o c i a t e d w i t h t h e a n t e r i o r p o r t i o n of t h e k i d n e y .  F i b r e s c a n be seen l e a v i n g t h e a x i l l a r y body  and c o u r s i n g p o s t e r i o r l y to t h e k i d n e y and gonads.  These  f i b r e s i n t u r n make c o n n e c t i o n s w i t h t h e s y m p a t h e t i c g a n g l i a of t h e k i d n e y .  - 29  -  P o s t e r i o r Abdominal R e g i o n . The  f i r s t s y m p a t h e t i c g a n g l i a to appear a s s o c i a t e d  w i t h the k i d n e y l i e between the d o r s a l a o r t a and the  kidney  ( P i g . 17).  small  They a r e s m a l l g a n g l i a w i t h a r e l a t i v e l y  amount o f a s s o c i a t e d s u p r a r e n a l  tissue.  The  succeeding  g a n g l i a v a r y i n s i z e , as does the amount o f s u p r a r e n a l a s s o c i a t e d w i t h them.  The  tissue  g e n e r a l l o c a t i o n o f the g a n g l i a  i s between the d o r s a l a o r t a and  the k i d n e y , but t h e y a r e  o f t e n found i n a p o s i t i o n t h a t i s l a t e r a l t o the a o r t a d o r s a l t o the kidney The  and  (Pig. 24).  suprarenal  t i s s u e may  be e i t h e r s c a t t e r e d among  the c e l l s o f the s y m p a t h e t i c g a n g l i a o r may  o c c u r as a  s e p a r a t e mass o f t i s s u e a p a r t from t h e g a n g l i a . s y m p a t h e t i c g a n g l i o n i s u s u a l l y a s p h e r i c a l body,  The appearing  m a c r o s c o p i c a l l y as a n o d u l e among the network o f n e r v e f i b r e s . The  shape of the s u p r a r e n a l b o d i e s i s i r r e g u l a r . I n the male the M u l l e r i a n ducts p e r s i s t unchanged  from t h e f e m a l e c o n d i t i o n , p a s s i n g between the t e s t i s and sperm d u c t , f r o m a p o s i t i o n s l i g h t l y a n t e r i o r t o the  the  kidney,  to t h e i r b l i n d ending i n t h e w a l l o f the u r o g e n i t a l s i n u s . The  vas d e f e r e n s passes i n t o the s e m i n a l v e s i c l e a t approx-  i m a t e l y the t e n t h s p i n a l n e r v e .  Nerve f i b r e s r a m i f y o v e r  s u r f a c e o f the seminal v e s i c l e , e s p e c i a l l y t h e p o s t e r i o r p o r t i o n , and  s e v e r a l s m a l l g a n g l i a can be seen s c a t t e r e d  among the p a t h s o f the  nerves.  the  - 30 -  I n females t h e k i d n e y does n o t extend as f a r a n t e r i o r l y a s i t does i n t h e male. meet a n t e r i o r l y a l o n g  The M u l l e r i a n d u c t s o r o v i d u c t s ,  the midline  o f t h e body and p o s s e s s a  common opening i n t o t h e body c a v i t y . a n t e r i o r part o f the kidney, g l o b u l a r s h e l l glands.  A t the l e v e l o f t h e  the oviduct s w e l l s i n t o l a r g e  Further p o s t e r i o r l y i t again  i n t o the u t e r i n e p o r t i o n of the oviduct.  swells  The o v a r i e s i n t h e  a d u l t female l i e between t h e two o v i d u c t s a n t e r i o r t o the s h e l l g l a n d , b u t i n t h e immature specimen they a r e suspended i n a mesentery l a t e r a l t o t h e o v i d u c t s .  The i n n e r v a t i o n o f  these s t r u c t u r e s i s p r i m a r i l y d e r i v e d from the 'sympathetic g a n g l i a , a s s o c i a t e d w i t h the kidney.  Nerve f i b r e s c a n be  seen t o r u n over t h e s u r f a c e o f t h e o v i d u c t , e s p e c i a l l y t h e uterine portion. Suprarenal  Tissue.  The cavity.  suprarenal  t i s s u e i s l i m i t e d t o t h e abdominal  I t o c c u r s as i r r e g u l a r l y shaped b o d i e s g e n e r a l l y i n  c l o s e a s s o c i a t i o n w i t h the sympathetic g a n g l i a .  The supra-  r e n a l bodies a r e often r e f e r r e d to as the chromaffin because i n s p e c i a l p r e p a r a t i o n s a f f i n i t y f o r chromium s a l t s .  t h e c e l l s show a g r e a t  The r e a c t i o n t h a t t a k e s  I s t h e chrome r e a c t i o n (Addison 1 9 2 7 ) , ( L i s o n 1948).  1936),  Many a u t h o r s a r e a t v a r i a n c e w i t h r e g a r d  s p e c i f i c i t y o f t h e chrome r e a c t i o n .  