Process of Power Changes 17 



Maid had developed more trotting power than 

 ever existed in any ancestor, because, at the time 

 she was conceived, no horse in the world had suc- 

 ceeded in trotting a mile in 2:24y 2 , and those 

 which had approached that speed were not in her 

 ancestry. Yet after her trotting development un- 

 der trotting exercise had passed the point of any 

 possible inheritance, she made further gains for 

 seven years under continued training. At seven- 

 teen years of age she broke the world's record 

 four times in succession. 



During the past century, thousands of horses 

 have developed more trotting power than was 

 called for by their inheritance because their de- 

 velopment under continued exercise exceeded 

 anything which ever existed in any ancestor. 

 And on the race tracks of the United States 

 during 1917, more than one hundred trotters 

 over ten years of age showed more speed than 

 they ever showed before. 



There is another example of continued develop- 

 ment of powers under continued exercise, and 

 that is that of milk-production by cows. A cow 

 produces a certain amount of milk per day when 

 she has her first calf, a larger amount when she 



