Vines . — The Proteases of Plants {IIP). 181 
After 24 hours' further digestion the reaction of No. 2 had become slightly acid, 
those of Nos. 3 and 4 remaining alkaline : the tryptophane-reactions were : — ■ 
1. 2. 3. 4 - 
strong strong strong marked 
After 24 hours’ further digestion the reaction was still alkaline in Nos. 3 and 4 : the 
tryptophane-reaction had become very strong in Nos. 1 and 2, and was unchanged in 
Nos. 3 and 4. 
Conclusion : peptolysis not inhibited by distinct alkalinity, though certainly 
retarded; nor is the intensity of the tryptophane-reaction diminished by long- 
continued digestion with alkali. 
The second experiment confirms the first as regards peptolysis. It 
appears that though alkalinity retards peptolysis to begin with, the process 
eventually attains considerable activity. 
Taking the results of the two experiments together, it is clear that 
peptolysis has a wider reaction-range than fibrin-digestion : in fact the 
latter process is confined, as in Yeast, to about natural acidity. 
The comparison of my results with those of Weis raises points of 
considerable interest. Our methods of experiment differed in almost every 
respect : Weis worked with a strong aqueous extract, I with a more dilute 
NaCl-extract : he employed mainly vegetable proteids (glutin and legumin) 
as the material for digestion, I used fibrin and Witte-peptone of animal 
origin ; and the means of estimating digestive activity were altogether 
different. Yet we both come to the conclusion that two distinct proteases 
exist in Malt. His statement is that two stages can be distinguished in 
the proteolysis effected by Malt, a peptic stage and a tryptic stage ; and 
that these two stages are the result of the action of two enzymes, a peptase 
and a tryptase, since they are diversely affected by external conditions. 
1 regard the two enzymes as being respectively a peptase and an ereptase 
(not a tryptase) : but the difference between us is more apparent than real. 
For, on another page of his work ( 18 , p. 234), Weis discusses the action 
of the tryptase, and raises the question whether or not it can peptonize as 
well as peptolyse. On the analogy of animal trypsin, this might, he 
admits, be the case : but he expresses a doubt if animal trypsin be really 
a single protease : so he leaves the question open. However, in a foot- 
note, he alludes to Cohnheim’s discovery of erepsin in a manner suggesting 
that he thinks his ‘ tryptase ’ may be an enzyme of that nature. 
We agree, not only in this cardinal point, but also generally in the 
conclusion that alkalinity retards peptolysis : though my experiments go 
somewhat further than his, and show that in an alkaline liquid peptolysis 
is eventually active. The reason of this lies in the difference in the relative 
duration of our experiments. Weis’s determinations were made after only 
2 hours’ digestion ; mine after at least 24. Had his experiments been more 
prolonged, his results would, no doubt, have been in accordance with mine. 
