CRANIAL NERVES. 203 



Properties and Functions of the Branches Given off in the Aqueduct 

 of Fallopius. 



1. The large petrosal, when stimulated, gives rise to a dilatation of the blood- 

 vessels and a secretion from the mucous membrane of nose, soft palate, 

 upper part of the pharynx, roof of the mouth, and gums. It therefore 

 contains vaso-motor and secretor fibers, which are in relation with the 

 spheno-palatine ganglion. 



2. The tympanic branch causes the stapedius muscle to contract. 



3. The chorda tympani influences the circulation of the blood around, and the 

 secretion of saliva from, the submaxillary glands, and through the nerve of 

 Wrisberg endows the anterior two-thirds of the tongue with the sense of taste. 

 Galvanization of the chorda tympani dilates the blood-vessels, increases the 

 quantity and rapidity of the stream of blood, and increases the secretion of 

 sali va. Division of the nerve is followed by contraction of the vessels, and 

 arrest of the secretion, and a loss of the sense of taste on the same 

 side. It therefore contains vaso-motor, secretor and gustatory nerve- 

 fibers. 



Function. The facial is the nerve of expression, and coordinates the 

 muscles employed to delineate the various emotions, influences the sense of 

 taste and the secretions of the submaxillary and sublingual glands. 



Eighth Nerve. Acoustic Nerve. 



The eighth nerve consists of two portions, a cochlear or auditory and a 

 vestibular or equilibratory. 



Origin. The cochlear portion has its origin in the bipolar nerve-cells of 

 the spinal ganglion located in the spiral canal near the base of the osseous 

 lamina spiralis. The vestibular portion has its origin in the bipolar nerve- 

 cells of the ganglion of Scarpa located in the internal auditory meatus. 



Distribution. The common trunk of the eighth nerve, consisting of both 

 the cochlear and vestibular portions, emerge from the internal auditory 

 meatus after which it passes backward and inward as far as the lateral aspect 

 of the pons, where the two main divisions again separate. The cochlear 

 portion passes to the outer side of the restiform body; the vestibular portion 

 passes to the inner side of the restiform body to the dorsal portion of the pons. 

 After entering the pons the fibers composing both portions come into histo 

 logic relations with different groups of nerve-cells. 



Properties. Stimulation of the cochlear nerve is unattended by eithei 

 motor or sensor phenomena. Division of the nerve is followed by a loss of 

 hearing. Destruction of the semicircular canal, involving a lesion of the 



