118 THE FEEDING OF ANIMALS 



THE FECES 



The soluble and insoluble portions of the intestinal 

 contents become separated gradually, and the undissolved 

 part arrives finally at the last stage of its journey along 

 the alimentary canal, and is expelled as the solid excre- 

 ment, or feces. 



173. Constituents of feces. The feces is made up of 

 the undigested food, residues from the bile and other 

 digestive juices, mucus, and more or less of the epithelial 

 cells which have become detached from the walls of the 

 stomach and intestines. Dead and living bacteria also 

 appear to constitute a material portion of the fecal mat- 

 ter. These organisms are not taken in with the food to 

 any great extent, but are the result of their continuous 

 growth in the digestive tract. Small quantities of fer- 

 mentation products, particularly indol and skatol, are 

 present, which give to the feces its offensive odor. The 

 incidental or .waste products may properly be considered 

 as belonging to the wear and tear of digestion. 



174. The feces not wholly undigested food. The 

 ordinary conception of the fecal residue is that it is only 

 the part of the food that has resisted the action of the 

 digestive fluids, but in fact it is much more than that. Not 

 only does it include the various waste products previ- 

 ously referred to, but also compounds that have been 

 absorbed into the blood circulation and returned to the 

 alimentary canal for excretion. It has been shown, for 

 instance, that when a phosphorus compound was in- 

 jected subcutaneously into a sheep, the phosphorus was 

 excreted in the feces in another combination. It is also 

 proven that mineral compounds absorbed from the intes- 

 tinal tract may afterward appear in the feces. 