place  (Lillle  to the  Some s a y t h a t i t i s a  t e s t o f t h e t o t a l amount o f c h r o m a f f i n whereas o t h e r s  bodies,  tissue  present,  s t a t e t h a t t h e chrome r e a c t i o n i s o n l y i  - 31 -  s p e c i f i c f o r the s e c r e t i o n p r o d u c t of the t i s s u e (Arey 1934), ( C o l e 1941), (Hyman 1942). two  Young (1933),  s t a t e s t h a t i n the  sexes o f the d o g f i s h t h e r e a r e v a r y i n g amounts of  chromaffin  t i s s u e present.  as much c h r o m a f f i n  The males p o s s e s s n e a r l y  t i s s u e as the f e m a l e s .  twice  Assuming t h a t  the  chrome r e a c t i o n i s an i n d i c a t i o n o f the t o t a l amount o f s e c r e t i o n , the r e s u l t s show t h a t the amount of s e c r e t i o n i s the same i n b o t h s e x e s . r e n a l t i s s u e present  I n Hydrolagus the amount o f  supra-  d i f f e r s , b u t not as g r e a t l y as i n the  dogfish. The fusiform.  c e l l s o f the c h r o m a f f i n b o d i e s a r e p o l y h e d r a l The  or  c y t o p l a s m i n r o u t i n e p r e p a r a t i o n s , appears to  c o n t a i n many b a s o p h i l i c g r a n u l e s l a r g e s t mass o f c h r o m a f f i n w i t h the g a s t r i c g a n g l i o n  ( K e n d a l l 1947).  t i s s u e i n the body i s a s s o c i a t e d ( F i g . 1 9 ) ; the r e m a i n i n g  have v a r y i n g amounts of t i s s u e p r e s e n t . sympathetic g a n g l i a are approximately the c h r o m a f f i n c e l l s  The  The  ganglia  c e l l s of  the  f o u r times the s i z e o f  ( F i g . 2 0 ) , ( F i g . 21).  Interrenal Tissue. The a n t e r i o r t w o - t h i r d s o f the k i d n e y i s p a i r e d has a segmental appearance; i t t h e n f u s e s i n t o one  and  un*seg-  mented body, p r o j e c t i n g p o s t e r i o r l y i n t o a p o s t - a b d o m i n a l pocket.  A s h o r t d i s t a n c e p o s t e r i o r to the p o i n t o f f u s i o n  of the k i d n e y ,  appears the i n t e r r e n a l t i s s u e , l y i n g a l o n g  l i n e of f u s i o n ( F i g . 22).  The  i s therefore approximately  a t the e i g h t e e n t h  the  a n t e r i o r l i m i t o f the i n t e r r e n a l s p i n a l nerve.  - 32 I t extends p o s t e r i o r l y as f a r as t h e p o i n t where t h e M u l l e r i a n d u c t s pass i n t o the u r o g e n i t a l s i n u s .  The k i d n e y  c o n t i n u e s p o s t e r i o r l y f o r a s h o r t d i s t a n c e and ends i n a c o n i c a l p r o j e c t i o n o f t h e abdomen. The c e l l s o f the i n t e r r e n a l a r e columnar o r p o l y h e d r a l i n shape, w i t h g r a n u l a r a c i d o p h i l i c c y t o p l a s m .  The  c e l l s a r e s l i g h t l y l a r g e r than those o f t h e s u p r a r e n a l tissue.  The i n t e r r e n a l i s a d u c t l e s s g l a n d and i t has been  suggested by F r a s e r (1930), t h a t t h e s e c r e t i o n o f t h e c e l l s i s of a l i p o i d nature. A l t h o u g h t h e i n t e r r e n a l has no d i r e c t r e l a t i o n s h i p w i t h t h e autonomic nervous system, i t s h o u l d be b r i e f l y mentioned because o f i t s a s s o c i a t i o n w i t h t h e c h r o m a f f i n tissue.  I n higher v e r t e b r a t e s the adrenal glands a r e  composed o f two d i f f e r e n t elements,  a medullary or chromaffin  p o r t i o n , , and a c o r t i c a l o r I n t e r r e n a l p o r t i o n .  The two  types o f t i s s u e a r e s e p a r a t e d i n t h e r a t f i s h as they a r e i n nearly a l l f i s h .  .In the amphibia  and r e p t i l e s ,  there i s a  d e f i n i t e l y c l o s e r a s s o c i a t i o n o f the two t i s s u e s ; i n ' b i r d s the i n t e r r e n a l i s surrounded  by a network o f c h r o m a f f i n  t i s s u e ; i n mammals t h e c h r o m a f f i n t i s s u e becomes t h e m e d u l l a and i s surrounded  by t h e c o r t i c a l  t i s s u e ( C o l e 1941),  (Hyman 1942), ( K e n d a l l 1947). In f i s h the c h r o m a f f i n and i n t e r r e n a l t i s s u e s a r e d e r i v e d from s e p a r a t e embryonic a n a l g e n .  