MAKING PLANS THAT WORK 65 



mercial fertilizer merely to maintain the status 

 quo. If the hay is fed to a cow, and her manure re- 

 turned to the hay field the value of the boughten 

 fertilizer then needed will drop to fifteen per cent 

 or less of the sale value of the hay. This per- 

 centage can be further reduced if the hay is not 

 fed exclusively to cows, if, in other words, we pay 

 proper respect to the biological farm-balance. 



Darwin first described the phenomenon of bio- 

 logical balance. He showed that if there were no 

 house cats in England there would be no clover 

 hay: house cats destroy field mice which, if not 

 thus held in check, would destroy the earth worms 

 that in their turn or rather, turning, for it is their 

 turning over of tons of soil per acre keep the 

 clover flourishing. House cats have been domesti- 

 cated in England since before written history, so 

 they have muscled in on the biological balance. 

 As yet they have no place in the American country- 

 side. As long as there are birds to eat no cat will 

 bother with field mice. Those who write our game 

 laws, at long last realizing this, have finally turned 

 on the cats. Even our farmers are beginning to 

 see though still as through a glass, darkly that 

 the birds are our main line of defense against the 

 insects, which, but for an accident of temperature, 

 would long since have extinguished mankind. Yet 

 few farmers appreciate the importance of biolog- 

 ical balance in the conduct of their own business. 



