177 
Vines . — The Proteases of Plants (///). 
3 , p. 605). It is not surprising that the peptolytic enzyme should have 
been found to be less active in neutral or alkaline liquid than in acid, when 
it is remembered that the latex and the juices of the Papaw are acid. 
I have not attempted to determine the limits of alkalinity and acidity 
for other samples of papain : no doubt they would be found to vary 
considerably. But I know from previous experiments that the nature 
of the differential effect is essentially the same in all, under the same 
conditions. 
Ananas sativus. 
40 cc. of the expressed juice of a ripe Pineapple were put into each of 5 
bottles, 2 % of Witte-peptone having been previously added : 03 grm. fibrin was put 
into each bottle. To 2 of the bottles Na 2 C 0 3 was gradually added to the extent of 
7-5%, when a definitely alkaline reaction was attained: the contents of 2 bottles 
were left at natural acidity : to the fifth bottle HC 1 0-2 % was added. To a naturally 
acid bottle and to an alkaline bottle HCN 0*2% was added: to a similar pair of 
bottles NaF 1 % was added : there were thus 4 bottles containing an antiseptic, but 
no antiseptic was added to the HC 1 bottle. 
After 24 hours’ digestion in the incubator at 38° C. the fibrin had disappeared in 
all the bottles : the tryptophane-reactions were : — 
HCN acid, HCNalk. NaF acid. NaF alk. HCl 
marked none strong none strong 
Conclusion : peptolysis, but not fibrin-digestion, completely inhibited by 
alkalinity. 
A corresponding experiment made with juice diluted with equal volume of 
distilled water gave results of the same nature. In yet another experiment in which 
Na 2 C 0 3 was added to 2-5% (reaction still acid) and to 5 % (reaction slightly alkaline), 
a faint tryptophane-reaction was observed, showing that peptolysis was not altogether 
inhibited. 
The effect of alkalinity upon peptolysis is further demonstrated by the following 
experiment, in which three degrees of alkalinity were compared, and in which Witte- 
peptone was not added until after the completion of fibrin-digestion. 
50 cc. of juice were placed in each of 4 bottles with 1 % toluol and \ grm. 
fibrin: No. 1, contents of natural acidity; No. 2, slightly alkaline by addition of 
Na 2 C 0 3 to 4 % ; No. 3, more alkaline, Na 2 C 0 3 6 % ; No. 4, strongly alkaline, 
Na 2 C 0 3 8 %. 
After 24 hours’ digestion the results were: — 
i. 
2. 
3 - 
4. 
fibrin 
nearly gone 
gone 
gone 
attacked 
tryptophane-reaction 
faint 
faint 
none 
none 
after 48 hours’ digestion 
fibrin 
gone 
— 
nearly gone 
tryptophane-reaction 
faint 
faint 
none 
none 