The c h r o m a f f i n  cells  - 33 and the sympathetic g a n g l i o n c e l l s have a common o r i g i n . They m i g r a t e from the c e n t r a l nervous system t h e n d i f f e r e n t i a t e a f t e r assuming anatomical p o s i t i o n s .  (ectoderm)  and  their respective  The i n t e r r e n a l i s d e r i v e d from t h e  mesoderm i n the m e d i a l d o r s a l p a r t o f the mesonephros (Arey 1934),  ( K e n d a l l 1947), (McEwan 1923).  Sympathetic System i n t h e T a l l . The k i d n e y c o n t i n u e s p o s t e r i o r l y i n t o a s m a l l c o n i c a l o u t p o c k e t i n g o f the abdominal c a v i t y .  The k i d n e y i s f u s e d  i n t o one c e n t r a l mass, l y i n g i m m e d i a t e l y below t h e d o r s a l aorta.  I n young specimens  o f a p p r o x i m a t e l y 10 cm.  p o s t e r i o r p r o j e c t i o n o f the abdomen i s 1 mm.  The  the sympathetic  nervous system t e r m i n a t e s a t the same p o i n t as the k i d n e y . The g a n g l i o n i s s i t u a t e d between the d o r s a l a o r t a and the remaining kidney t i s s u e ( F i g . 23).  Discussion The. p h y l o g e n e t i c s i g n i f i c a n c e o f Chimaeroids been the o b j e c t o f much c o n t r o v e r s y .  has  At one time t h i s  was thought to be the a n c e s t r a l form o f the  group  Elasmobranchs,  but the o p i n i o n a t p r e s e n t i s t h a t t h e y a r e a s p e c i a l i z e d group t h a t have branched o f f from the Elasmobranchs c a r r i e d on an independent e v o l u t i o n .  and have  Dean (1906), p r e s e n t s  the e m b r y o l o g i c a l e v i d e n c e o f Chimaeroid d e s c e n t .  There  can  be no doubt as t o t h e i r r e l a t i o n s h i p t o the s h a r k s , when the  - 34  -  p a l e o n t o l o g i c a l e v i d e n c e i s examined.  The e a r l i e s t  specimen  o f a c h i m a e r o i d n a t u r e appeared i n t h e J u r a s s i c e r a , whereas sharks were found i n f a r e a r l i e r ages.  The e m b r y o l o g i c a l  evidence p r e s e n t e d by Dean i s o n l y c o n c l u s i v e i f i t i s based upon the assumption t h a t i n ontogony  complex s t r u c t u r e s a r e  d e r i v e d f r o m l e s s complex s t r u c t u r e s . I n t h e i r independent descent from s e l a c h i a n s , t h e c h i m a e r o i d s have r e t a i n e d many p r i m i t i v e c h a r a c t e r i s t i c s ; a t the same t i m e s p e c i a l i z a t i o n o f s t r u c t u r e s has o c c u r r e d . In the s h a r k s s i m i l a r events took p l a c e , a l t h o u g h t h e s p e c i f i c c h a r a c t e r i s t i c s m o d i f i e d o r r e t a i n e d need n o t be o p p o s i t e i n t h e two groups. may  Thus one s t r u c t u r e o r one system i n a s p e c i e s  be more p r i m i t i v e t h a n i t i s i n a n o t h e r s p e c i e s ; y e t  the f o r m e r s p e c i e s i s n o t more p r i m i t i v e than t h e l a t t e r when judged as a whole.  Thus i n Hydrolagus the s e p a r a t e  g a n g l i a o f the vagus i n d i c a t e t h e p r i m i t i v e segmental n a t u r e o f the c r a n i a l and s p i n a l n e r v e s .  Other c h a r a c t e r i s t i c s  can  o n l y be i n f e r r e d as b e i n g p r i m i t i v e , such as t h e ramus from the vagus to the g a s t r i c g a n g l i o n . The p e c u l i a r i t i e s o f the nervous system and a l l i e d to i t , attention.  structures  o f c h i m a e r o i d s have a t t r a c t e d the most  W i l d e r (1877) w o r k i n g on the b r a i n o f  Chimaera  i s o f the o p i n i o n t h a t i t i s i n t e r m e d i a t e i n form between the b r a i n o f t h e c y c l o s t o m e s and t h a t o f the p l a g i o s t o m e s .  The  p o s t e r i o r r e g i o n s o f the b r a i n o f Chimaera appear t o have t h e i r homologues i n s h a r k s and s k a t e s ; but the r e m a i n i n g  - 35  -  d i v i s i o n s o f the b r a i n o f Chimaera do n o t appear homologous to t h e o r d i n a r y p l a g i o s t o m e b r a i n i A more a c c u r a t e comparison of homologies can be c a r r i e d out i f the embryonic development consideration.  