355 
composition of this compound agrees reasonably well with the 
formula 
Cag (P04)2 Ca. caseinogen. 
According to Courant (IT) a solution can be obtained showing 
essentially the same alkalinity to lacmoid and the same acidity to 
phenolphthalein and conducting itself to rennin in the same manner, 
as fresh milk, by bringing together lime water, caseinogen, and 
phosphoric acid in the quantities indicated in the following equation : 
/OH /OH 
6 Ca(OH)2+2 Cas— OH+ 4 H3P04=Ca3(P04)2+2 Cas— 0\^ , 
\OH \C)/^^+ 
Ca (H2P04)/12 H2O. 
In other words, the mixture or compound 
/OH 
[Ca3(P04)/2 Cas-0^.. +Ca(H2P04) J 
\0>^a 
closely approximates the condition of the caseinogen and phosphates 
as these substances exist in fresh milk. AYliether these several 
substances are merely intimately mixed together or whether they 
form some loose chemical combination similar to a complex double 
salt can not be definitely determined at present. According to 
Courant, how^ever, all of these substances are necessary to the rennin 
coagulation, namely, dicalcium caseinogenate, soluble calcium salts, 
represented in the equation by monocalcium phosphate, and also 
tricalcium phosphate. According to this author only the dicalcium 
caseinogenate is altered in the rennin coagulation of niilk, this being 
converted into paracasein. According to him the role of the soluble 
salts of the alkaline earths (calcium) in this process is simply to 
diminish the solubility both of the caseinogen itself and the para- 
casein. This last notion is in harmony with certain observations by 
Ringer (18), who found that even fresh milk is coagulated by warm- 
ing with small amounts of calcium salts. According to this author 
three drops of a solution of calcium chloride are sufficient to curdle 
ten cubic centimeters of fresh milk at 70° to 75° C. He further 
observed that while a very slight acidity seems to favor the coagula- 
tion by calcium salts it is by no means essential to the process, since 
it can be brought about even in faintly alkaline milk. 
Finally, in the presence of soluble calcium salts the paracasein 
resulting from the action of rennin is precipitated in the form of an 
insoluble calcium salt containing calcium phosphate, either in loose 
