DIGESTION AND ASSIMILATION 93 



is sustained by the entire history of evolution in live stock. 

 At one time the Aberdeen poll was not the peerless beef 

 producer that it is today. There are also good reasons 

 for believing that centuries ago the Channel island breeds 

 gave milk less rich than the average of the milk obtained 

 from there now. Such modification finds further illustration 

 in the outcome from the way in which the heifer is grown 

 intended for the dairy, in the modifications made by corn 

 feeding in the bacon types of swine and in the improve- 

 ment of the milking qualities of the beef types of cattle. 



It has been noticed that when the female of a dairy 

 breed has been fed foods from calfhood onward that are 

 rich in elements of fat and muscle production, the tendency 

 in the system to produce flesh and fat is strengthened to a 

 degree that appreciably lessens the value of the same as a 

 producer of dairy products. Because of this, the most suc- 

 cessful growers of dairy stock are careful to rear females 

 intended for the dairy on foods that make growth of frame 

 and muscle rather than fatty tissue. It will be observed 

 that this tendency in food appropriation in the system is 

 brought about by the influence of food only. 



The same is true of modification in the character of 

 bacon grown almost entirely on corn. In one generation 

 it will so modify the bacon produced that it will not be 

 assigned first place in the market, although it would have 

 been assigned first rank had it been properly grown. Let 

 such feeding be continued for a few generations and the 

 bacon form will be greatly modified. It will bear a much 

 closer resemblance to the form of the lard breeds. 



The milk production of any class of beef cattle may 

 also be modified through food fed so as to considerably 

 increase the milk flow. It is a fact the beef breeds are not 

 equal in milk production, though fed similarly, a result 

 owing doubtless in part to inheritance, and in part to nutri- 

 ents contained in the foods which furnished the major 



