CASEINOGEN 15 



paracasein was independent of the calcium salts present and 

 this has been confirmed by later observers. Some chemists 

 (Loevenhart^^ and Briot^''), have claimed that an essential part 

 of the rennin reaction is a modification of the mineral con- 

 stituents, but Harden and Macallum^^ have recently shown that 

 if caseinogen solutions are treated with sufficient rennin 

 (1 : 1000) no addition of calcium salts is required: Schryver^ 

 found that clot formation could be obtained in the entire absence 

 of calcium ions. Duclaux ^^ was the first to find that no proteo- 

 clastic cleavage is produced by the action of rennin and this has 

 been confirmed by Van Slyke and Bosworth,2o Geake,^^ and 

 Harden and Macallum.^^ Loevenhart ^^ suggested that caseino- 

 gen and paracasein were chemically identical and that the differ- 

 ences in behaviour were due to changes in molecular association 

 or aggregation. This view is supported by Van Slyke and Hart^^ 

 and Van Slyke and Bosworth (vide supra) who suggested that 

 calcium caseinogenate is split by the action of rennin into two 

 molecules of calcium paracaseinate which is identical in per- 

 centage composition with the' original substance. Liwschiz^^ 

 attempted to differentiate caseinogen and paracasein by biolog- 

 ical methods. Three methods were tried, precipitation, com- 

 plement binding, and anaphylaxis, and of these only comple- 

 ment binding gave positive results under certain conditions. 

 The other two methods entirely failed to distinguish between 

 the two substances. Schryver^ has suggested that all the 

 substances necessary for clot formation pre-exist in milk and 

 that aggregation is prevented by the absorption of simpler 

 molecules from the system. He formed the conception that a 

 ferment, for which the colloidal substances could act as a sub- 

 strate, could clear the surface of such substances of adsorbed 

 bodies and thus allow aggregation (clot) formation to take 

 place. He found that milk serum, Witte's peptone, or glycine, 

 inhibited clot formation by rennm, and also that apparently 

 typical milk clots could be formed by the addition of calcium 

 chloride to calcium caseinogenate solutions and warming. 

 These differ from rennin clots, however, in their ability to pro- 