i s taken i n t o  The nervous system o f the v e r t e b r a t e s d e v e l -  ops as a n i n v a g i n a t i o n o f the d o r s a l e c t o d e r m a l p l a t e . s e p a r a t i o n o f the n e u r a l tube from t h e o v e r - l y i n g  After  ectoderm,  a l a t e r a l p r o l i f e r a t i o n o f c e l l s from t h e n e u r a l tube o c c u r s . The r e s u l t i n g f o r m a t i o n i s the n e u r a l c r e s t , w h i c h on subsequent development becomes segmented.  These segments a r e  the rudiments o f t h e s p i n a l g a n g l i a ; t h e y e n l a r g e and grow downward between t h e n e u r a l tube and the s o m i t e s . n e u r a l c r e s t between t h e s o m i t e s d i s a p p e a r s . Kuntz  The (1911)  s t a t e s t h a t i n a l l v e r t e b r a t e s i n w h i c h the ontogeny o f the s y m p a t h e t i c nervous system has been t r a c e d , the l a t t e r  arises  from c e l l s w h i c h m i g r a t e p e r i p h e r a l l y from t h e c e r e b r o - s p i n a l nervous system.  As development advances, the c o n n e c t i o n  between the p r e s u m p t i v e g a n g l i a and the n e u r a l tube i s severed.  The n e u r a l c r e s t c e l l s become d i f f e r e n t i a t e d  g a n g l i o n c e l l s , n e u r o g l i a and s h e a t h c e l l s .  into  The g a n g l i o n  c e l l s send f i b r e s i n w a r d toward the n e u r a l tube t o form the d o r s a l a f f e r e n t r o o t , and the f i b r e growing outward the a f f e r e n t n e r v e .  forms  The v e n t r a l r o o t on t h e o t h e r hand, i s  an outgrowth f r o m t h e v e n t r o - l a t e r a l p o r t i o n of t h e s p i n a l cord.  A s h o r t d i s t a n c e beyond the g a n g l i o n the d o r s a l and  v e n t r a l r o o t s meet to form the s p i n a l n e r v e .  - 36 -  I n t h e p r i m i t i v e v e r t e b r a t e s such as Amphloxus, t h e d o r s a l and v e n t r a l r o o t s a r e s e p a r a t e d nerves.  The P e t r o m y z o n t i a  i n t o two d i s t i n c t  o f the Cyclostomata  arrangement o f t h e i r s p i n a l n e r v e s . a l s o o f the c l a s s C y c l o s t o m a t a ,  have a s i m i l a r  However i n the  Myxinoidea,  the d o r s a l and v e n t r a l r o o t s  o f a segment have f u s e d t o f o r m a s p i n a l nerve.'  I n the e a r l y  embryos o f S e l a c h i a n s t h e v e n t r a l and d o r s a l r o o t s a r e separated;  b u t the two r o o t s soon f u s e t o f o r m a mixed  s p i n a l nerve (Goodrich  1930).  I n Amphloxus the d o r s a l r o o t s o f t h e c r a n i a l and s p i n a l o u t f l o w c o n t a i n b o t h a f f e r e n t and e f f e r e n t f i b r e s . In the h i g h e r v e r t e b r a t e s , t h e d o r s a l r o o t s o f the c r a n i a l o u t f l o w c o n t a i n e f f e r e n t f i b r e s , whereas t h e d o r s a l r o o t s o f the s p i n a l n e r v e s c o n t a i n o n l y a f f e r e n t f i b r e s .  Thus  the sympathetic  o u t f l o w i s o n l y by v e n t r a l r o o t s , whereas the  parasympathetic  o u t f l o w i s p a r t l y t h r o u g h the d o r s a l r o o t s  of t h e V l l t h , I X t h , and X t h c r a n i a l n e r v e s , and p a r t l y through the v e n t r a l r o o t s o f t h e oculomotor and p e l v i c n e r v e s ( G o o d r i c h 1930).  The p r i m i t i v e v e r t e b r a t e c o n d i t i o n  i s s i m i l a r t o t h a t i n Amphloxus where a l l f i b r e s t o the v i s c e r a l e a v e the s p i n a l c o r d by the d o r s a l r o o t . has the sympathetic  How  then,  system come t o be connected w i t h t h e  c e n t r a l nervous system t h r o u g h the v e n t r a l r o o t s ?  Goodrich  i s o f the o p i n i o n t h a t p r e g a n g l i o n i c f i b r e s l e a v e by way o f the v e n t r a l r o o t i n segments i n w h i c h the d o r s a l and v e n t r a l r o o t s have J o i n e d , b u t t h a t i n segments where  they  - 37 -  do n o t j o i n , p r e g a n g l i o n i c f i b r e s r e m a i n i n the d o r s a l r o o t . Young (1933) f i n d s t h a t t h i s arrangement i s v e r y w e l l i l l u s t r a t e d i n Elasmobranchs.  Observations  on Hydrolagus  ( P i g . 