418 ma:^ual of cattle-feeding. 



existence. Many eminent autliorities, however^ diRsent 

 from this view, and interpret the facts differently. The 

 point is still an undecided one, and it will therefore suffice 

 for our present purpose to have indicated the divergence 

 of views upon it 



Sources of the Ingredients of Milk. — The alhwnin- 

 oids of milk are obviously derived from the albuminoids 

 of the food or of the body. The albumin of milk seems 

 to be identical with that of the serum of the blood, but 

 the casein, as already noted, is not found in the body, but 

 is a product of the action of the cells of the milk-gland. 



The feet of the milk appears to be also formed from 

 albuminoids. This is shown both by microscopic examin- 

 ation and by other facts. By means of the microscope, 

 the formation of fat-globules in the epithelial cells of the 

 gland may be seen. Moreover, experiments have shown 

 that carnivorous animals, on a purely meat diet, pro- 

 duce normal milk, thus proving that milk-fat ^f/iai/ he 

 formed from albuminoids, and have also shown that the 

 greatest quantity of fat is generally produced on a ration 

 rich in protein. Experiments on herbivorous animals, to 

 which reference has already been made (pp. 174-170), 

 have shown no necessity for the assumption of a formation 

 of milk-fat from carbhydrates. 



The ojiilk-sugar may also be formed from protein or fat, 

 as the above-mentioned experiments on carnivorous ani- 

 mals show. In the case of herbivorous animals, however, 

 it is probable that a part of it at least is derived from the 

 carbhydrates of the food. 



