300 PHYSIOLOGICAL CHEMISTRY. 



in place of water ; the final result in this case is a product con- 

 taining a little more protein because of the content of albu- 

 min in the whey. 



Another important distinction, however, must not be lost 

 sight of. While the milk of the cow is sterile when it leaves 

 the udder it takes up from the hands of the milker or from 

 the air a large number of bacteria which speedily increase to 

 give a content of millions to the cubic centimeter. Most of 

 these are doubtless harmless and have no bad effect on the 

 milk ; of others this cannot be said, as their presence soon leads 

 to changes in the milk which may render it absolutely unfit 

 for vise as an infant food. Mother's milk is and remains ster- 

 ile and is therefore free from this danger. It must be re- 

 called further that the bactericidal behavior of human milk is 

 relatively very strong. While all milks seem to have a cer- 

 tain content of bacteriolysins, these anti bodies in mother's 

 milk are most potent as far as the destruction of the ordinary 

 bacteria is concerned. It is quite likely that no small portion 

 of the superiority of human milk as infant food is due to this 

 observed fact. 



All kinds of milk are affected to some extent by peculiar 

 flavoring or other accidental substances in the food of the 

 parent animal. It is a w r ell-kno\vn fact that cows having 

 access to certain weeds yield a milk with characteristic taste 

 and odor. In the same way many substances given as reme- 

 dies pass to some extent into the milk of the mother and may 

 have an effect on the nursing child. Bay rum used for bath- 

 ing the breasts of a nursing mother has been known to pass, 

 in part at least, into the milk and give to it a very strong odor 

 and taste. 



THE MILK OF OTHER ANIMALS. 



In some countries the milks of the goat and the ass have 

 economic importance, and mare's milk is used by certain Asi- 

 atic peoples in producing a fermented beverage. Analyses of 

 several kinds of milk are on record; some of these are given 