25) agree w i t h those o f Young on Elasmobranchs. In t h e l o w e r v e r t e b r a t e s the v a g i a r e  comparatively  l a r g e , whereas the s y m p a t h e t i c system i s but p o o r l y d e v e l o p e d . The m a j o r i t y o f the i n t e r n a l f u n c t i o n s a r e governed by vagi.  the  Prom the o b s e r v a t i o n s o f Kuntz (1910b, 1911a, 1911b)  upon the v a r i o u s c l a s s e s o f v e r t e b r a t e s , a r e c i p r o c a l r e l a t i o n s h i p appears between the degree o f development o f the v a g i and  t h a t of the s y m p a t h e t i c t r u n k s .  Kuntz b e l i e v e s  t h a t the d e c r e a s e i n the r e l a t i v e s i z e o f the v a g i I n t h e h i g h e r v e r t e b r a t e s i s due  i n p a r t t o the f a c t t h a t t h e sense  organs assume the f u n c t i o n s of the l a t e r a l l i n e o r g a n s . I n the p r i m i t i v e c o n d i t i o n t h e r e c o u l d n o t have been such a g r e a t d i f f e r e n c e between t h e s y m p a t h e t i c and sympathetic.  P o s s i b l y t h e r e e x i s t e d o n l y one  the  para-  autonomic  system, and as the f u n c t i o n a l c o m p l e x i t i e s i n c r e a s e d  there  a r o s e a t the same t i m e a demand f o r i n c r e a s e d nervous c o n t r o l . Kunt,j (1910b) c o n c l u d e s t h a t the a n l a g e n o f the submucous, pulmonary and c a r d i a c p l e x u s e s vagus g a n g l i a by way  o f the v a g a l f i b r e s .  the s y m p a t h e t i c f i b r e s make c o n n e c t i o n s connection  myenteric,  o r i g i n a t e f r o m the At a l a t e r p e r i o d  w i t h them.  A further  between the two remains i n H y d r o l a g u s , where the  vagus sends a ramus t o t h e g a s t r i c g a n g l i o n , v i a the gastric ganglia.  pre-  - 38 L e y d i g (1851) w o r k i n g  on Chimaera monstrosa , d i d  n o t mention any c o n n e c t i o n between the g a s t r i c g a n g l i o n the vagus.  and  P r i o r to the i n v e s t i g a t i o n o f L e y d i g the a x i l l a r y  body o r "Nebenherzen", had been assumed t o be r e n a l h e a r t s s i t u a t e d on the s u b c l a v i a n a r t e r y .  I t was  L e y d i g who  pointed  out t h a t the s t r u c t u r e c o n t a i n e d g a n g l i o n i c c e l l s and the c e l l s s e n t f i b r e s i n t o the s u r r o u n d i n g  tissue.  observation revealed that the t i s s u e surrounding c l a v i a n a r t e r y and the g a n g l i o n i c c e l l s was tissue.  that  Later  the sub-  suprarenal  The g a n g l i o n i c c e l l s and the s u p r a r e n a l t i s s u e a r e  known as the a x i l l a r y body. I t i s n o t p o s s i b l e to s t a t e t h e p h y l o g e n e t i c  position  o f a s p e c i e s by o b s e r v a t i o n s upon a s i n g l e organ system o f t h a t s p e c i e s ; nor i s I t p o s s i b l e t o g i v e the taxonomic p o s i t i o n o f a l a r g e group by o b s e r v a t i o n s upon a s i n g l e species.  Thus i n the paast, a n i m a l s have been g i v e n  e t i c r a t i n g by o b s e r v a t i o n s upon the s k u l l ; n e g l e c t i n g the o t h e r organ systems. not c o n c l u s i v e .  phylogen-  entirely  Such i n v e s t i g a t i o n s a r e  I t i s n o t the i n t e n t i o n of t h i s paper t o  i n d i c a t e the p h y l o g e n e t i c importance o f Hydrolagus by o b s e r v a t i o n s upon i t s autonomic system a l o n e .  colliel I n the  c o u r s e o f t h i s i n v e s t i g a t i o n o t h e r f a c t o r s have been noted which might have a more d i r e c t b e a r i n g upon the p r i m i t i v e n e s s or s p e c i a l i z a t i o n of t h i s species.  The oesophagus  possesses  s t r i a t e d muscle and passes d i r e c t l y i n t o the s m a l l i n t e s t i n e , the m u s c u l a t u r e  o f w h i c h becomes g r a d u a l l y n o n - s t r i a t e d i n  - 39  the  t r a n s i t i o n from oesophagus t o s m a l l i n t e s t i n e .  The  l a t e r a l l i n e i n t h i s s p e c i e s ( F i g . 26) i s an open groove, but i n C a l l o r h y n c h u s I t i s a c l o s e d tube ( P a r k e r & H a s w e l l 1921).  