DIGESTIVE FLUIDS. 



97 



tipper jaw. The submaxillary gland, about the size of a 

 large prune, lies beneath the lower jaw, and its duct the 

 duct of Wharton opens under the tongue. The termination 

 of this duct, along with its fellow, may be seen in a looking- 

 glass, making a little swelling on the lower part of the 

 frsenum or bridle of the tongue. At the same time will be 

 seen on each side of the frsenum, between the tongue and 

 the jaw, an eleva- 

 tion about the size \ 

 of an almond, with 

 the outlines of the 

 sublingual gland 

 seen through the 

 mucous membrane. 

 It has several 

 ducts, some of 

 which open separ- 

 ately, while others 

 fall into Wharton's 

 duct. Besides these 

 large glands, there 

 are numerous others 

 of small size which 

 open into the 

 mouth, particularly 



the buccal glands, Fig. 53. SALIVARY GLANDS, a, parotid; 6, 

 a series of struc- submaxillary; c, sublingual. 



tures the size of lentils, scattered under the mucous 

 membrane of the lips and cheeks, and a smaller set of glands 

 near the tip of the tongue; but they are engaged in the 

 secretion of a mucus which has little or nothing to do with 

 digestion. The saliva has a slightly alkaline reaction, and 

 its most important ingredient, besides water, is a nitrogenous 

 substance called ptyalin which has in a very high degree the 

 property of converting starch into grape-sugar, provided that 

 the solution be alkaline. So powerful is this action, that a 

 notable amount of the starch taken into the mouth as food 

 is converted into dextrin or sugar before being swallowed; 

 and when the food is of a tenacious consistence, masticated 

 and taken in quantity, a large part of it may escape for a 

 14 G 



