18 The Feeding of Animals 



As a result of these conditions which relate to the 

 supply of useful nitrogen and to its important role, we 

 find that it has assumed a prominent place in com- 

 merce. It is the most costly ingredient of fertilizers, 

 and the value of commercial cattle foods is sometimes 

 based almost wholly upon their content of this element. 

 For these reasons, the control, even though only par- 

 tial, which the farmer may now assume over the in- 

 come and outgo of the nitrogen compounds valuable 

 to agriculture is a triumph of modern science, and an 

 important feature of rural economy. 



Sulfur is a common and familiar substance. As an 

 element it is not widely distributed in nature, but its 

 compounds are found in all soils and natural waters, 

 and in all the higher forms of animal and vegetable life. 

 We know it as "brimstone" when fused in sticks and 

 as "flowers of sulfur" when in a finely divided form. 

 Its most common commercial compounds are sulfuric 

 acid and the sulfates of potash, soda, lime and mag- 

 nesia. This element is an essential part of some of 

 the most important tissues of the animal body, and is 

 supplied in food in the form of the sulfates and in its 

 proteid combinations. 



PhospJwrus occupies an important place among the 

 elements of nutrition. In the uncombined form it does 

 not exist in nature, as that found in laboratories is 

 produced only by chemical means. Its compounds are 

 found everywhere. The phosphates of calcium, mag- 

 nesium and iron are widely distributed in soils and 

 large deposits of calcium phosphate are known, from 

 which is obtained the crude phosphatic rock that serves 