The s t r a n g e d e n t i t i o n , w h i c h i s r o d e n t - l i k e i n  appearance, has g i v e n t h i s s p e c i e s the name o f " r a t f i s h " . These p e c u l i a r i t i e s among others, p r e s e n t problems o f taxonomic i m p o r t a n c e .  A thorough i n v e s t i g a t i o n o f t h e s e  p e c u l i a r i t i e s might throw some l i g h t upon t h e p h y l o g e n e t i c position of this  species.  The f a c t t h a t the autonomic nervous system o f Hydrolagus c o l l i e i i s s i m i l a r t o t h a t found i n Elasmobranchs is significant.  The e v i d e n c e o f t h i s i n v e s t i g a t i o n p o i n t s t o  the o r i g i n o f t h e Chimaeroids and Elasmobranchs from a common a n c e s t o r .  I f t h i s i s n o t t h e case t h e autonomic  nervous system would be m o d i f i e d i n a c c o r d a n c e w i t h t h e d i f f e r e n c e s i n the d i g e s t i v e t r a c t ; but the f a c t that the autonomic nervous systems a r e t h e same p o i n t s t o a common origin.  - 40  -  Summary  1. The  sympathetic ganglia  are arranged segmentally i n  abdominal c a v i t y , commencing a n t e r i o r l y a t the g a n g l i o n and  the  gastric  extending i n t o a c o n i c a l post-abdominal  pocket. 2. The  so c a l l e d "Nebenherzen" on the s u b c l a v i a n a r t e r y  are  not h e a r t s but a r e masses o f s u p r a r e n a l t i s s u e , w h i c h a r e homologous to t h e m e d u l l a o f the a d r e n a l g l a n d s o f mammals. 3. There i s no  structure  i s homologous to the 4. The  present i n the  digestive  stomach o f h i g h e r  t r a c t which  vertebrate's.  s p l a n c h n i c n e r v e s have t h e i r o r i g i n i n the  axillary  bodies. 5. A n t e r i o r  to the g a s t r i c g a n g l i a  "pregastric"  ganglia  i s a p a i r of  which receive  diffuse  a s h o r t b r a n c h from  the  v i s c e r a l vagus. 6. There i s no c a u d a l o u t f l o w f r o m the s p i n a l c o r d . 7. There are no  s y m p a t h e t i c f i b r e s to the h e a r t ; the  v a t i o n o f the h e a r t comes f r o m the c a r d i a c  p o r t i o n of  vagus, which sends a network o f f i b r e s to the and 8. The  innerthe  auricles  s i n u s venosus, but none t o the v e n t r i c l e . i n t e r - r e n a l does not r e c e i v e a n e r v o u s s u p p l y except  f o r the f i b r e s t h a t may vessels.  be c a r r i e d to i t by the  blood  The g a n g l i a formed by the r o o t s o f the vagus a r e from one a n o t h e r and n o t f u s e d .  separated  - 42 -  Acknowledgements I s h o u l d l i k e t o e x p r e s s my thanks t o Dr. W.A.  Clemens  f o r p e r m i s s i o n t o c a r r y out t h i s i n v e s t i g a t i o n i n t h e Department o f Z o o l o g y .  I am i n d e b t e d t o Dr. J.A.C. N i c o l f o r  na t e r i a l s and s u p p l i e s , f o r s u g g e s t i o n s on t e c h n i q u e and f o r the h e l p f u l c r i t i c i s m on t h e w r i t i n g o f t h i s t h e s i s .  The  a u t h o r a l s o w i s h e s t o thank the s t a f f o f t h e Zoology Department f o r t h e s u g g e s t i o n s and encouragement r e c e i v e d d u r i n g the c o u r s e o f t h i s work.  The major p a r t o f t h i s work c o u l d n o t  have been completed w i t h o u t t h e f i n a n c i a l h e l p r e c e i v e d from the N a t i o n a l R e s e a r c h C o u n c i l .  To Mr. R. W i l s o n , Mr. P. Howes  and crew o f t h e U r i e - M , t h e crew o f t h e Optua and the crew o f the  I n v e s t i g a t o r , I s h o u l d l i k e t o extend my s i n c e r e t h a n k s  for their help i n obtaining material f o r this  investigation.  L a s t l y I s h o u l d l i k e t o thank my p a r e n t s f o r t h e i r encouragement and f i n a n c i a l a s s i s t a n c e , w h i c h has e n a b l e d me to c o n t i n u e toward my M a s t e r ' s degree.  - 43 -  Literature Cited A d d i s o n , W.H.P., 1927, P i e r s o l ' s Normal H i s t o l o g y . J.B. 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Lea and F e b i g e r , P h i l a d e l p h i a .  - 44 -  K u n t z , A., 1945, Autonomic Nervous System. Lea and F e b i g e r , P h i l a d e l p h i a . - 1910a, The development o f t h e s y m p a t h e t i c nervous system i n mammals. J o u r . Comp. Neur. and P s y c h . 