20 Feeds and Feeding. 



Pood requires from three to four days to pass through the 

 whole digestive tract of farm animals. The last traces do not 

 pass until considerably later. According to "Weiske,* it takes 

 from seven to eight days before the last traces pass the digestive 

 canal in case of the sheep. (541) 



33. The intestinal juice. — The juices secreted by the small 

 glands along the inner walls of the small intestine contain three 

 ferments which act upon starch, cane sugar and protein. Starch 

 is readily converted into sugar by the intestinal juice in a neu- 

 tral or faintly alkaline solution. The juice further contains a 

 special ferment which changes cane sugar into glucose and 

 laevulose. 



34. Fermentations. — Numerous organisms which find their way 

 into the small intestine along with food substances give rise to 

 fermentations, causing the evolution of various gases, mainly air, 

 carbonic acid, hydrogen, ammonia, sulfaretted hydrogen and 

 marsh gas. 



35. Absorption. — The stomach and intestines form a convoluted 

 tube passing through the body. Pood materials within this tube 

 are stUl outside the body. The entrance of digestion products 

 into the body is brought about by absorption, which is of two 

 kinds. The inner walls of the digestive tract are everywhere 

 lined with blood vessels, and substances soluble in water and 

 readily diffusible, such as sugar, soaps, salts and peptones, enter 

 the blood by diffosion. 



The inner surface of the small intestine is also lined with cone- 

 like projections called "villi." The cells of these villi separate 

 from the fluid contents of the intestines, sugar, fat, peptones, 

 salts and other materials, and deliver them into ducts of the 

 lymphatic system, by which they are carried forward toward the 

 heart, to be mingled with the blood. The material drawn into 

 the lymphatics by the villi is called chyle, a substance having a 

 nulky appearance owing to the fat held in suspension. The fat in 

 the chyle of a horse may vary from 1 per cent, when fed on hay, 

 to 3 per cent, when fed on oats. The composition of chyle is 

 given in the table on the next page. 



^ Journal f. Landw., 1878, p. 175. 



