CASEIN. 617 



are only necessary for the coagulation or the separation of the curd, 

 and the process of coagulation is hence a two-phase process. The first 

 phase is the transformation of the casein by the rennin, the second is 

 the visible coagulation caused by the lime-salts. This fact, which was 

 first proven by HAMMARSTEN, was later confirmed by ARTHUS and PAGES 

 and recently closely studied by FULD, SPIRO, and LAQUEUR and others. 1 



The curd formed on the coagulation of milk contains large quantities 

 of calcium phosphate. According to SOXHLET and SOLDNER, the soluble 

 lime-salts are of essential importance only in coagulation, while the 

 calcium phosphate is without importance. COURANT believes that the 

 calcium-casein on coagulation may carry down with it, if the solution 

 contains dicalcium phosphate, a part of this as tricalcium phosphate, 

 leaving mono-calcium phosphate in the solution. A solution of calcium 

 casein is not coagulated by rennin alone but only when soluble lime-salts 

 are added. Contrary to the generally accepted view that the soluble 

 lime-salts are of importance in the coagulation, VAN DAM 2 claims 

 that it is the quantity of lime combined with the casein which is of 

 importance in the coagulation process. The role of the lime-salts in 

 coagulation is not clear, and this follows from the chemical procedure 

 in rennin coagulation. *-*. *i 



If one makes use of a pure solution of casein and as pure rennin as 

 possible, then after coagulation it is always found that the filtrate con- 

 tains very small amounts of a protein, the whey protein, which is probably 

 formed in the coagulation. This behavior, which was first shown by 

 HAMMARSTEN, has been substantiated by many others and recently by 

 FULD, SPIRO and SCHMIDT-NIELSEN. Whey protein is generally con- 

 sidered as a proteose substance, and KOSTER 3 found 13.2 per cent nitro- 

 gen therein. In correspondence with these observations casein coagu- 

 lation with rennin is considered as a cleavage process, in which the chief 

 mass of the casein, sometimes more than 90 per cent, is split off as para- 

 casein, 4 a body closely related to casein, and in the presence of sufficient 



1 See Maly's Jahresber., 2 and 4; also Hammarsten, Zur Kenntniss des Kaseins und 

 der Wirkung des Labfermentes, Nova Acta Reg. Soc. Sclent. Upsala, 1877, Fest- 

 schrift; Zeitschr. f. physiol. Chem., 22; Arthus et Pages, Arch, de Physiol. (5), 2, 

 and Me"m. soc. biol., 43; Fuld, Hofmeister's Beitrage, 2, and Ergebnisse der Physiol., 

 1, Abt. 1, where a good review of the literature may be found; Spiro, Hofmeister's 

 3eitrage, 6 and 7, with Reichel, ibid., 7 and 8; Laqueur, ibid., 7. 



2 Zeitschr. f . physiol. Chem., 58. 



3 Hammarsten, 1. c.; Fuld, Bioch. Zeitschr., 4, and Hofmeister's Beitrage, 10; 

 Spiro, Hofmeister's Beitrage, 8; Schmidt-Nielsen, Hammarsten's Festschrift, 1906; 

 Koster, see Maly's Jahresber., 11, 14. 



4 It has been proposed to designate the ordinary casein as caseinogen and the curd 

 as casein. Although such a proposition is theoretically correct, it leads in practice 

 to confusion. On this accqunt the author calls the curd paracasein, according to 

 Schulze and Rose (Landwirthsch. Versuchsstat., 31). A summary of the literature on 



