72 A STUDY OF FARM ANIMALS 



The remarkable thing about the vitamines is, that they 

 have never been actually separated out and isolated by them- 

 selves for study. Yet already a large amount of experi- 

 mental feeding of human beings has clearly shown their 

 existence and the important part they play in nutrition. 

 Without question the vitamines influence the nutrition of 

 farm animals. This fact has been brought out in feeding 

 experiments on swine, notably by Prof. Evvard, of Iowa. In 

 fact, we may assume that the vitamines in milk, green 

 forage, and vegetables account in part for the great value 

 credited to these substances by feeders of animals. 



Comparing plants and animals, we see that the plant 

 obtains its food from the air and from the mineral matter in 

 the soil, from which it develops a form made up of cells that 

 are largely carbohydrates. The farm animal obtains its 

 nutriment from the plant, from which is created a form, 

 also composed of cells, but, in this case, of nitrogenous mate- 

 rial. During the day the plant sucks in carbon dioxide from 

 the air through its leaves, and holds the carbon, and gives 

 off the oxygen. The animal, on the contrary, draws the air 

 into the lungs, uses the oxygen from it, and then breathes 

 out carbon dioxide. Thus we see that these two great 

 groups of living matter, the plants and animals, are of vital 

 importance to each other, and have much in common. 

 Without the plant or its products the animal under ordinary 

 conditions could not live; while by feeding on it the beast 

 converts the vegetable substance into a yet more concen- 

 trated and more valuable food material for men. 



A part of this vegetable substance, however, is not taken 

 up by the animal body; but, following a softening and re- 

 ducing process, is excreted as manure. This excretion, 

 placed in contact with the roots of the plant, furnishes 

 nutriment and stimulates increased production. Thus the 

 plant furnishes nourishment to both the animal and vege- 

 table kingdom. 



