396 NERVES OF THE SUBMAXILLARY GLAND. [BOOK n. 



225. The submaxillary gland is supplied with two sets of 

 nerves. These are represented in Fig. 62, which is a very diagram- 

 matic rendering of the appearances presented when the submaxillary 

 gland is prepared for an experiment in a dog, the animal being 

 placed on its back and the gland exposed from the neck. The one 

 set, and that the more important, belongs to the chorda tympani 

 nerve (ch.t"). This is a small nerve, which branches off from the 

 facial or seventh cranial nerve in the Fallopian canal before the 

 nerve issues from the skull. Whether it really belongs to the 

 facial proper has been doubted ; in man the fibres which form it are 

 either fibres coming not from the roots of the facial proper but from 

 the portio intermedia Wrisbergi, or, according to some, fibres 

 which though joining the facial in the Fallopian canal are ulti- 

 mately derived from another (the fifth) cranial nerve. Leaving 

 the facial nerve the chorda tympani passes through the tympanic 

 cavity or drum of the ear (hence the name) and joins or rather 

 runs in company (ch.t 1 ) with the lingual or gustatory branch of the 

 fifth nerve. Some of the fibres run on with the lingual right down 

 to the tongue (these are not shewn in the figure), but many leave 

 the lingual as a slender nerve (ch.t), which reaching Wharton's 

 duct or duct of the submaxillary gland (sm.d) runs along the duct 

 to the gland. As the nerve courses along the duct nerve cells make 

 their appearance among the fibres, and these are especially abun- 

 dant just after the duct enters the hilus of the gland. The fibres 

 may be traced into the gland for some distance, but as we have 

 said their ultimate ending has not yet been definitely made out. 

 Along its whole course up to the gland, the fibres of the chorda 

 are very fine medullated fibres, but they lose their medulla in 

 the gland. 



The other set of nerve-fibres reaches the gland along the small 

 arteries of the gland. These are non-medullated fibres mixed with 

 a few medullated fibres and may be traced back to the superior 

 cervical ganglion. From thence they may be traced still further 

 back down the cervical sympathetic to the spinal cord, following 

 apparently the same tract as the vaso-constrictor fibres, treated of 

 in 166. 



226. If a tube be placed in the duct, it is seen that when 

 sapid substances are placed on the tongue, or the tongue is 

 stimulated in any other way, or the lingual nerve is laid bare and 

 stimulated with an interrupted current, a copious flow of saliva 

 takes place. If the sympathetic be divided, stimulation of the 

 tongue or lingual nerve still produces a flow. But if the small 

 chorda nerve be divided, stimulation of the tongue or lingual nerve 

 produces no flow. 



Evidently the flow of saliva is a nervous reflex action, the 

 lingual nerve serving as the channel for the afferent and the small 

 chorda nerve for the efferent impulses. If the trunk of the 

 lingual be divided above the point where the chorda leaves it, as 



