CHAPTER VII. 



MOUTH DIGESTION. 



FIG. 60. 



THE cavity of the mouth is lined by a bright red raucous mem- 

 brane, which is continuous with the skin at the lips. It varies 

 in structure in different parts of the buccal cavity, and in its gen- 

 eral construction more resembles the outer covering of the body 

 than the mucous membrane lining the alimentary tract. It con- 

 sists of (1) a superficial part composed of thick stratified epithe- 

 lium, the upper cells of which are flat, scaly, and tough, and 

 are placed horizontally, while in the deeper ones the cells are 

 soft, rounded or elongated, having 

 their long axis perpendicular to 

 the surface ; and (2) a deeper part 

 composed of fibro-elastic tissue, 

 which, over the alveoli of the 

 teeth, is amalgamated with the 

 periosteum and forms the dense 

 tough gums. 



The mucous membrane of the 

 mouth is covered with papillae, 

 which on thedorsum of the tongue 

 attain great magnitude and va- 

 riety of shape and epithelial cov- 

 ering. In man, three kinds are 



described: (1.) Narrow pointed, jWi/orro. (2.) Blunt and clubbed 

 at the apex, fungiform. (3.) Broad complex papillae, surrounded 

 by a fossa, circumvallate, of which there are but a limited num- 

 ber (about a dozen). 



The special secreting organs or glands, which pour their juices 

 into the mouth, have all the same general type of structure, 

 though they vary much in the detail as to the variety and char- 

 acter of their cells. They are known as the acinous or sacculated 



Diagram taken from a small 

 portion of sacculated gland from 

 Cockroach, showing branching 

 duct and saccules. 



