348 
tion it has been pointed out by Herwerden (34a) that hydrogen 
ions are not necessary for the rennin coagulation of milk or of solu- 
tions of caseinogen containing calcium. 
(3) That in the rennin coagulation of milk two active agents are 
concerned, a soluble ferment, rennin, and calcium ions; that is, solu- 
ble calcium salts. 
According to Hammarsten the caseinogen is resolved by rennin 
into paracasein and whey proteid. Through the action of calcium 
ions (soluble calcium salts), the former is then precipitated as the 
curd (Kase), the latter remaining in solution. According to Fuld 
and others the change of caseinogen into paracasein is a molecular 
rearrangement. According to Courant the dicalcium caseinogenate 
is so altered by rennin that by contact with soluble calcium salts a 
precipitate (the curd) is produced. According to Loevenhart the 
rennin renders the calcium salts of milk available for the coagulation 
of paracasein, which latter is formed from caseinogen also by the 
action of rennin, and which, according to this author, differs from 
caseinogen only in that it is composed of larger molecular aggregates. 
It will be observed that these several views regarding the precise 
mode of action of the rennin differ in some particulars. These dif- 
ferences can only be reconciled by further investigation. 
It has been shown by Soldner (35), Osborne (36), Courant (37), 
and others that caseinogen is an acid. According to Courant it 
forms three kinds of salts, namely, mono-, di-, and tri-caseinogenates. 
It also seems probable from Lehmann’s (38) investigations that the 
caseinogen exists in fresh milk in the form of a complex calcium 
salt containing calcium phosphate. According to this author the 
composition of this compound agrees reasonably well with the 
formula 
Ca 3 (P0 4 ) 2 .Ca.caseinogen. 
According to Courant (39) a solution can be obtained showing essen- 
tially the same alkalinity to lacmoid and the same acidity to phenol- 
phthalein 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 H 3 P0 4 - Ca 3 (P0 4 ) 2 + 2 Cas - OCa + 
\OH ‘ W 
Ca (H 2 P0 4 )j + 12 H..O. 
In other words, the mixture or compound 
/Oil 
[Ca 3 (P0 4 ) 9 + 2 Cas - O. r + Ca (H 2 P0 4 )J 
\0>^a 
