MAMMARY GLANDS 



41 



of casein and calcium. As it is often necessary in infant feeding 

 to replace the mother's by cow's milk, it is important to con- 

 sider some of the differences between various milks. The 

 following table is modified from Konig: 



Woman 



Cow . 



Colostrum of cow 



Goat 



Sheep 



Mare 



Ass . 



Hog . 



The composition of human milk varies with the constitution, 

 with the state of nutrition, with age, with the complexion, 

 at different stages of lactation, from the two breasts, etc. It 

 is distinguished from cow's milk mainly by the low percentage 

 of protein and the high percentage of sugar. The difference 

 in the protein causes human milk to form a more flocculent 

 and more easily digested precipitate when coagulated. Practi- 

 cally all the phosphorus is in organic combination as nucleon 

 and caseinogen, and is not, as in cow's milk, found as pseudo- 

 nuclein. The casein in woman's milk is more difficult to pre- 

 cipitate by acids, salts, and rennet, and is also more easily 

 redissolved by an excess of acid. 



Human milk contains the fatty acids oleic, stearic, palmitic, 

 butyric, caproic, capric, and myristic, combined with glycerin. 

 Cow's milk contains, in addition, caprylic and arachic acids. 

 Human milk is poor in volatile acids. The chief base is potas- 

 sium, while that of other animals is calcium. 



The cells of the mammary glands, which during pregnancy 

 become active for the first time, undergo histological changes 

 of such a nature that each cell increases in size, undergoes a 

 fatty metamorphosis, the nuclei divide, and then a portion, 

 at least, of the cell, if not the whole of it, disintegrates. The 

 fragments form the constituents of the milk. There are known 

 instances where the secretion of milk has been suppressed by 