20:211-258. - 1910b, The r o l e o f t h e v a g i i n t h e development o f t h e s y m p a t h e t i c nervous system. A n a t . Anz. 381-390. - 1911a, The development o f t h e s y m p a t h e t i c nervous system i n c e r t a i n F i s h e s . J o u r . Comp. Neur. 21(2):177-215. - 1911b, The development o f t h e s y m p a t h e t i c n e r v o u s system i n A m p h i b i a . J o u r . Comp. Neur. 21(4):397-416. - 1911c, The e v o l u t i o n o f t h e s y m p a t h e t i c nervous system i n V e r t e b r a t e s . J o u r . Comp. Neur. 21(3);215-236. L e y d i g , F., 1851, Z u r Anatomie und H i s t o l o g i e d e r Chimaera m o n s t r o s a . A r c h , f u r Anatomie, P h y s i o l o g i e und WT s s e n s c h a f t l i c h e M e d i c i n - pp. 241-272. L i l l i e , R.D., 1948, H i s t o p a t h o l o g i c T e c h n i c . The B l a k i s t o n P r e s s , P h i l a d e l p h i a . L i s o n , L., 1936, H i s t o c h i m i e A n i m a l e . Gauthier-Villars, Paris. L i t t l e , M.E., 1932, S t r u c t u r e o f t h e V e r t e b r a t e s . Ray Long & R i c h a r d R. S m i t h , I n c . , New Y o r k . McEwen, R.S., 1923, V e r t e b r a t e Embryology. Henry H o l t and Company, New Y o r k . N e a l , H.V. and H.W. Rand, 1939, Chordate Anatomy. The B l a k i s t o n Company, P h i l a d e l p h i a . Pcvntin, G.F.A., 1946, M i c r o s c o p i c a l Technique f o r Z o o l o g i s t s . Cambridge U n i v e r s i t y P r e s s , Cambridge. P a r k e r , T . J . and W.A. H a s w e l l , 1921, A Textbook o f Z o o l o g y . M a c M i l l a n and Company, London. Ranson, S.W., 1947, The Anatomy o f t h e Nervous System. W.B. Saunders and Company, P h i l a d e l p h i a . W i l d e r , B.G., 1877, On t h e b r a i n o f Chimaera monstrosa. P r o c . Acad. Nat;. Sc. P h i l . pp. 219-250.  - 45 -  Young, J.Z., 1933, The autonomic nervous system o f S e l a c h i a n s , Quart. J o u r . M i c . Sc. 75:571-624.  Plate  F i g u r e 1.  I  i  Specimen o f Hydrolagus c o l l i e i , x 1/4  ( a f t e r Dean)  Classification: Phylum  Chordata  (Vertebrata)  Subphylum  Craniata  Class  Elasmobranchii  Subclass  Holocephali  Order Family  Chimaeridae  Genus  Hydrolagus  Species  colliei  Description: The body i s e l o n g a t e , w i t h a s t o u t i s h a n t e r i o r end and t a p e r i n g p o s t e r i o r l y i n t o a w h i p - l i k e  tail.  The mouth i s s i t u a t e d v e n t r a l l y , w i t h I n c i s o r - l i k e teeth. scales.  The s k i n i s t h i n and smooth w i t h o u t any The males have a c l u b - s h a p e d s p i n y  process  on the head above the snout, w h i c h f i t s i n t o a shallow depression; pelvic claspers.  they a l s o have two p a i r s o f  The c o l o r i s s i l v e r y w i t h p a t c h e s  of g o l d e n p a l e brown and o t h e r hues. Wilby,  1946).  (Clemens and  -o > H m FIG.  Plate F i g u r e 2.  Diagrammatic autonomic  representation  nervous  o f t h e mammalian  system.  Sympathetic - - - -  II  preganglionic  Sympathetic p o s t g a n g l i o n i c  fibres. fibres.  Parasympathetic  preganglionic  Parasympathetic  postganglionic  fibres. fibres.  Plate F i g u r e 3.  Diagrammatic visceral  III  r e p r e s e n t a t i o n o f t h e mammalian  reflex arc.  ( A f t e r B e s t and  Taylor)  PLATE  nr  DORS ROO  GLION  FIG. 3  DIAGRAM  OF VISCERAL  REFLEX ARC  DORSAL HORN  DORSAL ROOT  VENTRAL HORN SPINAL  VISCERAL  AFFERENT  CORD  FIBERS  WHITE  RAMUS  COMMUNICANS GREY RAMUS COMMUNICANS  COLLATEH SPINAL  GANGLION  NERVE  TO VISCERA SYMPATHETIC TRUNK  Plate F i g u r e 4.  Secretory  IV  f i b r e s of the v a g u s .  (Bodian's P r o t a r g o l , x  F i g u r e 5.  100)  1.  gland  2.  f i b r e s from b r a n c h i a l vagus  3.  b r a n c h i a l vagus  4.  efferent branchial  5.  cartilage  6.  muscle.  Vagal g a n g l i a  artery  (Bodian's P r o t a r g o l , x  1.  d o r s a l r o o t o f vagus  2.  2nd  vagal  ganglion  3.  3rd vagal  ganglion  4.  ganglion  5.  cartilage  6.  muscle.  440)  o f l a t e r a l l i n e b r a n c h of vagus  Plate F i g u r e 6.  V a g a l g a n g l i a No. 2 and No. 4 (Bodian's P r o t a r g o l x  F i g u r e 7.  