CRANIAL NERVES 207 



VI. The abducens supplies the external rectus muscle of the 

 eye. 



VII. The facial is a motor nerve which parallels in its dis- 

 tribution the sensory portion of the fifth. It supplies the 

 superficial muscles which give the features the power of reflect- 

 ing the emotions. If the nerve is sectioned, the face on that 

 side is devoid of motion and becomes smooth and expressionless. 

 The eyelids do not close and the lips do not oppose properly 

 on account of the defective action of the orbicularis muscle. 

 There is difficulty in drinking and in speaking for the same 

 reason. 



VIII. The cochlear portion of the auditory is the nerve of 

 hearing. The cell bodies of these fibers are situated in the spiral 

 ganglion of the cochlea, which is homologous with the dorsal 

 root ganglia of spinal nerves. One axon reaches the organ of 

 Corti, and the other passes to the bulb, where it terminates in 

 the dorsal or ventral nucleus of the eighth nerve. The fibers 

 entering the ventral nucleus may be continued to the superior 

 quadrigemina, passing by way of the trapezium, the superior 

 olive, the lateral lemniscus, and the inferior collicus. They may 

 give collaterals to each, or may end in any of these gray masses. 

 Cells of the dorsal nucleus send their axons across the floor 

 of the fourth ventricle, forming the strise acusticse. 



The vestibular portion of the eighth nerve transmits impulses 

 from the ampullae of the semicircular canals, and therefore 

 serves the sense of equilibrium. The cell bodies of these fibers 

 are located in the vestibular ganglion, and their central axons 

 are divided into a branch passing cephalad and one passing 

 caudad, which terminate with various nuclei, and also pass 

 to the cerebellum. 



IX. The glossopharyngeal nerve is the nerve of taste and of 

 deglutition. It is motor as well as sensory in function. Its 

 distribution is to all the muscles of deglutition, and stimulation 

 contracts, while section paralyzes them. The very numerous 

 connections of the nerve complicate its origin and interfere with 

 a clear comprehension of the unaided function of the nerve. 

 The cells of the fibers lie in the bulb on the medial side of the 

 tractus solitarius. Their axons are sent cephalad through the 

 medial lemniscus. Latest investigations have shown that the 

 chief path of the taste sense is over the chorda tympani nerve, 



