RELATION OF ANIMALS TO MAN 31 
economically possible. (4) In the production of these 
finer products much of the cssential materials of plant 
growth are left on the farm; this means land improve- 
ment. (5) The rearing of live stock makes it possible 
to arrange a better rotation of crops; and this practice 
helps to maintain the fertility of the soil. (6) Labor is 
ADAPTING POWER TO WORK REQUIREMENTS 
European countries have learned to adapt their power to the kind of work to be 
performed. They do not use a ten-horsepower boiler and engine to perform the 
work which can be done by a half horsepower. 
better utilized also, thus securing greater prosperity to 
the community and a higher skill of those operating the 
farms. 
13. Disadvantages of keeping live stock.—More capital 
is required to operate a given area of land where animals 
are kept than on exclusive grain or other crop farms. 
This investment is in animals, buildings, feed and labor. 
The perishable nature entails also a great risk in the in- 
vestment. Not only the products of a single year, but 
the growth of a number of years, may be suddenly swept 
away by disease. Then, when an animal has been prop- 
