346 
On the other hand, according to Duclaux (28), who analysed the 
filtrates obtained by filtering fresh milk and milk coagulated by ren- 
nin through a porcelain filter, the soluble nitrogen in the whey is 
not increased after rennin coagulation, nor is the composition of the 
whey altered in any way. That such is the case may be seen from 
the following results of his analyses of milk serum before and after 
coagulation by rennin. 
Experiment I. 
Experiment II. 
Normal 
milk. 
Milk coag- 
ulated by 
rennin. 
Normal 
milk. 
Milk coag- 
ulated by 
rennin. 
Lactose 
5.53 
5.53 
5. 37 
5. 64 
Soluble albumin 
.55 
.57 
.37 
.36 
Mineral matter 
. 54 
.52 
. 56 
.40 
Arrhenius (29) is of the opinion however that Duclaux’s experi- 
ments on this point are not convincing, since the whey proteid might 
have been retained by the porcelain filter, especially in the presence 
of the gelatinous paracasein. 
From his researches on the laws governing rennin coagulation Fuld 
(30) also arrives at the conclusion that the transformation of case- 
inogen into paracasein is only a molecular rearrangement, partaking 
of the nature of a monomolecular process. According to this author 
the rennin coagulation of milk is only a special case of the well-known 
phenomenon of the reciprocal suspension and precipitation of colloidal 
substances. Loevenhart (31) has also reached the conclusion that it 
is probable that caseinogen and paracasein are chemically the same 
substance, and that the observed differences existing between them 
depend upon the fact that paracasein exhibits a higher degree of 
association than caseinogen. In other words, paracasein consists of 
larger molecular aggregates than caseinogen, otherwise they are 
identical. These views are shared by other observers, among them 
Van Slyke and Hart (32). On the other hand Laqueur (33) from a 
consideration of these facts and the conduct of other colloidal sub- 
stances, comes to exactly the opposite conclusion, viz, that caseinogen 
is probably a higher colloid than paracasein. 
According to Laqueur (34) , the idea that paracasein is a more com- 
plex substance than caseinogen has also received support from 
Danilewski’s observation that rennin gives rise to a precipitate in solu- 
tions of albumoses. According to the Russian investigators by whom 
this reaction has been extensively studied this precipitate possesses 
the properties of a higher proteid. They therefore see in this change 
the synthesis of a complex substance from the products of assimila- 
tion, having the nature of naturally-occurring proteids, and find a 
ready explanation for the widespread occurrence of rennin in animals 
and plants which are in no wise concerned with the digestion of milk. 
