30 Feeds and Feeding. 



which are mostly toxic or poisonous to the animal result in small 

 quantity from bacterial growth in the large intestine. To these 

 substances the odor of the feces is largely due. If the functions 

 of the bowels are impaired, the contents may remain for an undue 

 length of time, in which case excessive putrefaction may cause the 

 animal to suffer from poisoning due to the absorption of the prod- 

 ucts formed. 



44. Feces. — The solid excrement, or dung, of farm animals is 

 that waste which finally escapes from the large intestine, the solids 

 of which, for the most part, have never been within the body 

 proper. It is composed principally of cellulose, or woody fiber, 

 from the undigested portions of straw, hay, and grasses ; and also 

 of seeds, grains, or parts of the food that have escaped proper mas- 

 tication and digestion. Matter not properly food, such as hair and 

 dirt of various kinds taken into the alimentary tract, escapes thru 

 this exit. Finally there are cast away traces of bile salts and some 

 mucus from the lining of the intestines, together with much water. 



45. Amid digestion.— The nitrogenous bodies of plants which 

 are known collectively as "amids" are, as before stated, simpler 

 nitrogenous compounds than proteins. They are either on their 

 way to be built into proteins, or result from the cleavage of pro- 

 teins in the plant for the purposes of transportation, or are formed 

 in the partial breaking down and decay of protein. Very little is 

 actually known of their chemical nature, but they are probably 

 similar in character, in many instances at least, to certain inter- 

 mediary products of digestion in the animal body. Since amids 

 may result from enzyme action in the plant, their digestion in the 

 animal may be looked upon as similar to that of proteins. 



46. Mineral matter. — So far as known, the mineral matter, or 

 ash, in foods is absorbed principally from the small intestine and 

 is usually unchanged in chemical composition. Changes which 

 occur in the different inorganic salts, or mineral matter, are en- 

 tirely due to such chemical reactions as would have taken place 

 outside the intestine under the same conditions. Insoluble mineral 

 matter in food may become soluble because of the hydrochloric 

 acid in the gastric juice of the stomach, but this is hardly to be re- 

 garded as digestion, 



47. The work of the digestive glands. — The brilliant studies of 

 the Russian physiologist, Pawlow,^ and his associates, working with 

 dogs, have thrown much light upon the subjects of digestion, appe- 



' Tte Work of the Digestive Glands. 



