340 THE FEEDING OF ANIMALS 



sustain a permanent, though not extensive, modification. 

 The weight of testimony bears out the statement that 

 the content of solids in milk cannot be modified at will 

 by the farmer, but is largely determined by causes not 

 under his control, such as breed and individuality, 

 although feeding and treatment, especially the latter, 

 have more or less influence upon the character of the 

 milk secreted. It is possible, even probable, that continu- 

 ous feeding, either very poorly or very highly, may bring 

 about in time a permanent change in a cow's milk, but 

 today no one is wise enough to point out a way of defin- 

 itely controlling this product through the food. 



441. Effect of food upon the constitution of milk 

 solids. In the discussions relative to feeding dairy cows, 

 another point has received much attention, viz., the 

 effect of foods upon the proportions of the constitu- 

 ents which make up the dry matter of milk. A popular 

 notion has prevailed that it is possible to "feed fat into 

 milk," having its origin in part, perhaps, in miscon- 

 ceptions as to the manner of milk formation. If the 

 mammary gland served simply to capture the unchanged 

 constituents of the food, then it might be reasonable to 

 expect the milk to partake of the character of the digested 

 nutrients and be "fat" or "lean" according to the pro- 

 portions of proteins and fats supplied to the animal. 

 When, however, we consider that this gland has the func- 

 tion of transforming the raw material of the food into a 

 milk which is characteristic of the breed or of the individual 

 in accordance with somewhat fixed constitutional limi- 

 tations, and that from the same food the Jersey cow will 

 make Jersey milk and the Holstein cow Holstein milk, 

 that a cow which starts in life giving thin milk is never 

 transformed into a producer of rich milk, we can easily 



