480 THE SALIVAR Y GLANDS. 



gland ducts, and accompanies them into the glands. Other fine 

 filaments, coming from the chorda tympani proper, are given off from 

 both sides of the lingual, as it runs forward over the sublingual 

 gland ; most of these end in this gland, but a few fibres, varying in 

 number in different animals, run back and supply the submaxillary 

 gland. Finally, a few fibres, from the chorda tympani proper, con- 

 tinue their course in the lingual, and supply the glands and blood 

 vessels in the area of distribution of the lingual nerve in the tongue. 



On the course of the nerve filaments to the glands are a number 

 of small and often microscopic ganglia. In the smaller filaments these 

 begin a very short distance from the lingual nerve, and then occur at 

 intervals as far as the terminations of the ducts. Fibres from the 

 filaments and ganglia intermingle, ami form a plexus ; this plexus, at 

 first, overlies the sublingual gland, but, further on, surrounds and 

 accompanies the ducts, chiefly those of the sublingual gland. The 

 larger part of the chorda tympani passes by this plexus, and runs 

 direct to a ganglion in the hilus of the submaxillary gland ; where the 

 duct begins to divide, this ganglion gives off strands, which form 

 another plexus, surrounding and accompanying the divisions of Whar- 

 ton's duct. 



Some of the ganglia in the plexus over the sublingual gland are 

 relatively large ; thus in the dog there is, as a rule, a ganglion, which 

 may be seen with the eye, in the angle between the lingual and 

 the chorda tympani. This was called, by Bernard, the submaxillary 

 ganglion ; as we shall see presently, it is more appropriate to call it 

 the sublingual ganglion. Another, and a larger ganglion, is that 

 spoken of above, as present in the submaxillary gland. As this belongs 

 chiefly, if not entirely, to the submaxillary gland, we may call it the 

 submaxillary ganglion. But it must be remembered that the nerve- 

 cells which occur on the course of the chorda tympani fibres, either to 

 the sublingual or to the submaxillary gland, are not collected together 

 in a single ganglion, but occur scattered at intervals on the nerve- 

 plexus into which the fibres run. 



The nerve-cells are on the course, both of the secretory and of the 

 vaso-dilator fibres of the chorda tympani. This may be shown by 

 stimulating the chorda tympani, centrally of the nerve-cells, and 

 peripherally of them, before and after injecting nicotine into a vein. 1 

 The experiment is best made in a cat. Normally, stimulation of the 

 chorda tympani, in any part of its course, causes a flow of saliva, and an 

 increased blood flow from the gland vein. After injecting a small dose 

 of nicotine into a vein (cf. p. 515), stimulation of the chorda tympani in 

 the tympanic cavity, or of the chordo-lingual nerve, has no effect. But 

 a rapid secretion, and a greatly increased blood flow from the gland vein 

 in fact, the usual effects of stimulating the chorda tympani are 

 readily obtained by stimulating the nerve plexus in the hilus of the 

 gland. Since no nerve except the chorda tympani is able to produce 

 these effects, we may safely conclude that, in stimulating the nerve- 

 plexus in the hilus of the gland, it is the peripheral chorda tympani 

 fibres which cause the secretion and increased blood flow. The amount 

 of nicotine given does not prevent nor, so far as we know, affect the 

 passage of a nervous impulse along a nerve-fibre, and, in consequence, 

 we conclude that the nerve-cells are on the course of the chorda 



1 Langley, Journ. Physiol., Cambridge and London, 1890, vol. xi. p. 123. 



