THE FIFTH CRANIAL NERVE. 525 



iii. Vasomotor or vase-inhibitory influences are chiefly con- 

 nected with the secretory function, since dilatation of the vessels 

 of the glands accompanies the increased secretion that follows 

 stimulation of the nerves going to the glands. 



iv. The following afferent impulses are said to travel along the 

 track of the portio dura and its branches: (1) Special taste sen- 

 sations, which are chiefly located in the chorda tympani branch, 

 may be explained by the branches of communication which pass 

 from the trunk and petrous ganglion of the glosso-pharyngeal to 

 the portio dura at its exit from the foramen, or by the connec- 

 tion in the drum of the ear between the tympanic branch of the 

 glosso-pharyngeal and the geniculate ganglion of the portio dura 

 through the lesser superficial petrosal nerve. (2) Ordinary 

 sensations, which are also located in the chorda tympani, are 

 said to traverse this nerve in an afferent direction until it comes 

 near the otic ganglion, when the sensory fibres leave the chorda 

 and pass to the inferior division of the fifth nerve through the 

 otic ganglion. 



Injury of the facial nerve in any of the deeper parts of its 

 course gives rise to the striking group of symptoms known as 

 facial paralysis, the details of which are too long to be given 

 here. When it is remembered that muscles aiding in expression, 

 mastication, deglutition, hearing, smelling and speaking are para- 

 lyzed, and that taste, salivary secretion and, possibly, ordinary 

 sensation are impaired, one can form some idea of the complex 

 pathological picture such a case presents. 



V. N. TRIGEMINUS, OR TRIFACIAL NERVE. 

 This nerve transmits both efferent and afferent impulses, which, 

 however, are carried by two different strands of fibres. The motor 

 part, which arises from a gray nucleus in the floor of the fourth 

 ventricle, is much the smaller of the two, and has been compared 

 to the anterior root of a spinal nerve. The large sensory division 

 springs from a very extensive tract, whi,ch can be traced from the 

 pons Varolii through the medulla to the lower limit of the olivary 

 body, and on to the posterior cornua of the spinal marrow. This 

 set of fibres has been likened to the posterior root of a spinal 



