874 



BIOLOGY. 



[Book vi. 



Like the arthropods and the moUusks the vertebrates have^a 

 special nervous network for the apparatus of the vegetative life. 

 This network has been called in its ensemble sympathetic 

 nervous system, and we are obliged, to render what follows 

 intelligible, to give a succinct description thereof. 



Here still there is no essential difference between the superior 

 invertebrates and the vertebrates. The dissemblances bear on 



Fia. 65. 



Brain of rabbit ; A, upper aspect ; B, netlier aspect ; Zo, olfactory lobe ; I, anterior brain ; 

 III^ median brain ; IV, posterior brain (cerebellum) ; V, elongated marrow ; A, hypophy- 

 sis ; 2, optical nerve ; 3, oculo-motor nerve ; 5, trigeminus nerve ; 6, abductor nerve ; 

 7, 8, facial and acoustic nerves. In A has been removed the roof of the right hemisphere ■ 

 to show the interior of the lateral ventricle, the striated bodies which are found therein 

 before and behind the four-piUared fornix with the commencement of the Hippocampus 

 Ttiasor. 



the exterior arrangement, on the morphology. In sum, in the 

 invertebrates and in the vertebrates there is a special nervous 

 network destined for the organs, systems, and apparatus of the 

 vegetative life : namely, for the digestive tube, for the respira- 

 tory organs, for the circulatory system, for the genito-urinary 

 organs. In both the invertebrates and vertebrates this system 

 lias its origin, or at least its roots, in the great nervous centres. 

 Following the distribution of the sympathetic branches to their 

 furthest extremities, we see that their fibres are distributed 

 wherever there are vegetative contractile elements, smooth 



