345 
He also arrived at the conclusion from his study of the influence of 
salts on the coagulation of decalcified milk that the facts observed 
seemed to favor the theory that the curdling of milk depends in great 
part, though not entirely, on the rearrangement or rendering availa- 
ble of its mineral constituents. He succeeded in showing that fresh 
milk can not precipitate paracasein solutions nor can it prevent their 
precipitation by calcium chloride. Hence it would seem that the 
calcium salts of fresh milk are in some way altered through the action 
of rennin, thereby becoming capable of precipitating paracasein. 
He concludes therefore that in the rennin coagulation of milk the 
rennin has the power in some way to render available the calcium 
salts (die calcium Salze frei zu machen), since without this change 
no coagulation is possible. Similarly Briot (14) maintains that rennin 
acts less on the caseinogen than on the calcium phosphate of milk. 
While this extreme view is probably incorrect it is certain that the 
majority of chemists are agreed regarding the necessity of calcium 
salts for the rennin coagulation of milk. That suck is the case is 
evident not only from the earlier investigations of Hammarsten but 
also from later and more exact observations by Arthus and Pages (15), 
Courant (16), Ringer (17), Loevenhart (18), Edmunds (19), Benja- 
min (20), Soldner (21), Laqueur (22), and others. 
It has also been established by the work of Courant (23) that the 
reaction of milk is not altered during the rennin coagulation. 
The question still remains to be considered, How does the rennin 
act on the caseinogen and in what way is the latter altered through 
the action of the ferment? These questions have been exhaustively 
considered by Laqueur (24), who has arrived at the conclusion that 
from the slight differences between caseinogen and paracasein thus 
far made out it is impossible to arrive at an unequivocal explana- 
tion of the coagulation of milk by rennin. This author is inclined 
to believe, however, that Hammarsten’ s original explanation of the 
process is perhaps, all things considered, the best we have. Accord- 
ing to this explanation the rennin acts by splitting the caseinogen 
into a larger molecule, paracasein, and a smaller molecule, the 
whey-pro teid (molkeneiweiss), also called hemicaseinogen albumose 
(Arthus and Pages). (Fuld (24a) has recently suggested the name 
whey-albumose for the soluble proteid produced in the rennin coagu- 
lation of milk.) This view also derives support from the more recent 
researches on the subject by P. T. Muller (25), who found whey- 
proteid in the milk serum only after rennin coagulation and not 
after the milk had been coagulated by acids or lactoserum. Simi- 
larly, unpublished analyses by W. Laqueur (26) and an experiment 
by Rotondi (27), also indicate the splitting off of a soluble nitrogenous 
compound from caseinogen during the rennin coagulation of milk. 
