ALBUMEN AND STARCH. 83 



Albumen and Gluten contain nitrogen; and 

 this nitrogen renews the blood and builds up the 

 lean muscular part of the body. Besides, albu- 

 men and gluten enter into the composition of 

 the bones. 



Starch and Gum contain no nitrogen, but are 

 rich in carbon. This carbon is required to 

 produce and keep up the animal heat of the 

 body. Men and animals when healthy and 

 taking plenty of exercise, by which their respira- 

 tion is quickened, and especially in cold weather, 

 require large amounts of carbon, which uniting 

 with the oxygen of the atmosphere forms carbonic 

 acid. This chemical union is, strictly speaking, 

 a combustion of the carbon, similar to that of a 

 slow fire, and produces the animal heat of the 

 body. The chemical composition of starch, gum, 

 and sugar are analogous. The fat of animals, if 

 pure, contains no nitrogen, but it is composed of 

 carbon, hydrogen, and oxygen. Should an animal 

 be debarred from exercise and fed upon a sub- 

 stance rich in carbon, as indian corn or rice, it 

 would rapidly increase in fat. Carnivorous ani- 

 mals are nearly destitute of fat, while domestic 

 stall-fed animals acquire a large amount of it. 

 If the fattened animal is allowed exercise, or set 

 to work, the fat quickly disappears. 



Dogs and cats, .when fed on a mixed diet, 

 accumulate fat; so that by feeding them with 



