4 
Vines — The Proteases of Plants {VI). 
Digestive properties. 40 cc. of the filtrate digested 0-2 grm. fibrin within five hours, 
and also digested Witte-peptone, as shown by the tryptophane-reaction. 
The papain-residue (about 5 grms.) was removed from the filter, triturated in the 
mortar with 200 cc. dist. water, and the mixture filtered. 
Filtrate 2. The filtered H 2 0 -extract was clear and neutral, gave no ppt. or tur- 
bidity on boiling, or on adding HN 0 3 , and only a slight xanthoproteic reaction. 
Digestive properties. 40 cc. of the filtrate failed to digest 0*2 grm. of fibrin in forty- 
eight hours, and had no action on Witte-peptone. 
Hence it appears in this case, that, since ereptase is readily soluble in water, the 
papain-residue contained none of it : that, in fact, the whole of the ereptase had been 
dissolved out in the extraction with NaCl-solution. 
The papain-residue, after the extraction with H 2 0 , was extracted with 120 cc. 
of 2 per cent. NaCl-solution ; the mixture was allowed to stand for a short time, and 
was then filtered. 
Filtrate 3. The filtered NaCl-extract was colourless and neutral : it gave no 
turbidity on boiling, but a slight turbidity on adding HN 0 3 , a faint xanthoproteic 
reaction, no biuret-reaction, no tryptophane-reaction. 
Digestive properties . 35 cc. of the filtrate were put into each of three bottles, 
Nos. 1, 2, 3, the liquid placed in No. 2 having been previously boiled; to each bottle 
was added o-2 grm. fibrin ; and to Nos. 1 and 2, 0*2 grm. of Witte-peptone. 
Within twenty-four hours the fibrin had completely disappeared in Nos. 1 and 3, 
remaining unaltered in No. 2. The contents of No. 1 gave no tryptophane-reaction : 
those of No. 3 gave a ppt. on boiling and on adding HN 0 3 , and a good biuret- 
reaction, but no tryptophane-reaction. 
It is clear that the NaCl-extract, filtrate 3, contains a fibrin-digesting (pep- 
tonizing) enzyme, but no peptone-splitting (peptolysing) enzyme. 
A further experiment was made with the same papain-residue. It was extracted 
once more with 200 cc. 2 per cent. NaCl solution and filtered. 
Filtrate 4. The neutral filtrate gave no turbidity on boiling or on adding HN 0 3 , 
and but a slight xanthoproteic reaction. 
Digestive properties. An attempt was made to ascertain in what way, if any, the 
digestive properties of the fibrin-digesting enzyme are affected by the reaction of the 
medium. 
35 cc. of the filtrate were put into each of five bottles, Nos. 1-5 : to one bottle 
(No. 2), 0-2 grm. of Witte-peptone was added, just to make sure that no ereptase 
had been extracted; to all the others, 0-2 grm. of fibrin: the contents of No. 3 
were acidified to 0*1 per cent. HC 1 , those of No. 4 to 0*5 per cent, citric acid, and 
those of No. 5 were made alkaline to 0*5 per cent. Na 2 C 0 3 . 
After twenty-four hours’ digestion, the fibrin had disappeared in No. 5 (alkaline), 
and was much broken up in No. 1 (normal), whilst it was unaltered in Nos. 3 and 4 
(acid). The contents of Nos. 1 and 5 gave ppt. on boiling and on adding HN 0 3 , 
a strong xanthoproteic and a good biuret-reaction, but no tryptophane-reaction. 
After forty-eight hours’ digestion, the contents of No. 2 gave no tryptophane- 
reaction, thus proving the absence of ereptase : the fibrin in Nos. 3 and 4 was still 
quite unaltered. 
