238 HANDBOOK OF PHYSIOLOGY. 



A. On the Submaxillary Gland. The submaxillary gland has been 

 the gland chiefly employed for the purpose of experimentally demon- 

 strating the influence of the nervous system upon the secretion of saliva, 

 because of the comparative facility with which, with its blood-vessels and 

 nerves, it may be exposed to view in the dog, rabbit, and other animals. 

 The chief nerves supplied to the gland are: (I) the chorda tympani, a 

 branch given off from the facial (or portio dura of the seventh pair of 

 nerves), in the canal through which it passes in the temporal bone, in its 

 passage from the interior of the skull to the face; and (2) branches of 

 the sympathetic nerve from the plexus around the facial artery and its 

 branches to the gland. The chorda (Fig. 178, ch. t.), after quitting the 

 temporal bone, passes downwards and forwards, under cover of the ex- 

 ternal pterygoid muscle, and joins at an acute angle the lingual or gus- 

 tatory nerve, proceeds with it for a short distance, and then passes along 

 the submaxillary gland duct (Fig. 178, sm. d.), to which it is distributed, 

 giving branches to the submaxillary ganglion (Fig. 178, sm. gl.)\ and 

 sending others to terminate in the superficial muscles of the tongue. If 

 this nerve be exposed and divided anywhere in its course from its exit 

 from the skull to the gland, the secretion, if the gland be in action, is 

 arrested, and no stimulation either of the lingual or of the glosso-pharyn- 

 geal will produce a flow of saliva. But if the peripheral end of the di- 

 vided nerve be stimulated, an abundant secretion of saliva ensues, and 

 the blood-supply is enormously increased, the arteries being dilated. The 

 veins even pulsate, and the blood contained within them is more arterial 

 than venous in character. 



When, on the other hand, the stimulus is applied to the sympathetic 

 filaments (mere division producing no apparent effect), the arteries con- 

 tract, and the blood stream is in consequence much diminished ; and 

 from the veins, when opened, there escapes only a sluggish stream of 

 dark blood. The saliva, instead of being abundant and watery, becomes 

 scanty and tenacious. If both chorda tympani and sympathetic branches 

 be divided, the gland, released from nervous control, secretes continuously 

 and abundantly (paralytic secretion). 



The abundant secretion of saliva, which follows stimulation of the 

 chorda tympani, is not merely the result of a filtration of fluid from the 

 blood-vessels, in consequence of the largely increased circulation through 

 them. This is proved by the fact that, when the main duct is obstructed 

 the pressure within may considerably exceed the blood-pressure in the 

 arteries, and also that when into the veins of the animal experimented 

 upon some atropin has been previously injected, stimulation of the peri- 

 pheral end of the divided chorda produces all the vascular effects as be- 

 fore, without any secretion of saliva accompanying them. Again, if an 

 animal's head be cut off, and the chorda be rapidly exposed and stimu- 

 lated with an interrupted current, a secretion of saliva ensues for a short 



