THE EXAMINATION OF MILK 427 



kept for half an hour at 70° C, and kept from subsequent 

 contamination, is free from these organisms. Macfadyen 

 and Hewlett {Trans. Brit. Institute Preven. Medicine (first 

 series) have, however, recently proved that heating in milk 

 for thirty seconds at 70° C. is sufficient to kill the following 

 pathogenic organisms : B. dipkttierice, B. typhosus, B. tuber- 

 culosis, Staph, pyogenes aureus. 



There are a number of objections to the use of sterilised 

 milk which do not apply to pasteurised milk. Undoubtedly 

 the chief disadvantage in the case of sterilised milk is that 

 the caseine is very much less digestible than in the case of 

 raw milk. In the case of children with weak digestions, 

 this may give rise to rickets, due in great part to the fact 

 that the children undergo a process of slow starvation, due 

 to an insufficiency of carbohydrates and fats. 



A second, though less important objection, is the fact 

 that the taste and smell of the milk are altered ; and 

 although this rarely matters in the case of young infants, it 

 sometimes causes difficulty with older children. Another 

 disadvantage is, that the greater part of the carbonic acid 

 gas in the milk is driven ofi^ thus inducing an alteration in 

 the composition of the phosphates, and a precipitation of 

 calcium and magnesium carbonates. Fourthly, some of the 

 fat globules coalesce, the result being that the emulsification 

 is not quite so perfect as in raw milk. Fifthly, the lact- 

 albumin is coagulated, and gives rise to the albuminous 

 skin which forms upon the surface as the milk cools, even 

 if it has not been boiled, and contains entangled in its 

 meshes a considerable quantity of fat, thus rendering the 

 milk correspondingly poor in this most important in- 

 gredient. 



The use of pasteurised milk is, however, strongly to be 

 recommended, particularly in the case of children, for the 

 following reasons : First, the digestibility of the casein is 



