DIGESTION 



75 



To increase the surface that can produce such fluids, 

 the mucous membrane may become folded up in va- 

 rious ways, giving rise to the different kinds of glands. 

 While the glands differ much in their outward appear- 

 ance and size, all 

 have the same 

 general structure 

 and all take ma- 

 terial from the 

 blood to manufac- 

 ture important 

 body fluids which 

 perform special 

 functions. 



The important 

 thing to remem- 

 ber is that a gland 

 is merely a thick 

 mucous m em- 

 brane, either 

 straight or folded 

 in some way, con- 

 taining many 

 blood vessels and 



FJG. 36. Showing the structure of glands. 

 Modified from Huxley. (Zinns.) 



nerves, and hav- 

 ing the power to 

 separate from the blood important fluids called secretions. 

 67. The Mouth. The mouth is the first organ to 

 receive the food. It is a rather irregular-shaped cavity 

 extending from the lips in front to the soft palate be- 



