162 DIGESTION. 



during mastication there exists a difference in the pressure 

 of the muscles or of the condyles on the two sides, corre- 

 sponding with the di-fferences which have been noted in the 

 secretion from the glands on either side. In the horse and 

 in the dog, it has been observed that the secretion of the paro- 

 tids is completely arrested during the deglutition of liquids, 

 while the flow from the other salivary glands is not affected. 1 



To sum up the functions of the parotid saliva, aside 

 from any chemical action which it may have upon the food, 

 which will be fully considered in connection with the mixed 

 saliva, it evidently has an important mechanical office. It 

 is discharged in large quantity during the entire process of 

 mastication, and is poured into the mouth in such a manner 

 as to become of necessity thoroughly incorporated with the 

 food. Its function is chiefly, though not exclusively, connect- 

 ed with mastication, and indirectly with deglutition ; for it 

 is only by becoming incorporated with this saliva, that the 

 deglutition of dry pulverulent substances is rendered possible. 

 Facts in comparative physiology, showing a great development 

 of the parotids in animals that masticate very thoroughly, 

 particularly the ruminants, a slight development in those 

 that masticate but slightly, and the absence of these glands in 

 animals that do not masticate at all, 2 are additional arguments 

 in favor of these views. 



Su~bmaxillary Saliva. In the human subject, the sub- 

 maxillary is the second of the salivary glands in point of size. 

 Its minute structure is the same as that of the parotid. As 

 its name implies, it is situated below the inferior maxillary 

 bone, and is found in the anterior part of what is known as 

 the submaxillary triangle of the neck. Its excretory duct, 

 called sometimes the duct of Wharton, is about two inches 



1 BERNARD, op. dt., p. 52. 



3 MILNE-EDWARDS, Legons sur la Physiologic et V Anatomic Comparee, Paris, 

 1859, tome vi., p. 239. 



