232 



MILK AND ITS HYGIENIC RELATIONS 



upon the calcium and phosphorus content of both human and 

 cows' milk. The method employed by him was somewhat different 

 from the usual methods of previous observers. He used both 

 cows' milk and human milk, but in the former case the cream was 

 removed before the manipulations about to be described. In 

 human milk this was found not to be necessary. 



The milk was put through a Bechhold filter, working under 

 6 atmospheres' pressure of nitrogen. As a result of filtration 

 the colloids remain behind and the crystalloids come through. 

 Both varieties of milk were examined raw and after boiling for 

 five, ten, and thirty minutes. He found, as shown by the following 

 table, that greater loss occurred on boiling in human milk than 

 in cows' milk, more especially in the case of calcium. The de- 

 pression of the freezing-point, which was also investigated, showed 

 no appreciable change, as shown in the following table : 



The table shows that there is a greater loss in salt content, 

 owing to precipitation by boiling, with human milk than with 

 cows' milk. 



Using butter milk he obtained no difference between the raw 

 and the boiled filtrate, and he suggests that the acidity which has 

 developed in the butter milk has split off practically all the 

 phosphorus and calcium from the caseinogen. He also suggests 

 that this action probaby occurs normally in the stomach. 



It does not seem necessary to quote any further observations, 

 as it is generally admitted that there is a loss of calcium on heating 

 cows' milk, but in view of the higher percentage of this constituent 

 in cows' milk than in human milk, it is probable that there is still 

 an excess of calcium in cows' milk over human milk even after it 

 has been boiled. Moreover, if the milk is boiled and the precipitate 

 of calcium subsequently mixed up again in the milk, there need 

 not be any loss in the total lime content, although the calcium 

 may be present in a rather different form. When milk for infants 

 is prepared in a special vessel, as should always be the case, there 

 is no difficulty in obtaining the full calcium content in the milk 

 even after it has been boiled. 



