Vines. — The Proteases of Plants (V). 105 
In order to make sure that the more rapid action on fibrin of the 
NaCl-extract was not due to saline digestion, a control-experiment was 
made : 02 grm. fibrin was placed in a bottle with 70 cc. of 2°/ o NaCl- 
solution ; after remaining in the incubator for six weeks the fibrin was 
found to be quite unaltered. 
Experiment 3. The question as to the greater solubility of the 
fibrin-digesting protease in NaCl-solution was further investigated by the 
method of preparing a relatively stronger H^O-extract. 
10 grms. of seed were extracted with 100 cc. 2% NaCl-solution, and 20 grms. 
with 100 cc. distilled water : 50 cc. of each extract were put into separate bottles with 
o-2 grm. fibrin and a little HCN. After 24 hours the fibrin in the NaCl-bottle was 
broken up, that in the H 2 0 -bottle being unaltered ; after 48 hours the fibrin had 
nearly disappeared in the former, and was breaking up in the latter; after 72 hours 
there was still some left in the former, and but little in the latter ; after 96 hours the 
fibrin had completely disappeared in both. The tryptophane-reaction was strong in 
both, but distinctly stronger in the H 2 0 -bottle ; neither liquid gave any appreciable 
precipitate on boiling. The interesting observation was made that the H 2 0 -liquid 
gave only a trace of biuret-reaction, whereas that of the NaCl-liquid was as strong as 
at the beginning of the experiment. Subsequent special experiments on autolysis 
confirmed this result (see Experiment 5, p. 107). 
It appears from this experiment that the fibrin-digesting activity of 
the NaCl-extract was about the same as that of the H 2 0 -extract of twice 
the strength ; the digestive action of the former, though more rapid at first, 
was eventually overtaken by that of the latter, so that the complete dis- 
appearance of the fibrin occurred at about the same time in both. It may 
be concluded that a 2°/ o solution of NaCl dissolves about twice as much of the 
peptonizing protease from the seed as does an equal proportion of distilled 
water. But the possibility still remains that the greater digestive activity 
of the NaCl-extract maybe due, at least in part, to the direct action of the 
salt upon the process of digestion. The following experiment was made 
for the purpose of determining this point : — 
Experiment 4. 20 grms. of crushed seed were extracted with 125 cc. H 2 0 , an< 3 
10 grms. with half the quantity of 2% NaCl-solution. 
Three bottles, each containing 40 cc., were prepared as follows: — No. 1, 1120- 
extract; No. 2, H 2 0 -extract to which was added o-8 grm, NaCl (= 2%); No. 3, 
2% NaCl-extract: to each bottle were added 0-2 grm. fibrin and a few drops 
of HCN. 
After 24 hours’ digestion in the incubator the fibrin in No. 1 was apparently 
unaltered; in No. 2 it was breaking up; in No. 3 it had nearly all disappeared. 
24 hours later the fibrin was breaking up in No. 1 ; it was about half gone in No. 2 ; 
and had entirely disappeared in No. 3. 24 hours later it was reduced in No. 1, and 
had nearly disappeared in No. 2. 48 hours later the fibrin had not quite gone in 
No. 1, but had entirely disappeared in No. 2. Hence the fibrin was digested in No. 3 
