XVI 



THE NERVOUS SYSTEM 



295 



separated from the latter by a shallow lateral sulcus. Unlike 

 the cerebral hemispheres, they are closely fused together in 

 the middle line ; on the ventral side, however, they show 

 a well-marked median fissure. Anteriorly they give off the 

 olfactory nerves. 



The Cranial Nerves. — There are ten pairs of nerves in 



Fig. 85. — Diagram of the distribution of the fifth, seventh, ninth, and tenth 

 cranial nerves, the first spinal nerve, and the anterior part of the sympa- 

 thetic, .'if, systemic arch of aorta ; ^r.//, brachial plexus ; Z?.^(?, dor- 

 sal aorta ; du, duodenum ; H, heart ; Hy, hyoid with hy^ anterior and hy'^ 

 posterior horns ; L, lung ; A^, nasal bone ; On, orbit ; Pul, pulmonary 

 artery; Sp.A, splanchnic, or coeliaco-mesenteric artery; St, stomach; 

 Sy, sympathetic ; //, cut end of optic nerve ; V^, ophthalmic, V^, maxil- 

 lary, and V^, mandibular branch of fifth, or trigeminus nerve; F/P, 

 palatine, and VI l'^, hyomandibular branch of facial ; IX, glossopharyn- 

 geal nerve ; X, vagus with Xcd, cardiac, Xgas, gastric, Xlar, laryngeal, 

 and Xpul, pulmonary branches; / Sp, first spinal nerve, or hypoglossal; 

 2 sp-^ sp, second to fifth spinal nerves. (From Parker and Parker's 

 Zoology, slight'y modified from Howes.) 



