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 



F(G. 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. Ao, systemic arch of aorta ; ir.p/, brachial plexus ; D.Ao, dor- 

 sal aorta ; rf«, duodenum; A', heart ; //)', hyoid with /yi anterior and /y- 

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

 artery; i>^.^, splanchnic, or cceliaco-mescnteric artery; St, stomach; 

 6j, sympathetic ; //, cut end of optic nerve ; Fi, ophthalmic, K^, maxil- 

 lary, and V^, mandibular branch of fifth, or trigeminus nerve; VW^, 

 palatine, and VI ft, hyoinandibular branch of facial ; IX, glossopharyn- 

 geal nerve; A', vagus with A'a^, cardiac, A'^rt.r, gastric, A'/iz^, laryngeal, 

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

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

 Zoology, slightly modified from Howes.) 



