Vines . — The Proteolytic Enzyme of Nepenthes. 569 
• Increment acide.’ Now, no one has ever asserted that 
liquid from unopened pitchers will digest cubes of white of 
egg ; it would be as reasonable to expect an extract of gastric 
mucous membrane to digest in the absence of an adequate 
supply of acid. Had he added a few drops of -2% HC1 
to the liquid, I feel certain that his results would have been 
altogether different ; this is, in fact, an experiment which 
ought to have been made before he allowed himself to form 
any definite opinion. 
Tischutkin’s observations certainly appear to be more 
formidable than those of Dubois. It is impossible for me 
to attempt any adequate criticism of them, as the . original 
paper is inaccessible to me, and the abstract in the Bot. 
Centralblatt does not give the details of the experiment with 
sufficient minuteness. It would appear, however, that Goebel’s 
observations counterbalance them ; and to his I would add 
the weight of the following of my own. 
Activity of Pitcher-liquid. 
In these experiments the material used for digestion was 
chiefly well-washed blood-fibrin preserved in a mixture of 
one part pure glycerin and two parts distilled water : coagu- 
lated egg-albumen was used but rarely, inasmuch as it is 
much more resistent to digestion than is fibrin, and the action 
is relatively slow. The fibrin preserved in glycerin may be 
regarded as free from Bacteria, in view of the results obtained 
by Copeman 1 with regard to the antiseptic action of glycerin. 
As regards Dubois’ objection to the use of fibrin in these 
digestive experiments, it is, I think, sufficiently met by the 
fact that I have frequently made control-experiments with 
tubes containing only dilute HC1 and fibrin, but no pitcher- 
liquid, and have invariably found that by the time that the 
fibrin in the tubes containing the pitcher-liquid had com- 
1 Copeman and Blaxall, Experiments on the Action of Glycerine upon the 
Growth of Bacteria; Brit. Assoc. Report, 1896. 
