3o8 SCIENTIFIC FEEDING OF ANIMALS 



grow again, or whether they remain intact, has not 

 been proved. 



Milk is therefore a product of the mammary gland, 

 and it is upon the development and productiveness 

 of this organ that the extent to which the quantity 

 and composition of the milk can be influenced by 

 other factors — particularly the food — depends. 



(2) The influence of the constitution of the animal 

 upon the formation of milk. 



(a) Breed and individuality. 



The development of the mammary gland, like 

 any other organ, cannot be increased separately by 

 any kind of feeding, but is to a certain extent heredi- 

 tarily fixed. Therefore it arises that between the 

 several breeds and individuals considerable differ- 

 ences in the quantity and composition of the milk 

 are to be found. The natural breeds of cattle not 

 bred for the production of milk only give some 

 400-500 litres (88-110 gals.) of milk per annum, in 

 which, though, the percentage of solid substances is 

 high. The cultivated breeds have, however, been 

 gradually raised to an extraordinarily high pitch 

 as milk producers. Cows which annually give more 

 than 5000 litres (1100 gals.) milk with more than 

 3 % of fat are nowadays not rare. Definite informa- 

 tion regarding the milk yields of the various breeds 

 is not easy to give, on account of the variety of con- 



