21 Feeds and Feeding. 



Horse. Cow. Pig. 



Urea 31.0 18.5 4.9 



Potass. Mppurate 4.7 16.5 0.0 



Alkaline lactates 20.1 17.2 



Potass, bicarb 15.6 16.1 10.7 



Mag. carb 4.2 4.7 0.9 



Calcium carb 10.8 0.6 traces. 



Potass, sulph 1.2 3.6 2.0 



Sodium chlorid 0.7 1.5 1.3 



Silica 1.0 traces. 0.1 



Phosphates 0.0 0.0 1.0 



Water and undetermined substances 910.0 921.3 979.1 



1000.00 1000.00 1000.00 



41. Composition of urine. — The leading characteristic of urine 

 is urea, which is the product of the decomposition of the albu- 

 minoid substances or tissues of the animal body. The other means 

 of escape for this waste are so small that by measuring the nitrogen 

 in the urine the nitrogenous waste of the body can be very closely 

 determined, — a fact of the highest importance. (57) Most of 

 the potash taken from the food passes away in the urine, while 

 only a small amount of phosphates is contained thereiu. (419) 



42. Excretions of the skin. — "Water passes off through the 

 sweat glands of the skin, carrying a very small per cent, of solids. 

 The moistiu'e given off by the sweat glands of a man is placed at 

 from one to two pounds daily, although it may be increased to 

 five pounds. The perspiration of animals has not been deter- 

 mined. Carbonic acid gas and traces of ammonia and free 

 nitrogen are also given off by the skin. 



43. Protein nutrition. — The nitrogenous substances of the food, 

 as we have seen, are converted into soluble peptones, which are 

 taken up by absorption, principally through the portal vein, 

 only a small portion entering the lymphatics. In the blood the 

 peptone is converted into serum albumen, which is conveyed to 

 the capUlaries, through which it passes, bathing and nourishing 

 the tissues. The whole body is made up primarily of cells of 

 various forms, modified to meet each requirement. Nourished 

 by the serum albumen, the cells may divide again and again during 