V  440)  1.  g a n g l i o n o f l a t e r a l l i n e b r a n c h of t h e vagus  2.  g a n g l i o n o f v i s c e r a l b r a n c h o f vagus  V a g a l g a n g l i a and d o r s a l r o o t g a n g l i a (Bodian's P r o t a r g o l , x  440)  1.  g a n g l i o n o f l a t e r a l l i n e b r a n c h o f t h e vagus  2.  d o r s a l r o o t g a n g l i o n o f s p i n a l nerve  3.  s p i n a l nerve  4.  muscle  5.  visceral  vagus.  PLATE  FIG. 7  "SF  P l a t e VI  F i g u r e 8.  V i s c e r a l vagus n e r v e (Bodian's P r o t a r g o l , x 440) 1.  v i s c e r a l vagus n e r v e  2.  s p i n a l nerve  3.  l a t e r a l l i n e nerve.  Plate  F i g u r e 9.  VII  ( M a l l o r y ' s T r i p l e , x 440) 1.  mucous membrane o f oesophagus  2.  m u s c u l a r i s mucosa  3.  branches o f v i s c e r a l vagus  • 4.  f i b r e s t o m u s c u l a r i s mucosa.  PLATE  FIG. 9  2H  Plate  F i g u r e 10.  VIII  A x i l l a r y body, (Bodian's P r o t a r g o l , x 440) 1.  subclavian  artery  2.  s p i n a l nerve  3.  communicating r a m i from s p i n a l n e r v e t o a x i l l a r y body  4.  a x i l l a r y body.  PLATE  TOE  P l a t e IX  Figure  11.  Vasomotor f i b r e s ,  (Bodian's P r o t a r g o l , x  1.  subclavian  2.  s p i n a l nerve  3.  branch to subclavian  440)  artery  a r t e r y from s p i n a l n e r v e .  PLATE  HI  Plate X  F i g u r e 12.  P o s i t i o n o f A x i l l a r y B o d i e s , (Bodian's P r o t a r g o l , x 40) 1.  dorsal  2.  subclavian  3.  a x i l l a r y body  4.  s p i n a l nerve  5.  posterior cardinal  6.  notochord  7.  oesophagus  8.  liver.  F i g u r e 13.  aorta artery  sinus  Formation of splanchnic x 100) 1.  dorsal  aorta  2.  coeliac artery  3.  splanchnic  4.  liver  5.  intestine.  nerve  n e r v e , (Bodian's  Protargol,  PLATE  FIG.  13  X  Plate  F i g u r e 14.  XI  L o n g i t u d i n a l nerves i n the i n t e s t i n e , (Mallory's T r i p l e , x 1.  F i g u r e 15.  40)  nerve trunk.  F i r s t p a i r of sympathetic g a n g l i a p o s t e r i o r to gastric ganglia, 1.  sympathetic  2.  dorsal aorta  3.  liver  4.  notochord.  (Bodian's P r o t a r g o l , x  ganglion  100)  PLATE  F I G . 15  2 1  Plate  Figure  16.  Anterior x  Figure  sympathetic  ganglia,  (Bodian's  Protargol,  100)  1.  sympathetic  2.  posterior cardinal  3.  liver  4.  notochord  5.  muscle  6.  dorsal  17.  XII  First  ganglion sinus  aorta.  p a i r sympathetic  (Bodian's  Protargol, x  1.  dorsal  aorta  2.  sympathetic  3.  kidney  ganglion  tubules.  ganglia 100)  i n kidney  region,  PLATE  FIG.  17  XH  Plate  F i g u r e 18.  XIII  Sympathetic c e l l s o f an a n t e r i o r g a n g l i o n , (Hematoxylin 1.  ganglion  2.  muscle.  and e o s i n , x cell  440)  PLATE  RG.  18  SU-  P l a t e . XIV  F i g u r e 19.  A x i l l a r y ganglion,  (Hematoxylin  1.  subclavian artery  2,  suprarenal t i s s u e .  F i g u r e 20.  Gastric ganglion  cells,  (Hematoxylin  eosin, x  and  1.  sympathetic  ganglion  2.  suprarenal t i s s u e .  440)  cell  and e o s i n , x  440)  PLATE  -2HL  Plate  F i g u r e 21.  XV  G a s t r i c g a n g l i o n c e l l s and s u p r a r e n a l c e l l s o f a x i l l a r y body, ( H e m a t o x y l i n and e o s i n , x 950) 1.  F i g u r e 22.  sympathetic  cell.  I n t e r r e n a l t i s s u e , (Holmes* s i l v e r , x 100) 1.  interrenal tissue  2.  kidney.  Plate  F i g u r e 23.  XVI  Sympathetic i n t a i l r e g i o n , (Holmes' s i l v e r , x  440)  1.  s y m p a t h e t i c g a n g l i o n and  2.  terminal p o r t i o n of  3.  dorsal aorta.  F i g u r e 24.  suprarenal  kidney  Sympathetic g a n g l i o n a s s o c i a t e d w i t h (Holmes' s i l v e r , x 1.  sympathetic  2.  kidney.  440)  ganglion  tissue  kidney,  PLATE "SSL  FIG.  24  Plate  F i g u r e 25.  XVII  D o r s a l motor b r a n c h o f the vagus. (Holmes' s i l v e r and l i g h t g r e e n , x 1.  ganglion  2.  dorsal root  3.  v e n t r a l root  4.  cartilage  5.  medulla.  440)  PLATE  I  3  F T G .  2 5  »  Plate  F i g u r e 26.  Lateral l i n e canal,  XVIII  (Bodian's P r o t a r g o l , x  100)  PLATE  FIG. 26  XVTH  

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