i57 
Vines. — The Proteases of Plants (//). 
pointed out, fibrin-digestion and the peptolysis of Witte-peptone are not 
always similarly affected by the various experimental conditions provided. 
For instance, Christy’s papain readily digested fibrin in the presence of 
NaF, whilst there was at the same time little or no peptolysis ; and the 
same was the case with Finkler’s papain and with weak Merck’s papain (E), 
in the presence of HCN. The converse does not come out quite so clearly : 
but there are indications, as for instance in the toluol-acid experiment with 
Christy’s papain (p. 154), of some degree of peptolysis with little or no 
digestion of fibrin. These facts are susceptible of two interpretations : — 
(1) that a single protease is present, capable of both fibrin-digestion and 
peptolysis, and that one or other of these activities may be more or less 
inhibited by the antiseptics : or (2) that two proteases are present in papain, 
which may respond differently and independently to the action of anti- 
septics. Of the two alternatives, the former is the one that seems to 
offer the greater difficulties. It is not easy to imagine how one part of 
the work of the protease could be arrested without the other : it is more 
natural to conclude that if the protease were affected at all, the whole of 
its functional activity would be interfered with. If, then, the second alter- 
native be accepted, the interesting conclusion is arrived at that papain 
contains a fibrin-digesting, but not peptolytic, protease of the nature of 
a pepsin ; as well as a peptolytic, but not fibrin-digesting, protease of the 
nature of an erepsin. If this be so, it will be the first clear demonstration 
of the existence of a pepsin in the Vegetable Kingdom. 
I do not claim that my experiments suffice to establish this conclusion 
beyond the possibility of doubt. But they at least indicate a method 
by which a physiological analysis of possible mixtures of enzymes may 
be effected. It is, I believe, by the application of this method to the fresh 
juices of the Papaw that the question will be settled for that plant. In the 
meantime I am applying it to the investigation of other plants, and have 
already obtained some confirmatory results in the case of the Hyacinth- 
bulb, of the Pine-apple, and of Yeast, of which I hope to give an account 
in a subsequent paper. An investigation of animal trypsin along these lines 
would, I believe, yield results of considerable interest. 
Digestion by Leaves. 
In a previous paper (7) I have given an account of some experiments 
upon the proteolytic action of the foliage-leaves of various plants, viz. : 
Spinacia oleracea , Dahlia , Mirahilis Jalapa , Tropaeolum majus , Prunas 
Laurocerasus , Ricinus communis , Helianthus tuberosus , Pelargonium zonale , 
Brassica oleracea , Holcus mollis, Phalaris canariensis , Apium graveolens , 
Scolopendrium vulgar e, Lactuca sativa. The conclusion to be drawn from 
those experiments was that the leaves could peptolyse but not peptonise ; 
in other words, that they contain an erepsin but no fibrin-digesting protease. 
