NERVES OF MAMMALIA. 181 



nerve is proportionally larger in a Baboon : and he also notices 

 the large size of this nerve in the Jaguar. The nerves of the 

 palm are proportionally smaller in Apes than in Man, and do 

 not terminate in such thick brushes of filaments at the tips of the 

 fingers; but the branches from the musculo-spiral and ulnar 

 nerves to the back of the hand are larger in proportion than in 

 Man. 1 Many Quadrumana have the ganglion on the termination 

 of the spiral nerve at the back of the wrist ; but in the Felidce 

 there is only a slight enlargement at that part of the nerve. 



§ 212. Sympathetic system. — This, as an addition to the general 

 nervous system, is a speciality of the Vertebrate subkingdom : as 

 such it dawns in Myxinoids, at the confluence and intestinal 

 production of the two vagal trunks, and is differentiated by pro- 

 gressive steps, till it attains the general condition defined in 

 vol. i. p. 318, § 57. 2 



Where it begins in the series there the chief centres are after- 

 wards established, as the semilunar ganglions and solar plexus, so 

 called from the multitudinous rays that diverge therefrom ; they 

 are early and distinctly visible in the mammalian embryo. The 

 ganglions of the sympathetic vary in the proportion of the grey 

 or cellular and filamentary or tubular constituents. The cellular 

 part forms a greater proportion of the semilunar ganglions in 

 Man than in most lower Mammals : and it is greater in Car- 

 nivora than in hoofed quadrupeds. The filaments radiating 

 from the semilunar ganglions collect themselves into interlaced 

 groups named after the viscera they mainly supply, as, the 

 ' gastric,' ' hepatic,' c splenic,' i mesenteric,' ' renal,' i spermatic,' 

 &c. : the chief branches of all these plexuses attach themselves 

 to the arteries of the several organs : in the large gastric plexus 

 of the Ruminants they accompany these to the several divisions 

 of the complex stomach. In the Carnivora branches of the 

 superior mesenteric pass in a more definite form to the aggregate 

 of mesenteric glands at the root of the mesentery. In Perisso- 

 dactyles, in which the caecum and colon are remarkable for size 

 and complexity, the superior mesenteric plexus, supplying these 

 parts of the large as well as the small intestines, is proportionally 

 larger than in other Mammals, especially as compared with the 

 inferior mesenteric plexus in Carnivora and Quadrumana. In 



1 liv. p. 1 93. Much of the foregoing description is abridged from this rich store- 

 house of Comparative Neurology. 



3 This true idea of the series of ganglions and nerves, called * sympathetic' in Man, 

 once clearly attained, will leave little room for speculations as to whether the ner- 

 vous system of insects answers to the myelencephalic or sympathetic part, exclusively, 

 of that of Vertebrates. 



