228 MILK AND ITS HYGIENIC RELATIONS 



by heat unless the temperature be raised above that usually 

 employed for the milk of infants, but alterations apparently occur 

 in the molecule which affect the action of digestive ferments upon 

 this substance. The general trend of evidence shows that the 

 digestibility of caseinogen is increased by heating, but one or two 

 authors have believed the reverse. 1 



Netter (2) found that the digestion in the stomach of sterilised 

 cows' milk was almost as good as that of human milk, but he is 

 careful to point out that this does not imply that it is as good a 

 food in all other respects. 



Klemperer investigated in the laboratory the digestibility of 

 raw and boiled cows' milk, and was unable to detect any appreciable 

 difference between the two. 



Gerber investigated the effect of caseases derived from plants, 

 upon raw and boiled caseinogen. He found that these pancreatins 

 did not produce any amino-acids, whatever amount of ferment was 

 added. In heated milk, however, such action was obtained and 

 varied with the amount of the ferment added and with the tem- 

 perature to which the milk had been raised. No action occurred 

 under a temperature of 67 C., but heating for ten to fifteen minutes 

 at this temperature produced a small amount of soluble nitrogen. 

 From 75 C. to 85 C. there was considerable increase in the 

 amount of amino-acids formed, and very little further increase 

 was obtained when the milk was heated at 100 C. 



Brennemann worked on the clot formation of casein in the 

 stomach. He utilised for his investigations a young adult who 

 had the capacity of regurgitating food without experiencing any 

 discomfort. These experiments showed that the curd obtained 

 with raw milk was very tough and large, while with boiled or 

 sterilised milk it was soft and much finer in character. In con- 

 nection with the digestibility of caseinogen it may be remembered 

 that Brennemann and others found that the so-called ' casein curds ' 

 in infants' stools, occur only when raw milk is given.* This 

 suggests that caseinogen is more readily digested when the milk 

 has been heated. The increased ease in the digestibility of the 

 caseinogen of dried milk has already been referred to. 



It seems probable that the digestion of casein occurs for the 

 most part in the small intestine. This conclusion was reached 

 by Rotondi as a result of experiments on the digestion of both 

 cows' and human caseinogen. He showed that cows' and human 

 caseinogen were equally well digested by both pepsin and trypsin, 

 but that the pancreatic ferments attack caseinogen rather more 

 readily than fibrin, whereas the reverse occurred with the gastric 

 ferments, and he concluded that the chief digestion of caseinogen 

 probably occurred in the small intestine. 



The work of Bayliss and Plimmer in relation to the breaking 



1 Cp. de Jaeger, Hougardi, and others. * Cp. p. 36. 



