ix THE PHOSPHO-GLOBULINS 401 



according to Osborne as stated on p. 274, while the haptogen- 

 membrane has been studied by Jamison and Hertz, see p. 276. 



Casein 



Milk when acted upon by rennet is coagulated owing to the 

 rennet-ferment converting caseinogen into casein, *or, to use the 

 terminology of Hammarsten 1 changing 'Kasein' into ,'Parakasein.' 

 Casein resembles the unaltered caseinogen in being readily soluble in 

 alkalies, but its lime salt is insoluble. If, therefore, a soluble lime salt 

 is present in solution along with caseinogen, then under the influence 

 of rennet-ferment the soluble calcium caseinogenate is changed into 

 the insoluble calcium caseinate and the milk curdles. 2 



The process of coagulation takes place in two stages, and these 

 may be separated from one another temporarily. 3 The first stage 

 consists in the fermentative change whereby caseinogen is converted 

 into casein, and depends solely on the presence of the rennet- 

 ferment ; the second stage is characterised by the curdling of the 

 milk or caseinogen-solution containing the altered casein. This 

 curdling can only take place, however, in the presence of lime 

 salts ; for if the lime salts of the milk be removed by an oxalate, 

 then the casein does not separate out. 4 Halliburton 2 reserves the 

 expression casein for the coagulated caseinogen, and uses the term 

 caseinogen for the native albumin, so as to express the analogy 

 which exists between the coagulation of the mother-substance of 

 casein and the mother-substances of fibrin and myosin, which he 

 terms fibrinogen and myosinogen. 



In all its other properties casein completely agrees with caseinogen 

 except that it is more readily precipitated by sodium chloride, and 

 therefore casein may undergo a kind of coagulation 5 if large amounts 

 of sodium chloride be present. Want of knowledge of this fact 

 seems to have led to many of the contradictory statements found in 

 the literature. 



The process of true coagulation is according to Hammarsten 1 an 



1 0. Hammarsten, Maly's Jahresber. f. Tierchemie, 2. 118 (1872) ; Sitzungsber. der 

 Konigl. GesellscJwft d. Wissenschaften zu Upsala, 1877. 



2 W. D. Halliburton, Journ. of Physiol. 11. 448 (1890) ; 0. Hammarsten, Malys 

 Jahresber. f. Tierchemie, 2- 118 (1872) ; Sitzungsber. der Konigl, GesellscJiaft d. 

 Wissenschaften zu Upsala, 1877. 



3 S. Ringer, ibid. 12. 164 (1891). 



4 M. Arthus, Arch, de Physiol. norm, et pathol. 1893, p. 673 ; 1894, p. 257 ; S. 

 Ringer, ibid. 12. 164 (1891) ; O. Hammarsten, Male's Jahresber. f. Tierchemie, 2. 118 

 (1872) ; Sitzungsber. der Konigl. Gesellschaft d. Wissenschaften zu Upsala, 1877. 



5 0. Hammarsten, Zeitschr. f. physiol. Chem. 22. 103 (1896). 



2 D 



