302 
Vines. — The Proteases of Plants. 
With regard to the relation between the digestive activity of a mixture 
and the quantity of yeast contained in it, I found to begin with that 50 cc. 
of a mixture of chloroform-water with 1-25% yeast did not digest 0*2 grm. 
fibrin in 70 hours. This relation, as well as the action of acid and alkali, is 
further determined in the following comprehensive experiment : — 
Experiment 2. Mixtures were prepared of toluol-water (1 %) with 2-5 %, 5%, 
10 %, and 20% dried yeast respectively. 40 cc. of each of these mixtures were put 
into each of 3 bottles, to one of which nothing was added, to the second Na 2 C 0 3 
to 2%, to the third HC 1 to 0-5%, and 0-3 grm. fibrin to each bottle. After 22 
hours’ digestion the results were : — 
Added nothing . 
20 % bottles; fibrin gone 
10 „ „ „ gone 
5 „ „ „ not gone in any : 
2-5 ,, „ „ not gone in any : 
after further digestion for 25 hours — 
20% bottles; fibrin — 
,, ,, — 
5 » » » gone 
2*5 „ ,i „ gone 
NafX) y 
gone 
gone 
not gone 
not gone 
HCl 
not gone 
not gone 
not quite gone 
not gone 
not gone 
not gone 
after further digestion for 28 hours— 
20% bottles; fibrin — — 
10 ,, ,, ,, 
5 » ,» „ — not gone 
2.5 „ „ „ — not gone 
24 hours later, when the experiment closed, the results were the 
gone 
not gone 
not gone 
not gone 
same. 
These results suffice to indicate the relation between the digestive 
action on fibrin of yeast-mixtures of different strengths, and the degree 
to which digestive activity is affected by fairly strong acid and alkali 
in each case. Those afforded by the bottles containing 0-5 °/ o HCl are 
of special interest in relation to Bokorny’s experiments, in which, as I have 
already pointed out (see p. 293), the conditions seem to have been such as 
to prevent any digestion at all of the added proteid. This criticism applies 
more particularly to those of his experiments (Nos. 1-8) in which the 
amount of yeast present was 5 °/ o , the strength of acid o. 5-1 °/ o H 3 P 0 4 , and 
the proteid to be digested (ten times the weight of the yeast employed) the 
meat-residue from the preparation of Liebig’s extract. The facts upon which 
I base this criticism are supported by other results, subsequently described, 
obtained in experiments with yeast-extracts. It is more difficult to criticize 
Bokorny’s further experiments (Nos. 9-15), in which proteids of vegetable 
origin (prepared from Pea-flour, Soja-bean-meal, and Rape-cake) were the 
material to be digested, since the quantitative relations are not clearly 
stated : but, in view of the small amount of digestive products obtained, 
