294 



PHYSIOLOGY OF THE DOMESTIC ANIMALS. 



that the quantity of saliva poured out varies under many different circum- 

 stances, as to the character of the food, and the side on which masti- 

 cation is taking place. It might be already concluded from this, that 

 the secretion of saliva is a reflex action and is under the control of the 

 nervous system. As long ago as 1832 Mitscherlich, from studies made 

 on a patient with a salivary fistula, first suggested that the salivary 

 secretion was under the influence of the nervous system, and in support 

 of that statement alluded to the fact that while the secretion of saliva 

 was independent of the will, it might be called forth by stimulation of 

 the mucous membrane of the tongue and mouth, either chemically or' 



Fig. 119.— Nerves of Submaxillary and Sublingual Glands. {Bernard.) 



a, submaxillary gland; c c, duct of Wharton; ihg, arterial branches to the submaxillary gland; 

 6, sublingual gland: d d, sublingual duct; 1 1. lingual nerve; 2 2, chorda tympani : ^.carotid artery, on 

 which ramify b'bres coming from the superior cervical ganglion ; /, internal maxillary artery. 



mechanically, stimulation of the nerve of smell, or stimulation of the 

 gastric mucous membrane by the food. It thus is clear that the secretion 

 of saliva is a reflex action, for which there must be an afferent fibre, 

 an independent nerve centre, and an efferent fibre. From the fact that 

 the submaxillary gland is the most exposed, and, therefore, the most 

 readily operated on, the influence of the nerves on the secretion of 

 saliva has been most studied in the case of this gland. The afferent 

 nerve fibres of this reflex circle, in the case of the submaxillary gland, 

 are the lingual branch of the fifth pair and branches of the glosso- 



