FOOD, WORK, AND GROWTH OF ANIMALS 189 



Kittle half-grown "runt" of a horse may eat nearly as 



much as a fine powerful draft horse, and yet not be 

 Me to do half the work. It is, therefore, just about 

 a- expensive to keep. The poorer the class of 

 stock the more expensive it is to keep. 



Questions 



1. The food of most animals consists of what? 2. How 

 do the foods of animals differ from the foods of plants? 

 3. How are the raw materials of the earth and air con- 

 verted into animal foods? 4. Do living animals ever cease 

 to grow? 5. What changes are constantly going on in the 

 bodies of animals? 6. To effect the changes in animal 

 bodies what is necessary? 7. What is necessary to keep 

 up the temperature of animal bodies? 8. What three things 

 are necessary to enable an animal to work? 9. Why is it 

 more expensive to keep scrub stock than it is to keep more 

 valuable animals? 



PROBLEM 



Let us suppose that we have to feed two milch cows, A 

 and B. They both eat about the same amount of food and 

 cost the same to keep. A, however, gives an average of 

 3 gallons of milk a day, while B gives only an average of 

 7 quarts.. Milk is worth 20 cents a gallon. What is the ap- 

 proximate value of the milk produced in a month of 30 days 

 by each cow? 



