153 
Vines. — The Proteases of Plants (II). 
Since then I have made further investigations in this direction, and 
I avail myself of this opportunity to place them on record. I have con- 
firmed my previous results in many of the cases mentioned above, and have 
extended them to the Lime (Tilia vulgaris ), the Rhubarb (Rheum officinale 
and undulatum ), and Phytolacca decandra . The observations on Rheum 
and Phytolacca present features of sufficient interest to justify special 
mention. 
Rheum officinale and undulatum. 
These leaves were selected with the object of testing the digestive 
activity of tissues known to be strongly acid. 
In preparing the leaf for the experiment, the petiole and the lamina 
were kept separate : on grinding in the mincing-machine, a quantity of 
clear acid liquid was obtained from the petioles ; a watery extract was 
made of the lamina, and strained through muslin : the liquids were strongly 
acid. The earlier experiments gave a purely negative result : e. g. — 
40 c.c. of petiole-liquid were put into each of two bottles : to the one 0-2 grm. of 
fibrin was added, to the other 0-5 grm. of Witte-peptone ; the antiseptic was toluol 
1 % ; two similar bottles of lamina-extract were prepared. After digestion for about 
70 hours the fibrin was unaffected, and no tryptophane-reaction could be detected in 
any bottle. 
It then occurred to me that possibly digestive action had been inhibited 
by the acidity of the liquids. I therefore made an experiment in which 
excess of CaC 0 3 had been added to the liquids, but the results were still 
negative. 
I repeated the experiment with the modification that the tissue was 
extracted with water for several hours after mincing : the effect was that 
the bottles containing Witte-peptone gave more or less distinct tryptophane- 
reaction. The inference to be drawn seemed to be that the protease is not 
readily to be extracted from the tissues of the Rhubarb. Acting on this, 
I made experiments in which the minced tissue itself was used, with 
complete success, e. g.— 
250 grms. of lamina were minced, a little distilled water was added, and the 
mixture left to stand for 20 hours; the liquid was then strained through muslin; 
about 200 c.c. were obtained, giving no tryptophane-reaction. Four bottles, of 100 c.c. 
each, were then prepared as follows : — 
No. 1. 100 c.c. strained liquid +1 grm. Witte-peptone; 
„ 2. „ „ „ „ + 5 grms. CaC 0 3 ; 
,, 3. 10 grms. lamina, 100 c.c. distilled water + 1 grm. Witte-peptone; 
„ 4. „ „ „ „ „ +5 grms. CaC 0 3 . 
Toluol was added to 1 %. 
After 22 hours in the incubator, the tryptophane-reactions were : — 
No. 1, no reaction (liquid acid); No. 2, no reaction (liquid neutral); 
„ 3, strong „ „ ; „ 4, marked „ 
