MILK. 297 



It is also possible to determine the total nitrogen by the Kjeldahl 

 method, and multiply this by the factor 6.25 to obtain corresponding total 

 protein. This gives a fairly good control. 



MILK PRESERVATIVES. 



Milk shippers and dealers often attempt to keep milk from spoiling 

 turning sour usually by the addition of some anti-ferment substance. 

 The propriety of such an addition has been much discussed. In general 

 the use of food preservatives cannot be too strongly condemned, as the 

 consumer has the right to insist on fresh, wholesome food, or food kept 

 sterile through previous heating. Boric acid, salicylic acid, formaldehyde, 

 sulphites and all similar bodies interfere more or less strongly with the 

 digestive functions when taken into the stomach. In the case of milk it 

 is sometimes a question of the lesser evil ; the trace of formaldehyde 

 required to effectually preserve it from acid fermentation is very small. 

 If no more than this minimum is used it is not likely that the harm from 

 using it would be very great, if at all noticeable. The use of such milk 

 is probably preferable to that of the sour, unpreserved milk often used by 

 children in the poorer quarters of our cities. 



MOTHER'S MILK. 



"We turn now to a short discussion of the chief points of 

 difference between mother's milk and cow's milk, which is a 

 subject of great practical importance. Success in substituting 

 cow's milk for mother's milk in the feeding- of small children 

 depends very largely on the extent and accuracy of our knowl- 

 edge here. It is a singular fact that we know much less about 

 the chemistry of human milk than we know of other milks, 

 and this is in part due to the difficulty in securing a perfectly 

 normal secretion for analysis. 



Because of the presence of certain salts milk has a so-called 

 amphoteric reaction, that is it shows an acid behavior with 

 blue litmus and an alkaline with red. In mother's milk the 

 alkaline reaction is stronger than in cow's milk, but the at- 

 tempts to determine it by titration with the usual indicators 

 lead to results of relatively little value because of the disturb- 

 ing action of the proteins present. The salts of mother's milk 

 are lower than in cow's milk. 



Analyses. The analysis of human milk seems to present 



