20 



THE FEEDING OF ANIMALS 



element. Iron is taken up by plants and animals in small 

 quantities only, but is absolutely essential to their growth 

 and welfare because of its important relation to certain 

 metabolic processes. (See Par. 200.) 



PKOPOKTIONS OF THE ELEMENTS IN PLANTS AND 

 ANIMALS 



In order to reach an intelligent understanding of the 

 relation of supply and demand which exists between the 

 vegetable and animal kingdoms and the raw materials 

 of the inorganic world, it is necessary to know the propor- 

 tions in which the elements are foimd in living organisms. 



24. Elements in plants. — ^It has been estimated by a 

 German scientist, Knop, that if all the species of the 

 vegetable kingdom, exclusive of the fungi, were fused into 

 one mass, the ultimate composition of the dry matter of 

 this mixture would be the following: 



Per cent 



Carbon 45 



Oxygen .... . . .... .42 



Hydrogen . . . . 6.5 



Nitrogen 



Mineral compounds (ash) 



1.5 

 5 



The composition of various single species or parts of 

 a plant, such as the fruit or straw, shows considerable 

 variation from these average figures: 



Table I 



