68 THE AMINO ACIDS 



tion placed in the incubator, there was an almost com- 

 plete disappearance of proteose and peptone, which of 

 course could not be ascribed to further decomposition 

 since gastric juice does not hydrolyze proteoses and 

 peptones to amino acids, at least during such a short 

 period. The conclusion drawn was that the proteoses 

 and peptones disappeared because of their synthesis 

 to protein. In other experiments Hofmeister demon- 

 strated that the intestine possesses the same property. 

 Glaessner repeated and confirmed Hofmeister's inves- 

 tigation. On the other hand, Embden and Knoop 

 failed to find any evidence of protein synthesis. They 

 employed the normal intestine and also the intestine 

 from which pancreatic juice was excluded by ligature 

 of the duct. The evidence for resynthesis of protein 

 in the gastric or intestinal mucous membranes is not 

 convincing and one must obtain other than negative 

 evidence before the idea of such a protein resynthesis 

 can be accepted. 



Plastein Formation. It has been observed repeatedly 

 that when solutions of proteoses are brought into con- 

 tact with rennin a precipitate called plastein forms. 

 Various views as to its formation have been held. It 

 has been assumed by some that plastein is a new syn- 

 thetic product formed from the proteoses a new pro- 

 tein, by others a resynthesis of the proteoses to the 

 original protein from which they were derived, and by 

 still others as a digestion product on its way to com- 

 plete solution. The results of the most searching 

 investigations concerning the nature of plastein incline 



