176 



Basic Structure of Vertebrates 



These ganglions are segmental in arrangement, each pair corresponding 

 to an adjacent myomere and its pair of spinal nerves. In the cervical 

 region of each autonomic cord there are usually three ganglions, the 

 anterior and middle cervical and, behind them, a large stellate 

 ganglion which is apparently produced by fusion of several posterior 

 cervical and anterior thoracic ganglions (Figs. 156, 157). Each cord and 

 its several ganglions are often described as being a "chain" of gan- 

 glions. Accordingly, the ganglions are commonly called "chain gan- 

 glions," otherwise lateral ganglions. 



Fig. 155. Autonomic sys- 

 tem of right side of a frog. 

 Somatic nerves are dotted, 

 autonomic black, (a) Atlas; 

 (ai) common intestinal ar- 

 tery; (ao) aorta; (c) coccyx; 

 (cr) crural nerve; (i) sciatic 

 nerve; (ih) iliohypogastric 

 nerve; (./') jugal ganglion; (r) 

 radices aortae; (s) base of 

 skull; (sp) splanchnic nerve; 

 (si) autonomic trunk; (II- 

 XI) second to eleventh 

 trunk nerves. (After Gaupp. 

 Courtesy, Kingsley: "Com- 

 parative Anatomy of Verte- 

 brates," Philadelphia, The 

 Blakiston Company.) 



The double series of ganglions is continued forward into the head 

 by pairs, usually five, of ganglions which are external to the cranium and 

 in close ventrolateral proximity to it. These, mentioned in order from 

 anterior backward (Fig. 157), are the ciliary (A, lying in the orbit), 

 sphenopalatine (B, in the roof of the mouth), sublingual and sub- 

 maxillary (E, each close to the salivary gland of the same name), and 

 the otic (C, at the base of the external ear). (See also Fig. 159.) From 

 the anterior cervical ganglion, a small nerve extends forward and con- 

 nects, directly or indirectly, with the several cephalic ganglions of the 

 corresponding side of the head. 



All of these paired autonomic ganglions are connected with the 

 cerebrospinal system. Each lateral ganglion within the thoracic, lum- 

 bar, and sacral regions, with the occasional exception of one or two 



