374 



A TEXTBOOK OF PHYSIOL< H ; V 



impressions, such as are aroused by thinking of a favourite meal. 

 This may make the mouth water, especially in a state of hunger. 



The efferent nerves from the centre are the auriculo-temporal 

 nerve to the parotid gland, the chorda tympani nerve to the sub- 

 maxillary and the sublingual glands. The sympathetic system also 

 gives a weak effector nerve to the submaxillary gland and sublingual 

 gland. 



The course qf the effector nerves is somewhat complicated. While 

 stimulation of the fifth nerve above the otic ganglion is without effect 

 upon the secretion of the parotid gland, stimulation of the ninth nerve 

 as it leaves the brain causes a flow of saliva. The effector fibres 

 therefore pass from the ninth nerve to the fifth. They follow the 

 path of Jacobson's nerve, and the small superficial petrosal, to the 

 otic ganglion, which is the cell-station of this nerve. 



(Buccal 

 \ mucous > 

 (membrane. 



Tongue 



-<Memory. 



Parotid gland 

 (byauriculo - temporal 

 nerve) 



Submaxillary gland 

 (by chorda tympani) 



Sublingual gland 

 (bu chorda tumpant 

 J nerve) 



\ By vagus to stomac'i 

 \ for gastric juice. 



FIG. 192. DIAGRAM TO SHOW CONNECTIONS OF THE NERVOUS CENTRE CONCERNED 

 IN THE SECRETION OF SALIVA AND GASTRIC JUICE. 



The stimulation of the sympathetic nerve to the parotid does not 

 effect a flow of saliva. It is stated, however, that if the nerve be 

 stimulated at the same time as Jacobson's nerve, or the glosso-pharyn- 

 geal, the solid content of the saliva, particularly the organic, is con- 

 siderably raised. 



In regard to the submaxillary and sublingual glands, it has been 

 proved experimentally that if the lingual nerver be cut high up, reflex 

 secretion of saliva still occurs. Similarly, stimulation of the peripheral 

 end of this nerve, and after it has been cut high up, has no effect 

 upon secretion. On the other hand, if the chorda tympani nerve 

 be cut, reflex secretion is abolished ; while stimulation of the peripheral 

 end causes a copious flow of watery saliva. This nerve issues from 

 the seventh nerve as a small branch, and, joining the lingual in the 

 lower part of its course, runs with it for a short way, and then passes 

 to the glands. The course of the fibres, however, is interrupted by 

 the interposition of ganglia. The fibres to the sublingual gland end 

 in a small ganglion, known as the " submaxillary ganglion " (it ought 

 to be termed "sublingual"); the fibres to the submaxillary gland 

 end in a minute ganglion situated in the hilus of the gland. The cell 



