512 GENERAL ANATOMY. 



cervical ganglions and the cardiac nerves. In old age the gan- 

 glions are paler and drier than in the adult age. 



The ganglions and cords of the sympathetic nerves are found 

 in foetuses deprived of brain, and in those which are deprived 

 of brain and spinal marrow. 



810. The vertebrate* animals alone have a particular nerv- 

 ous system for the organs of vegetative functions. 



In fishes the sympathetic nerve consists of a very fine 

 thread, with few or no ganglions. 



In reptiles it is more distinct: it unites together the inter- 

 vertebral nerves, and penetrates into the cranium united with 

 the par vagum. 



In birds it penetrates into the cranium with the par vagum 

 and the glosso-pharyngeal ; it communicates with the fifth and 

 sixth pairs; it presents in the neck an apparent interruption, 

 arising from its being contained in the .vertebral canal: it is 

 very distinct and.ganglionary in the thorax, and is prolonged 

 even unto- the caudal vertebrae. 



in the mammalia the sympathetic nerve does not differ much 

 from that of man. 



Meckel and Weber have remarked that the sympathetic 

 nerve is so much the smaller, relative to the body, as the -ani- 

 mal is farther removed from man. A second general observa- 

 tion is that the sympathetic nerve and the par vagum are in an 

 inverse relation with respect to their development; so that 

 they mutually supply the place of each other, in the vegeta- 

 tive life to which they both belong. It is nepessary also to 

 remark, that the sympathetic nerve is developed in all animals 

 in proportion to their circulatory apparatus, to which it in 

 great part belongs. 



812. The ganglionary nervous system, which exists in all 

 animals, which, in the vertebrata, forms a system apart, in 

 connexion with the nervous centre whose development it pre- 

 cedes^ which preserves on one part the stale of dissemination 

 that the nervous system of the invertebrata presents, and 

 which forms also some principal centres, as the cardiac plexus, 



* Weber, Jinatomia compar. nervi sympath.; Lips., 1817. 



