18 



APPLIED PHYSIOLOGY 



so as to be able to judge of the position of the food and to 



tell when it is chewed enough. 



23. Mucous membrane. The mouth, as well as every 



other cavity of the body, 

 a has a thin lining called 

 mucous membrane, which 

 looks like a fine, soft skin. 

 At the lips, nose, and other 

 openings, this lining joins 

 the skin so that it is im- 

 possible to tell where the 

 one begins and the other 

 ends. It is really a part 

 of the skin turned inside 

 the body. Mucous mem- 

 brane is made of a net- 

 work of cells and fibers, 

 which is covered with an 

 unbroken layer of firm 

 cells called egithelimn. __ 

 24. Glands. In each 

 mucous membrane are 

 tiny tubes which open 

 upon its surface. Each 

 tube is lined with cells 



b the epithelium continued into a simple tube, of epithelium like those 

 c the epithelium continued into a simple ' . r r , 



p OC k eL upon the surface of the 



d the epithelium continued into a series of membrane. The Cells 



branching tubes and pockets. . . . , , , 



. c, and d are glands. lmmg each tube produce 



a slightly slimy fluid 



called *ui(fue They pour just enough of it upon the 

 surface of the membrane to moisten it. 



A tube or collection of tubes whose cells can form a 



Diagram of glands. 



the surface of a mucous 



