220 



OUR BODIES AND HOW WE LIVE 



v-ist and 2nd 

 'l Spinal Nerves 



FIG. 138. BLACKBOARD SKETCH. 



Diagram of the Distribution of 

 the Cranial Nerves. 



The cranial nerves are thus arranged in pairs : 



1, olfactory nerves, special nerves of smell; 



2, optic nerves, passing to each eyeball, de- 

 voted to sight ; 3, 4, and 6 control the muscles 

 of the eyes; 5, trifacial in three branches, 

 which proceed mainly to the face, partly sen- 

 sory and partly motor ; 7, facial nerves, con- 

 trolling the facial muscles ; 8, auditory, or 

 nerves of hearing, distributed to the organs 

 of hearing ; 9, glossopharyngeal nerves, partly 

 sensory and partly motor: each nerve con- 

 tains two roots, one a nerve of taste, the other 

 a motor nerve, which controls the muscles 

 engaged in swallowing; 10, pneumogastric 

 nerves (described in Sec. 297); n, spinal 

 accessory nerves, supplying some of the mus- 

 cles of the neck and back; 12, hypoglossal 

 nerves, controlling the movements of the 

 tongue in speech and swallowing. 



hemisphere andobserve the 

 gray and the white matter 

 inside. The brain should 

 be first examined as a 

 whole, and compared with 

 the description given in the 

 text, or with the diagrams 

 of the human brain. With 

 careful dissection and by 

 comparison with diagrams, 

 most of the twelve pairs 

 of cranial nerves can be 

 identified. 



NOTE. A fresh brain 

 is too soft for handling or 

 for careful study. Hence 

 it should be hardened and 

 made ready for use several 

 weeks before it is needed. 

 A mixture of one fourth of 

 an ounce of bichromate 

 of potash and one ounce 

 of a forty-per-cent solu- 

 tion of formalin to about 

 one quart of water makes 

 a useful hardening and 

 preserving fluid. 



297. The Cranial 

 Nerves. From each 

 side of the brain pro- 

 ceed twelve pairs of 

 nerves, called cranial 

 nerves. They pass out 

 of the skull in pairs 

 through little holes in 

 its base, and supply the 



