CONSTITUENTS OF FOOD. 89 



to be fully supplied with water in order that it may secrete a 

 sufficiency of digestive juices. Consequently we should give a 

 horse as much water as he chooses to drink before feeding 

 him. 



ABSORPTION. 



As the absorbents are separated from the contents of the 

 intestines by only a thin membrane, they readily take up 

 water, digested food and dissolved salts, and convey them into 

 the blood after having passed them through the liver and 

 other glands, which produce changes in the food that are 

 necessary for rendering it capable of being utilised by the 

 body. The absorption of digested food begins in the small 

 intestine and is completed in the large one, a certain amount 

 of water and dissolved salts being absorbed in the stomach. 

 The absorbed food may be regarded as that which is taken up 

 by the tissues (assimilated) ; and that which, being apparently 

 in excess of the requirements of the system, is passed out of it 

 without undergoing change. Thus, egg albumen is often 

 present in the urine of human beings who have recently eaten 

 large quantities of such albumen. Also, common salt is found 

 in the perspiration of horses and men ; and when water has 

 been drunk in excess, an increased discharge of urine generally 

 takes place. 



NUTRITIVE AND DIGESTIVE FUNCTIONS OF THE 

 CONSTITUENTS OF FOOD. 



Water, whether drunk by the horse or whether it forms a 

 constituent of his food, is evidently necessary for the repair of 

 broken-down tissue, and for maintaining the blood and other 

 fluids of the body in a properly diluted condition, especially 

 when we consider that water forms about three-quarters of the 

 entire weight of the adult horse, and that a large quantity of 

 water is given off by the lungs, skin, and kidneys. The 



