CHAP, i.] TISSUES AND MECHANISMS OF DIGESTION. 421 



at n.l', Fig. 62, stimulation of the (front part of) tongue produces, 

 under ordinary circumstances, no flow. This shews that the centre 

 of the reflex action is higher up than the point of section ; it lies 

 in fact in the brain. 



ch.f 



FIG. 62. DIAGRAMMATIC KEPRESENTATION OF THE SUBMAXILLARY GLAND OP THE DOG 

 WITH ITS NERVES AND BLOOD VESSELS. 



(The dissection has been made on an animal lying on its back, but since all the 

 parts shewn in the figure cannot be seen from any one point of view, the figure 

 does not give the exact anatomical relations of the several structures.) 



sm.gld. The submaxillary gland, into the duct (sm.d. ) of which a cannula has 

 been tied. The sublingual gland and duct are not shewn, n.l. , n.l'. The lingual 

 branch of the fifth nerve, the part n.l. is going to the tongue, ch.t. , ch.t'., ch.t". 

 The chorda tympani. The part ch. t". is proceeding from the facial nerve ; at ch.t'. 

 it becomes conjoined with the lingual n.l'. and afterwards diverging passes as ch.t. 

 to the gland along the duct ; the continuation of the nerve in company with the 

 lingual n.l. is not shewn. sm.gl. The submaxillary ganglion with its several 

 roots, a. car. The carotid artery, two small branches of which, a.sm.a. and r.sm.p., 

 pass to the anterior and posterior parts of the gland, v.s m. The anterior and pos- 

 terior veins from the gland, falling into v.j. the jugular vein, v.sym. The con- 

 joined vagus and sympathetic trunks, gl.cer.s. The upper cervical ganglion, two 

 branches of which forming a plexus (a./.) over the facial artery, are distributed 

 (n.sym.sm.) along the two glandular arteries to the anterior and posterior portions 

 of the gland. 



The arrows indicate the direction taken by the nervous impulses during reflex 

 stimulation of the gland. They ascend to the brain by the lingual and descend by 

 the chorda tympani. 



In the angle between the lingual and the chorda, where the latter 

 leaves the former to pass to the gland, lies the small submaxillary gan- 

 glion (represented diagrammatically in Fig. 62 sm. gl.). This consists 

 of small masses of nerve cells lying on the small bundles of nerve fibres 

 which spread out like a fan from the lingual and chorda tympani 



