ALBUMINS OR PROTEINS. 207 



salts. The latter property is therefore dependent on the presence of cal- 

 cium salts, and has no direct relation with the rennin as such. The albu- 

 min formed, para-casein, differs essentially from casein, inasmuch as it is 

 precipitated by calcium salts. The precipitate contains large amounts 

 of calcium phosphate. We do not know what relation this salt has to 

 the curdling. 



According to the general conception, the pepsin action follows the 

 precipitation of the para-casein, disintegrating it in the same manner as 

 it does the remaining proteins. The phosphoric acid portion, the so- 

 called pseudonuclein (a compound as yet insufficiently investigated), is 

 thrown out at this stage. It does not possess any of the ordinary com- 

 ponents of the nucleins. The purpose of the rennin action is not at all 

 clear. It is certainly significant that we always find evidence of the 

 activity of rennin wherever there are proteolytic ferments. Rennin is found 

 in the intestine and in the organs. It cannot be denied that the concep- 

 tion that the activity of rennin is to be regarded as being an hydrolytic 

 attack, and the precipitation by the calcium salts as only an intermediate 

 effect, depending on the specific characteristics of the first cleavage-products 

 of casein, these being then subjected to the further disintegrating action of 

 the pepsin, is certainly a very attractive one. The behavior of casein 

 during digestion is thus removed from its special position, while the 

 assumption of Pawlow and Parastschuk that rennin and pepsin are iden- 

 tical is given a further support, to be sure in the sense that it is a case of 

 one and the same kind of fermentation, and not that of two different 

 actions. These processes are still very obscure. 



The opinion has often been expressed that pepsin and rennin are not 

 simple, individual ferments. The various species of animals are supposed 

 to possess different kinds of ferments. The rennins from human beings 

 and from swine are supposed to be different from that obtained from 

 the calf. Bang 1 has isolated a rennin, parachymosin, from the stomach 

 of the calf, whose properties are essentially different from those obtained 

 from other sources. Not even the pepsins from different animals are 

 alike. Differences undoubtedly exist, which may possibly be due to the 

 nature of the different nutrient albumins supplied to the animals. As 

 long as we are not acquainted with the ferments as such, and are unable 

 to study their activity in uniform materials, it will be difficult to pass judg- 

 ment on the results obtained with different ferments. It is to be hoped 

 that the transference of such investigations to the complicated polypep- 

 tides of known structure and configuration will throw light upon this 

 subject. 



We must refer to another peculiar phenomenon as yet entirely unex- 



1 Pfliiger's Arch. 79, 425 (1900). 



