MILK PRODUCTION 411 



difference in the amount and character of the milk from 

 two cows fed on precisely the same kind of food, the other 

 conditions being similar. These are determined by the 

 size and quality of the milk gland. But the relation be- 

 tween food and milk is very close, nevertheless. The milk 

 cells consist largely of protein. The fat also and probably 

 a part of the milk sugar is formed from albuminoids, hence 

 it is to be expected that their formation will be more or 

 less dependent on the protein in the food. This logical 

 expectation has been abundantly verified by experiments, 

 which have shown that the most abundant milk, yields have 

 been obtained from a fodder rich in protein. Before leav- 

 ing the subject, it may be said that, notwithstanding all 

 that is known about milk elaboration, many things about 

 it are not yet understood. 



The composition of milk. Milk is the opaque whitish 

 liquid secreted by the mammary glands of female animals, 

 and primarily designed for the nourishment of their young, 

 but in every age, it has also been made to furnish food 

 for the human family. In America about the only milk 

 used for man is that taken from the cow, but the milk of 

 sheep and goats and even of mares is also used thus in 

 various countries. Cow's milk is easily digested, and con- 

 tains in equilibrium all the constituents requisite for main- 

 taining life and promoting growth in bovines and also in 

 the human family, at least during the earlier periods of 

 development. Notwithstanding considerable and even wide 

 variations in the composition of milk from individual ani- 

 mals, the following may be given as approximately the aver- 

 age constituents of the milk of cows, sheep and mares 

 respectively : 



Digestive nutrients in 100 Ibs. 



ind of Dry matter in Carbo- Ether 



milk 100 pounds Protein hydrates Extract 



Ibs. Ibs. Ibs. Ibs. 



From cows 12.80 3.60 4.90 3.70 



From ewes 19.18 6.52 4.91 6.86 



From mares 9.22 1.99 5.67 1.21 



