INDENTITY OF PEPSIN AND RENNIN 31 



school) have developed the idea that pepsin and rennin are 

 fundamentally identical ; that the lab-action is nothing else 

 than the reversed synthetizing manifestation of the same 

 ferment which normally behaves as a peptic protein cleav- 

 age-enzyme. This view undoubtedly is an attractive one, 

 and meets our demand for simplification of our concepts of 

 complicated natural phenomena. The great interest mani- 

 fested in this view is probably explicable on this basis. An 

 unusually large number of comprehensive researches have 

 been devoted within recent years to this question of the 

 identity of pepsin and lab-ferment. Pawlow's many associ- 

 ates 87 are constantly directing attention to the distinct 

 parallelism between the action of pepsin and lab. They 

 have been unable to separate the two ferments either by dif- 

 fusion, 88 nitration 89 or by electric conduction. 90 Hammer- 

 sten and very many other authors, 91 on the other hand, have 

 unquestionably produced in different ways solutions of 

 pepsin which no longer coagulate milk, and, too, lab solutions 

 which no longer manifest any peptic ability. An American 

 writer 92 has demonstrated that on passing an electric cur- 

 rent under certain conditions through a fluid containing both 

 rennin and pepsin the latter will be completely destroyed 

 while the lab remains unchanged. The physiologist Duc- 



w Cf. J. W. A. Gewin (Physiol. Instit., Utrecht.), Zeitschr. f. physiol. 

 Chem., 54, 32, 1907; W. S'awitsch, ibid., 55, 84, 1908; W. van Dam, ibid., 64, 

 316, 1910; Th. J. Migay and W. Sawitsch, ibid., 63, 405, 1909; W. Sawitsch, 

 ibid., 68, 13, 1910. 



88 R. 0. Herzog (Karlsruhe), Zeitschr. f. physiol. Chem., 60, 306, 1909. 



88 C. Funk and A. Niemann, Zeitschr. f. physiol. Chem., 68, 263, 1910. 



90 C. A. Pekelharing and W. E. Ringer, Zeitschr. f. physiol. Chem., 75, 

 282, 1911. 



W O. Hammersten, Zeitschr. f. physiol. Chem., 56, 18, 1908; 68, 119, 1910; 

 74, 142, 1911; S. Schmidt-Nielsen ( Hammersten's Laboratory), ibid., 68, 92, 

 1906; A. Rakoczy, ibid., 68, 421, 1910; J. F. B. van Hasselt, ibid., 70, 171, 

 1910; A. E. Porter, Journ. of Physiol., 42, 389, 1911; L. Blum and W. Bohme, 

 Hofmeister's Beitr., 9, 74, 1906; A. E. Taylor, Journ. of Biol. Chem., 5, 399, 

 1909; A. Rakoczy (Kiew), Zeitschr. f. physiol. Chem., 68, 421, 1910. 



M W. E. Burge (Johns Hopkins Univ.), Amer. Journ. of Physiol., 29, 

 330, 1912. 



