404 CHEMISTRY OF THE PROTEIDS CHAP. 



In addition to caseinogen, lacto-globulm and the still hypothetical 

 lactalbumin, no other albumins are met with in milk. 1 Albumoses 

 are completely absent ; but milk contains a whole number of nitro- 

 genous extractives, such as Siegfried's phospho-carnic acid, or phospho- 

 sarctic acid, 2 provided that this substance be not formed from the 

 albumin during its manipulation. 



The Caseinogens of other Milks 



The caseinogen of human milk has been especially investigated by 

 Wroblewski, 3 Kobrak, 4 and Rohmann. 5 It is certainly different from 

 cow-caseinogen. Formerly great stress was laid on the point that 

 cow-caseinogen in curdling forms coarse flakes or a firm coagulum, 

 while human caseinogen gives rise to fine jelly-like flocculi, but 

 Courant 6 and Kobrak have proved that this difference depends simply 

 on the varying amounts of phosphorus found in the milk of the cow 

 and that of woman, and also on differences in the reactions of these 

 two milks. On the other hand, Kobrak 4 and Haffher 7 have found 

 that caseinogen is not precipitated directly by acids from human 

 milk, but only after the latter has been dialysed. According to 

 Kobrak, human milk possesses also quite a different acidity from 

 that found in cow's milk ; but after repeated precipitation and 

 re-solution human milk becomes more and more like cow's milk. 

 Kobrak explains this phenomenon as due to the admixture of a 

 second, alkaline albumin. The most important difference has been 

 discovered by Rohmann : human caseinogen gives a strong Molisch- 

 reaction, while cow-caseinogen gives a just perceptible reaction. 

 Therefore these two caseinogens must differ from one another. 



Donkey's milk has been studied by Ellenberger 8 and Storch. 9 In 

 its composition arid properties it closely resembles human milk ; the 

 caseinogen shows no peculiar features ; Storch succeeded in de- 

 composing the caseinogen into the same constituents as he obtained 

 with cow's milk. 



1 W. D. Halliburton, Journ. of Physiol. 11. 448 (1890). 



' 2 M. Siegfried, Zeitschr. f. physiol. Chem. 21. 360 (1895) ; Martin Miiller, ibid. 

 22. 561 (1897) ; K. Wittmaack, ibid. 22. 567 (1897) ; M. Siegfried, ibid. 22. 

 575 (1897) ; R. Kriiger, ibid. 28. 530 (1899). 



3 A. Wroblewski, Dissertation, Bern, 1894. 



4 E. Kobrak, Pfliiger's Archiv, 8O. 69 (1900). 



5 B. Rohmann, Verh. desfilnften intern. Physiol.- Kongresses zu Turin, 1901. 



6 G. Conrant, Pfluger's Arch. 50. 109 (1891). 



7 E. Haffner, Dissertation, Tubingen, 1901. 



8 Ellenberger, Arch.f. (Anat. u.) Physiol. 1899, p. 33 ; 1902, Suppl. p. 313. 



9 C. Storch, Monatsh.f. Chem. 23. 712 (1902). 



