20 FEEDING ANIMALS. 



slum, silicon, and iron. These are the principal elements. 

 Sometimes iodine, bromine, and a few other simple element- 

 ary bodies are found in plants and animals. Vegetable and 

 animal substances are often looked upon as very different 

 in their composition, but the most important of these 

 elements are quite identical in vegetables and animals. 

 Vegetable albumen, which is often found coagulated in 

 boiling vegetable juices, is identical with the albumen of 

 the white of eggs. The fibrin of blood is in no wise differ- 

 ent from the fibrin of wheat and many other cereal grains; 

 and the curd or casein of milk is the same as the legumen 

 of peas and beans. And these substances are all converti- 

 ble into each other within the animal organism. We shall 

 consider the seuarate elements of vegetable foods in the 

 next chapter. 



It was formerly supposed that animals had the power of 

 changing and combining the elements of their food into 

 such form as their necessities required ; but it is now 

 believed that they do not possess the power of even com- 

 pounding the substance of the muscles from its elements, 

 and can only appropriate from vegetables what they find 

 ready formed for their use that the vegetable must elabo- 

 rate, and the animal can merely appropriate. Food, then, 

 must contain all the elements of animal bodies. It will 

 therefore be profitable to consider the composition of animal 

 bodies the blood, the flesh, or muscles, the fat, the bones, 

 the skin, hair or wool, horn, etc. 



1st. The blood, on an average, contains water, 79 per 

 cent., and 20 per cent, of organic matters, consisting prin- 

 cipally of a nitrogenous substance analagous to fibrin, 

 which separates in long strings when blood is beaten with 

 a stick immediately after being drawn, and some albumen, 

 which remains dissolved in the liquid part of the blood or 

 serum. On heating, the albumen coagulates and separates 

 into whitish flakes, like the white of eggs, with which it is 



