6 MANUAL OF MILK PRODUCTS 



The transudation theory fails to take account of the fact 

 that the fats in the milk are unlike the fats in the food or body, 

 and that casein and milk-sugar are not found in the blood or 

 the mammary gland itself. 



In discussing this theory, Armsby says, "The milk is not 

 simply secreted from the blood like the urine in the kidneys, 

 or the digestive juices in the stomach and intestines, but is 

 formed in the milk glands from the cells of the gland itself — 

 it is the liquefied organ. This is shown even by the composition 

 of its ash, which, like that of all tissues, contains much potash 

 and phosphate of lime, while the fluids of the animal body are 

 poor in these substances and rich in chloride of sodium (com- 

 mon salt) ; the ash of milk contains three to five times as much 

 potash as soda, while the ash of blood, on the other hand, con- 

 tains three to five times as much soda as potash. Were the milk 

 simply a transudate from the blood, it would have a similar 

 composition, and could not serve as the exclusive food of the 

 young animal, since it would not contain all the elements 

 necessary for growth; but, since it is a liquefied organ, it is 

 exactly adapted to. build up other organs." 



"Another theory that has had many supporters is that milk 

 is the result of the separating of part of its constituents, as the 

 water serum and salt from the blood, and part due to a fatty 

 degeneration of the cells lining the alveolar cavities, the fat 

 globules being due to the degenerated cells and the casein due 

 to the undegenerated portion of the cells. This theory is 

 actively supported by many of the best physiologists. Smith, 

 after examining all the phases of milk secretion, sums up the 

 whole as follows : ' The process of milk secretion may there- 

 fore be regarded as a process of metabolism of the epithelial 

 cells, which undergo decomposition and discharge the resulting 

 products into the excretory ducts/ He regards 'fat as a prod- 

 uct of fatty degeneration of the protoplasmic cell contents, 

 for it is not increased, but actually diminished, by an increase 



