CHAPTER III 



THE CHEMICAL ELEMENTS OF ANIMAL NUTRITION 



THE facts which are fundamentally necessary to a 

 broad understanding of tne economy of cattle feeding, 

 pertain, first of all, to the materials out of which vege- 

 table and animal tissues are constructed. It is impor- 

 tant to know both what these are and what are their 

 sources. 



About seventy substances are now believed to be 

 chemical elements, i. e., substances that cannot be re- 

 solved into two or more simpler ones, and of which, so 

 far as known, all forms of matter are composed, the 

 variety of combinations being almost infinite. It is 

 remarkable that comparatively few of these fundamental 

 substances, about one -fifth, are intimately related to 

 the growth of plants; and those that occupy a promi- 

 nent place in animal nutrition are even less in number. 



It is necessary to mention only fifteen elements in 

 this connection, some of which are of minor impor- 

 tance: carbon, oxygen, hydrogen, nitrogen, sulfur, 

 phosphorus, chlorine, silicon, fluorine, potassium, so- 

 dium, calcium, magnesium, iron and manganese. 



At ordinary temperatures, four of these, oxygen, 

 hydrogen, nitrogen and chlorine, are gases, and the re- 

 maining ones are solids. Four are constant and im- 



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