22 Feeds and Feeding. 



relaxes and allows a small quantity of the semi-liquid contents of 

 the stomach to spurt thru into the intestine. After this the ring 

 of muscles again contracts, thereby closing the entrance. The stom- 

 ach in turn slowly relaxes, and after a certain length of time, vary- 

 ing in different animals, the process is repeated. By this means the 

 fluid portions of the mixed contents of the stomach are squeezed out 

 and carried into the small intestine, while the more solid portions 

 remain behind for further action by the gastric juice. 



32. The stomach of ruminants. In such animals as the horse the 

 gullet is a simple muscular tube passing from the mouth to the 

 stomach. In ruminants, or animals which chew the cud, as the 

 cow, sheep, etc., it is expanded into three compartments of great 

 aggregate capacity, called the paunch, the honeycomb, and the 

 manyplies, before the true stomach is reached. They secrete water 

 but no enzymes, and merely serve as pouches for the storage of 

 food and the better preparation of it for digestion. With rumi- 

 nants the food is swallowed after partial mastication and passes to 

 the paunch, from which it can be returned to the mouth in small 

 portions to be again chewed. While the food is in any of the first 

 compartments the action of the ptyalin of the saliva continues. 



The nutritive substances within the cells of plants are enclosed 

 within the cellulose cell walls. Where these cell walls are formed 

 of hard, thickened cellulose, the nutritive substances contained 

 within the cells are not readily reached by the fluids of digestion. 

 In the first stomachs of ruminants, especially in the paunch, the fer- 

 mentation of cellulose by bacteria takes place, the walls of the 

 cells being thereby more or less broken down and their contents 

 set free, thus becoming available for digestion. In the partial de- 

 struction of the woody cellulose in the paunch there regularly oc- 

 curs the evolution of gases, which may be very considerable when 

 fresh, easily fermentable forage, such as green clover or alfalfa, is 

 eaten. Ordinarily these gases are absorbed by the blood, but in 

 some cases the gas is evolved so rapidly that the blood circulation 

 cannot absorb it as fast as formed, and hoven or bloat occurs. 



33. The small intestine. In the small intestine the work of di- 

 gestion is carried on even more vigorously than in the stomach. All 

 classes of nutrients are attacked by the fluids it holds, and in it the 

 digestive processes come to a close. The contents of the stomach, 

 when received into the small intestine, consist of a semi-liquid mix- 

 ture of undigested proteins, partially digested nutrients proteoses 

 and peptones, fats, sugars, starches, and celluloses and waste mat- 



