CHAP. III.] GENERAL PHENOMENA OF PROTEOLYSIS BY TRYPSIN. 223 



reaction is feebly acid. The conditions for its activity are therefore 

 seen to be such as enable it. to exert its action under the three 

 possible sets of conditions which may and do prevail under varying 

 circumstances, in the small intestine. 



Ktihne asserted 1 that trypsin is injuriously affected by the 

 presence of hydrochloric acid when it is in greater proportion than 

 0'5 per 10QO, and the statement is correct, inasmuch as some 

 weakening of the digestive action results. It has, however, since 

 been shewn a that trypsin can exert its solvent action on fibrin under 

 conditions which would formerly have been considered impossible. 

 C. A. Ewald has observed trypsin proteolysis of fibrin 8 to go on in a 

 liquid containing 0'3 per cent, of HC1, and the observation has been, 

 in a measure, confirmed by Mays, in a research conducted in Kuhne's 

 laboratory *. 



It appears, however, that digestion of fibrin by trypsin can only 

 go on in dilute hydrochloric acid containing 0*3 per cent, of the acid, 

 if there be a large quantity of fibrin present. As will be pointed 

 out again, it is unquestionable that trypsin is gradually destroyed by 

 dilute acids, the. researches of Langley 5 having fully confirmed the 

 original statements of Kiihne, by shewing that a glycerin extract 

 of the pancreas when warmed for two and a half hours with a 

 solution containing 0'05 per cent, of HC1, loses a very appreciable 

 amount of its trypsin. 



The influence All observers have agreed in stating that the acti- 



of temperature vity of trypsin increases, within certain limits, with the 

 on the digestive temperature. 



tr^sta f Roberts 6 has carefully studied the influence of tem- 



perature upon the activity of trypsin, and states that 

 this increases to 60 C. and then rapidly falls, all action ceasing 

 between 75 C. and 80 C. 



The General Phenomena of Proteolysis by Trypsin. 



Since the first careful study by Kiihne 'of the action of trypsin on 

 proteids, blood-fibrin the very proteid which Kiihne used in his 

 earlier experiments has been chiefly employed for the same pur- 



1 Kiihne, Verhandlungen des Naturhist. Med. Vereins zu Heidelberg, Bd. 1. 



2 Engesser, "Beitrage zur therapeutischen Verwendung d. Bandspeicheldriise von 

 Schlachtthieren und deren Praparate," Deutsch. Archiv f. klin. Medicin, Bd. 24, 

 S. 539. 



3 C. A. Ewald, " Das Engesser'sche Pankreaspulver." Zeitschrift f. klin. Med., Bd. 

 1, S. 615. 



4 Karl Mays, " Ueber die Wirkung von Trypsin in Sauren und von Trypsin und 

 Pepsin auf einander. " Untersuchungen a. d. physiolog. Institut in Heidelberg, Bd. 3, 

 S. 378. 



5 J. N. Langley, " On the Destruction of Ferments in the Alimentary Canal." Journ. 

 of Physiology, Vol. 3, p. 263. 



6 W. Roberts, M.D., F.R.S., " On the Estimation of the Amylolytic and Proteo- 

 lytic Activity of Pancreatic Extracts." Proceedings of the Eoyal Society. 



