30 GASTRIC DIGESTION OF PROTEINS 



notice, bearing upon the participation of a hitherto neglected 

 factor, that of bacterial infection, in the process of lab- 

 coagulation. They point out that sterile milk will not 

 coagulate in sterile vessels if treated with sterile rennin; 

 but merely touching the milk with the non-sterile finger or 

 the addition of a few drops of ordinary milk will cause 

 curding. 



Much thought has been devoted to the formulation of an 

 acceptable conception of the physiological purpose of the 

 lab-process. That an eventual change of the milk intro- 

 duced into the stomach into a firm curd, so that this can pass 

 into the intestine only bit by bit, gradually, thus protecting 

 the intestine against being flooded with food-proteins, and 

 that this in many animals is of importance in the nourish- 

 ment of the young, all this goes without question. There 

 is reason to question, however, whether the greatest value of 

 the rennin, which is found widely distributed in the digestive 

 organs of vertebrates, many invertebrates and, too, in the 

 juices of many plants, 85 should not be sought for in an alto- 

 gether different direction. 



Plastins. Observations of A. Danilewski and his numer- 

 ous students 86 that rennin (and also extracts of intestine 

 and of pancreas) gives rise to precipitation in solutions of 

 products of peptic digestion suggest that these precipitates 

 may be considered as an expression of a synthetic fermenta- 

 tion, possibly directed toward the regeneration of the split 

 protein. But the attractive prospect that in plastins we are 

 seeing intermediate products of a fermentative protein 

 synthesis, has unfortunately all too soon met the fate of the 

 most of the brilliant expectations of this world. 



Question of the Identity of Pepsin and Rennin. Obser- 

 vations of this kind (mainly from Pawlow and his 



M W. Biedermann, Handb. d. vergleich. Physiol., 2', 1289, 1911. 



M Kurajeff, Lawrow, Lukomnik, NUrnberg, Okunew, Salaskin, Sawjalow, 

 Schapirow and others. Cf. also R. 0. Herzog, Zeitschr. f. physiol. Chem., 39, 

 305, 1903; H. Bayer (Hofmeister's Laborat.), Hofmeister's Beitr., 4, 554, 1903. 



