DIGESTION AND ABSORPTION 



297 



This is done by the enzymes which cause digestion. It will be the 

 purpose of this chapter to discover where and how digestion takes 

 place in our own body. 



Alimentary Canal. — In all vertebrate animals, including 

 man, food is taken in the mouth and passed through a food tube 

 in which it is digested. This tube is composed of different por- 

 tions, named, respec- q « 



tively, as we pass from 

 the mouth downward, 

 the gullet, stomach, 

 small and large intes- 

 tine, and rectum. 



Comparison of Food 

 Tube of a Frog and 

 Man. — If we compare 

 the food tube of a dis- 

 sected frog with the 

 food tube of man (as 

 shown by a manikin or 

 chart), we find part for 

 part they are much the 

 same. But we notice 

 that the intestines of 

 man, both small and 

 large, are relatively 

 longer than in the frog. 

 We also notice in man the body cavity or space in which the 

 internal organs rest is divided in two parts by a wall of muscle, 

 the diaphragm, which separates the heart and lungs from the 

 other internal organs. In the frog no muscular diaphragm exists. 

 In the frog we can see plainly the silvery transparent mesenkry 

 or double fold of the lining of the body cavity in which the organs 

 of digestion are suspended. Numerous blood vessels can be found 

 especially in the walls of the food tube. 



Glands. — In addition to the alimentary canal projicr, wo find a 

 number of digestive glands, varying in size and position, connected 

 with the canal. 



FROG 



MAN 



The digestive tract of the frog and man. Gul, gullet ; 

 S, stomach; L, liver; G, gall bladder; P, pancreas; 

 Sp, spleen ; SI, small intestine ; LI, large in- 

 testine ; V, appendix; .-1, anus. 



