THE ORGANIC CONSTITUENTS OF MILK 39 



are separate bodies. Bauer (i) believes that the partial dis- 

 crepancies in Hamburger's work can be attributed to the method 

 employed. 



Hamburger's work was confirmed by Schlossmann and Moro, 

 who showed, by means of the precipitin reaction, that the proteins 

 of cows' milk must be regarded as ' foreign ' to those of the human 

 species, and that the caseinogen and lact-albumin in the milk of each 

 species are distinct bodies. They found, further, that lact-albumin 

 was biologically identical with the albumin of the blood. Small 

 amounts of lacto-globulin were obtained from cows' milk, but 

 Schlossmann (i) considers that from the nutritional standpoint this 

 body may be safely neglected. The amount is very small, and it 

 resembles albumin so closely as not to require separate con- 

 sideration for infant feeding. Schlossmann (i, 2) considers that 

 as the albumins of blood and of milk are identical substances, 

 the albumin in milk can readily be, and probably is, absorbed 

 directly by the infant in the early days of life. 1 



A few years later (1908) Bauer (2) showed that much finer differ- 

 entiation of proteins could be obtained by using the method of 

 ' complement deviation.' This method has been mainly used by 

 him in his subsequent extensive investigations in this direction. 



The work of Bauer (5) and of his pupil Kollmeyer shows that 

 caseinogen must be placed biologically in a class by itself. 



The differentiation between the caseinogen and the whey- 

 protein of the same species was more marked than that between 

 the caseinogen of the cow and of the goat. On the other hand, 

 lact-albumin anti-sera, both of cows' milk and of human milk, reacted 

 with the serum-protein of the corresponding species, and seemed 

 to show the biological identity of the whey- and serum-proteins. 



Using this method, which is more sensitive than the precipitin 

 method, Bauer (2) and (3) obtained no reaction between a lacto- 

 serum obtained by the injection of cows' milk, and ox-serum. He 

 attributes this to the large amount of casein present, which body 

 does not react with blood-serum. 



Bauereisen, using the precipitin method, showed the biological 

 identity between the whey-protein and the proteins of the blood, 

 and placed caseinogen somewhat apart from these in its biological 

 properties. He considers that the whey-proteins of colostrum can 

 be absorbed directly by the infant and form part of the blood 

 protein. 



Bauer and Engel (1911) undertook further comprehensive 

 investigations into the relationship of the milk-proteins, using the 

 method of complement deviation. 



The caseinogen was separated out first by the acetic acid method 

 of Engel (i). This was filtered off and the filtrate subjected to half 

 saturation with ammonium sulphate. This treatment precipitated 



1 Cp. Chap. VI: 



