348 



FOOD AND DIGESTION 



parts, and gradually acquire the odor and consistency characteristic of jeces. 

 After a sojourn of uncertain duration in the sigmoid flexure of the colon, or 

 in the rectum, they are finally expelled by the act of defecation. The average 

 quantity of solid matter evacuated by the human adult in twenty-four hours 

 is about 200 to 250 grams, but the amount and character vary exceedingly ac- 

 cording to the food eaten. Vegetable foods contain much indigestible matter, 

 while meats and meat diets leave very little unabsorbed material to be ex- 

 pelled in the feces. 



TABLE OF COMPOSITION OF FECES. 



The amount of water varies considerably, from 68 to 82 per cent and 

 upward. The following table gives about an average composition: 



Water 



Solids, comprising: 



a. Insoluble residues of the food, uncooked starch, cellulose, 



woody fibers, cartilage, horny matter, mucin, seldom mus- 

 cular fibers and other proteids, fat, and cholesterin ...... 



b. Certain substances resulting from decomposition of foods, 



indol, skatol, fatty and other acids; calcium and mag- 

 nesium soaps ..................................... 



c. Special excretions, Excretin, excretoleic acid (Marcet), 



and stercorin (Austin Flint) .......................... 



d. Salts, Chiefly phosphate of magnesium and phosphate 



of calcium, with small quantities of iron, soda, lime, and 

 silica ............................................ 



e. Insoluble substances accidentally introduced with the food 



f. Mucus, epithelium, altered coloring matter of bile, fatty 



acids, etc ......................................... 



g. Varying quantities of other constituents of bile and secre- 



tions . . ............... 



733- 



267.00 



Intestinal Gases. Under ordinary circumstances, the alimentary ca- 

 nal contains a considerable quantity of gases. The presence of gas in the 



0000006 



FIG. 277. Diagram Illustrating the Segmentation of the Food in the Small Intestine. (Cannon.) 



intestines is so constant and the amount in health so uniform that there can 

 be no doubt that its existence is a normal condition. 



The gas contained in the stomach and bowels is from air swallowed with 



