144 Dynamic Evolution 



The expenditure of energy through an 

 organ causes a concentration of energy in that 

 organ through which it is expended. In cows 

 we have such a concentration resulting from 

 the expenditure of energy in the production 

 of milk, and the amount of the concentration 

 is, within limits, proportional to the length 

 of time during which the expenditure is con- 

 tinued. Thus, a cow produces a greater 

 quantity of milk when she has her second 

 calf than when she had her first, more when 

 she has her third calf than when she had her 

 second, and so on up to her eighth or tenth 

 calf. The exact stopping point is uncertain 

 and probably varies with different cows. 



Early in the history of Holstein-Friesian 

 cattle in the United States there was estab- 

 lished an Advanced Registry for the record- 

 ing of those animals which had exceptional 

 merit in the production of large quantities 

 of butter fat. The standard for this was, of 

 course, made so high that only a compara- 

 tively small proportion of the whole stock 

 recorded in the herd books could get into the 



