Vines. — The Proteases of Plants {VI). 9 
considerably, as if it had been fermenting : this occurred in all experiments with 
fresh Yeast. 
The mixture was put on a filter next morning, the filtrate dropping into a vessel 
containing 1 litre of alcohol. A portion of the filtrate was collected for examination, 
it was found to be clear, yellow, strongly acid, giving marked turbidity on boiling, 
less turbidity on adding HN 0 3 , strong xanthoproteic reaction, distinct biuret-, but no 
tryptophane-reaction : its digestive properties were that it acted quickly upon Witte- 
peptone, the digestion-liquid giving marked tryptophane-reaction in twenty-four hours, 
whilst its action upon fibrin was slower. 
The filtrate dropping into alcohol gave rise to a copious precipitate : the mixture 
was put on a filter, and the alcoholic liquid drained off. When filtration was com- 
pleted, the moist precipitate on the filter was found to weigh just over 1 5 grms. 
The precipitate was now mixed with 200 cc. distilled water, and left standing 
for some hours. The mixture was then filtered : the water did not appear to have 
dissolved much, if any, of the precipitate, and the filtrate had no digestive action on 
either fibrin or Witte-peptone. 
After having thus been washed with water, the precipitate was mixed with 150 cc. 
2 per cent. NaCl-solution : after standing for some hours, the mixture was put on a filter. 
The filtered NaCl-extract was neutral, opalescent, giving slight precipitate on 
boiling, and turbidity with HNO s , a slight xanthoproteic reaction, but no biuret. 
60 cc. of the filtrate were taken for experiment : 30 cc. were put into a bottle 
(a) with 0*2 grm. of fibrin and 0-2 grm. of Witte-peptone; the other 30 cc. were 
boiled and filtered, the liquid being made up to the original quantity by adding 
distilled water, and put into a bottle ( b ) with fibrin and Witte-peptone as before : a 
few drops of HCN were added to each. 
After twenty-four hours’ digestion, the fibrin had almost entirely disappeared in 
(<2) ; the liquid contents of it gave a considerable precipitate on boiling, somewhat less 
on adding HN 0 3 , but no tryptophane-reaction : the fibrin in ( b ) was quite unaltered, 
30 cc. of the filtrate were also put into each of three bottles ; the contents of the 
first were acidified to 0-06 per cent. HC 1 , those of the second to 0*45 per cent, 
citric acid, and those of the third were made alkaline to o*6 per cent. Na 2 Co 3 : 
o-2 grm. of fibrin was placed in each bottle, with a few drops of HCN. 
At the end of seventy-two hours in the incubator the fibrin was apparently 
Unaltered in all three bottles. It appears, therefore, that the reaction range of the 
peptase lies within the limits of acidity and alkalinity indicated in this experiment — 
a result which differs, as regards acidity, from that obtained by Hahn and Geret (see 
p. 7), the discrepancy being due, no doubt, to the presence of a considerable amount 
of protein in their liquids; but agrees fairly with my previous results (17, pp. 302-3). 
By this method, which is the same as the supplementary method applied 
to the investigation of papain (see p. 5), it was possible to prepare a liquid 
which digested fibrin, but had no action on Witte-peptone ; a liquid, there- 
fore, which contained only peptase in solution. 
The conclusion to be drawn from my experiments upon Yeast is that 
the cells contain two proteases, peptase and ereptase. The so-called 4 endo° 
