Chap. XIV] 



THE DIGESTIVE SYSTEM 



257 



The palate, uvula, palatine arches, and tonsils are plainly seen 

 if the mouth is widely opened and the tongue depressed. 



The fauces is the name given to the aperture leading from the 

 mouth into the pharynx, or throat cavity. 



The tongue. — The tongue ^ is the special organ of the sense of 

 taste and assists in speech. It has also to be considered with ref- 

 erence to digestion, (1) because stimulation of the nerves of the 

 sense of taste start the secretion of digestive juices, (2) it assists in 

 swallowing, and (3) the follicles at the back of the tongue secrete 

 mucus, which lubricates the food and makes swallowing easier. 



The salivary glands. — The mucous membrane lining the 

 mouth contains many minute glands consisting of just one cell. 

 These are called goblet cells and pour their secretion upon its 

 surface, but the chief 

 secretion of the mouth 

 is supplied by the 

 salivary glands, which 

 are three pairs of com- 

 pound saccular glands 

 called the parotid, sub- 

 maxillary, and sub- 

 lingual, respectively. 

 Each parotid gland is 

 placed just under and 

 in front of the ear ; its 

 duct passes forward 

 along the cheek, until 

 it opens into the in- 

 terior of the mouth 

 opposite the second 

 molar tooth of the 

 upper jaw. The submaxillary and sublingual glands are situ- 

 ated below the jaw and under the tongue, the submaxillary 

 being placed further back than the sublingual. Their ducts open 

 in the floor of the mouth beneath the tongue. The secretion of 

 these salivary glands, mixed with that of the small glands of the 

 mouth, is called saliva. 



The teeth. — The semicircular borders of the upper and lower 



Fig. 148. — The Salivary Glands. 



' A detailed description of the tongue will be found in Chapter XX. 

 B 



