THE CRANIAL NERVES. 547 



membrane of the nose, soft palate, upper part of the pharynx, roof 

 of mouth, gums, and upper lip. 



The small petrosal nerve is' also composed of efferent fibers; 

 shortly after leaving the facial it is joined by a small nerve, derived 

 from Jacobson's branch of the glosso-pharyngeal, which is also effer- 

 ent in function ; for stimulation of Jacobson's nerve as well as stimu- 

 lation of the otic ganglion is followed by the same result: viz., dilata- 

 tion of the blood-vessels of, and secretion from, the mucous membrane 

 of the cheek, lower lip, and gums, and of the parotid and the orbit 

 glands. 



The stapedius nerve, distributed directly to the stapedius muscle, 

 is motor in function. 



The Chorda Tympani. Stimulation of the chorda tympani nerve 

 in the tympanic cavity produces dilatation of the blood-vessels of, 

 and an increased production and discharge of saliva from, the sub- 

 maxillary and sublingual glands. 



Division of this nerve is followed by a contraction of the blood- 

 vessels and a diminution of the secretion. From these results it is 

 certain that the chorda tympani contains both vaso-dilatator and secre- 

 tor fibers. Nicotin applied to the submaxillary and sublingual gang- 

 lia abolishes the effects of stimulation of the chorda tympani. It 

 does not prevent the same effects when the ganglia themselves are 

 stimulated. It is clear, therefore, that the vaso-dilatator and secretor 

 fibers arborize around the cells of the ganglia and are not distributed 

 directly to the gland structures. It is highly probable that the efferent 

 fibers in the chorda tympani emerge from the pons by way of the 

 pars intermedia. 



Division of the chorda in the tympanum is also followed by a loss 

 of taste in the anterior two-thirds of the tongue. For this and other 

 reasons the chorda tympani has long been regarded as the nerve of 

 taste for this region. The specific physiologic stimulus to the chorda 

 tympani nerve is organic matter in solution acting on the peripheral 

 terminations of the nerve in the mucous membrane of the tongue. 

 The exact pathway for these afferent or gustatory fibers beyond the 

 geniculate ganglion has long been a subject of much discussion. 

 According to some observers these fibers enter the great petrosal 

 nerve, pass forward as far as the spheno-palatine ganglion, then into 

 the superior maxillary division of the trigeminal, and so to the brain. 

 According to others, these fibers pass into the pars intermedia, into 

 the pons, where they terminate around the sensor end- nucleus of 

 the glosso-pharyngeal. The evidence for and against either of these 

 two views is most conflicting and insufficient to justify positive state- 

 ments one way or the other. To the writer the weight of evidence 

 seems to favor the view that the gustatory fibers have their origin in 

 the geniculate ganglion; that they pass centrally through the pars in- 



