2 5 



ANIMAL BIOLOGY 



the contraction of the muscular walls that forces along the 

 food. The inner surface of the small intestine is thrown 

 into many folds, and these are beset with numerous minute 



FIG. 190. FIG. 191. 



FIG. 190. Gland of stomach. M, mucus forming cells; C, chief cells; 



P, parietal cells. 

 FIG. 191. Part of small intestine cut open to show folds in lining. 



finger-like projections called mill whose function it is to 

 increase the surface available for absorption. The villi 



are richly supplied with blood 

 and lymph vessels which carry 

 away the soluble food materials 

 absorbed from the intestines: 



The small intestine leads to 

 the large intestine. Near the 

 point where the latter begins 

 there is a short pocket, the c&cum, 

 at the end of which is a small 

 tubular organ, the vermiform ap- 

 pendix. Whatever may be the 

 function of the latter organ it is 

 often the seat of inflammation 

 (appendicitis) which frequently 

 necessitates an operation for the removal of the offending 

 part. 



Two large and important glands, the pancreas and the 

 liver, pour their secretions by a short common duct into the 

 small intestine. The pancreas secretes an alkaline fluid, 



FIG. 192. Villi, v, of small 

 intestine; c, capillaries of 

 blood vessels; gl, gland; /, 

 lacteals or lymph vessels. 



