THE FECES 



393 



overestimated. Indol and skatol undergo oxidation in the liver after ab- 

 sorption, forming indoxyl and skatoxyl. They are in part carried off in the 

 feces, but when the bowel is obstructed they are absorbed and eventually 

 appear in the urine, indoxyl and skatoxyl forming, respectively, indoxyl- 

 and skatoxyl-sulphuric acids and their salts. Tyrosin is broken down into 

 para-oxy-phenol-propionic acid, paracresol, and phenol; para-oxy-phenol- 

 acetic acid is also formed. The phenols, after absorption, are in part con- 

 jugated with glycuronic acid which is formed by the incomplete oxidation 

 of dextrose and are eliminated into the urine. Experiments have been per- 

 formed to determine whether or not the intestinal bacteria are necessary to 

 normal digestion. The weight of evidence is in favor of the view that they 

 are not. 



The Feces. The contents of the large intestine, as they proceed toward 

 the rectum, become more and more solid, lose more liquid and nutrient 

 parts, and gradually acquire the odor and consistency characteristic of 

 feces. 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 opening the 

 bowels, or defecation. The average quantity of matter evacuated by the 

 human adult in twenty-four hours is about 200 to 250 grams, but the amount 

 and character vary exceedingly according to the food eaten. Vegetable foods 

 contain much indigestible matter, while meats and meat diets leave very 

 little unabsorbed material to be expelled 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 733 



Solids, comprising: 



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



woody fibers, cartilage, horny matter, mucin, seldom 

 muscular fibers and other proteins, fat, and cholesterin . 



b. Certain substances resulting from decomposition of foods, 



such as indol, skatol, fatty and other acids ; calcium and 

 magnesium soaps 



c. Special excretion, excretin, excretoleic acid (Marcet), 



and stercorin (Austin Flint) 



d. Salts chiefly phosphate of magnesium and phosphate [-267 



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 the 



secretions 



1000 



