212 AGRICULTURE FOR BEGINNERS 



In the fourth place, we feed to produce strength for work. 

 An animal poorly fed cannot do so much work at the plow 

 or on the road as one receiving all the food needed. 



Both food and the force produced by it result from the 

 activity of plants. By means of sunlight and moisture, 

 a sprouting seed, taking out of the air and soil different 

 elements, grows into a plant. Then, just as the plant feeds 

 upon the air and soil to get its growth, so the animal feeds 

 upon the plant to get its growth. Hence, since our animals 

 feed upon plants, we must find out what is in plants to 

 know what animal food consists of. What, we are now 

 ready to ask, are plants made of ? 



Chemists have found out that in studying plants there 

 are five important groups of substances to be considered. 

 These are protein, carbohydrates, fat, mineral matter, and 

 water. What is each of these, and what use does the 

 animal make of each ? 



First, protein, the most important, must be considered. 

 The animal food called by this queer name is not unknown 

 to you. You have all your lives seen it in compounds like 

 the white of an egg, lean meat, or the gluten of wheat. It 

 is made of three gases (oxygen, hydrogen, and nitrogen) 

 and two solid bodies (carbon and sulphur). The bodies 

 of plants do not contain very much protein. Roots, grass, 

 hay, and straw have a very small amount of it. On the other 

 hand, all plant seeds contain a good deal of this substance. 

 What use do the animals make of protein ? Animals form 

 their new blood, their muscles, and their lean meat from 

 protein food. It is easy, then, to see the value of protein. 



In addition, this substance rebuilds largely the waste 

 of the body. This is harder to understand. Every boy, 



