ix THE PHOSPHO-GLOBULINS 399 



Soldner 1 distinguishes two series of salts, while Courant 2 describes 

 three series. 



"Eucasein" is ammonium caseinogenate, 3 , while "nutrose" and 

 " plasmon " 4 are the sodium caseinogenates. 



In addition to being precipitated by chemical agencies, calcium 

 caseinogenate, or the caseinogen + calcium phosphate compound 

 occurring normally in milk, is also precipitated by relatively feeble 

 physical factors as alluded to above. According to Hermann 5 calcium 

 caseinogenate is .precipitated if one add to its solution large amounts 

 of calcined clay or animal charcoal. According to Salkowski 6 the 

 caseinogeri-lime compound is precipitated on letting milk stand with 

 chloroform. Zahn 7 states that the lime salt is precipitated whenever 

 it comes into contact with porous clay, and therefore if milk be sucked 

 through a Chamberland filter the caseinogen remains behind, while 

 the other albumins pass into the filtrate. 8 Sodium caseinogenate, on the 

 other hand, is filtrable. On this property of caseinogen, namely, to be 

 precipitated by clay, Hempel 9 has based a method of estimating its 

 molecular weight, but according to Simon 10 this is not permissible. 



In milk, caseinogen is present as calcium caseinogenate, and, 

 according to Courant, 2 not as a neutral salt, but as calcium di- 

 caseinogenate and in combination with calcium phosphate. How this 

 latter is brought about is as yet unknown. The calcium caseinogenate, 

 as such, may possess the power of keeping somehow the neutral 

 calcium phosphate, which is also present in milk, in solution or in a 

 finely subdivided state, or there may be formed in the milk a true 

 double salt of calcium caseinogenate and calcium phosphate, as is 

 believed by Lehmann and Hempel. 11 At any rate, when caseinogen is 

 precipitated calcium phosphate is thrown down simultaneously, and so 

 is the whole of the fat, the emulsion of which is also due to the 

 presence of calcium caseinogenate. For this reason it is extremely 

 difficult to purify caseinogen from fat and from calcium phosphate. 12 



1 F. Soldner, Dissertation, Erlangen, 1888. 



2 G. Courant, Pfl'Ager's Arch. 5O. 109 (1891). 



3 E. Salkowski, Zeitschr. f. Biol. 37. 401 (1899). 



4 W. Praussnitz and H. Poda, ibid. 39. 277 (1900). 



5 L. Hermann, Pfliiger's Arch. 26. 442 (1881). 



6 E. Salkowski, Zeitschr. /. physiol. Chem. 31. 329 (1900). 



7 W. Zahn, PJtilger's Archiv, 2. 598 (1870). 



8 D. F. Harris, Journ. of Physiol. 25. 207 (1900). 



9 W. Hempel, Pfliigers Archiv, 56. 558 (1894). 



10 G. Simon, Zeitschr. f. physiol. Chem. 33. 466 (1901). 



11 W. Hempel, "J. Lehmann's Milehuntersiichungen, " PJtilger's Archiv f. d. ges. 

 Physiol. 56. 558 (1894). 



12 R. Cohn, Zeitschr. f. physiol. Chem. 22. 156 (1896) ; W. Hempel, " J. Lehmann's 

 Milchuntersuchungen, " Pflilger's Archiv f. d. ges. Physiol. 56. 558 (1894). 



