4 8o THE SALIVAR Y GLANDS. 
glaud 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, and form a plexus; this plexus, at 
first, overlies the sublingual gland, but, further on, surrounds and 
accompanies tin 1 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 sinsle o;an£dion, 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, Joum. Physiol., Cambridge and London, 1890, vol. xi. p. 123. 
