215 
Vines .— The Proteases of Plants (VII). 
Experiment i. A i % extract: it gave no precipitate on boiling nor on adding 
HN 0 3 : distinct xanthoproteic reaction and distinct biuret, but no tryptophane- 
reaction. 
40 c.c. digested 0-2 grm. of fibrin in about 70 hours, the liquid then giving 
distinct biuret and marked tryptophane reactions. 
40C.C., to which 0-2 grm. Witte-peptone was added, gave marked tryptophane- 
reaction in 21 hours. 
Experiment 2. A 5 % extract. Some observations were made with the object 
of obtaining information as to the nature of the proteins present. A portion of the 
extract gave a dense precipitate on boiling: the filtrate still gave evidence of the 
presence of protein: it was saturated with ammonium sulphate and boiled, a dense 
precipitate being formed: the filtrate from this precipitate gave no further precipitate 
on boiling and no biuret-reaction. Hence it appears that absolute diastase contains 
an appreciable quantity of coagulable proteins as well as albumoses. 
40 c.c. of this extract digested o-i grm. fibrin within 22 hours, the liquid giving 
strong tryptophane-reaction. An autolysis experiment, carried on simultaneously, 
gave evidence, by a marked tryptophane-reaction, of the digestion of the native 
proteins. 
Having thus ascertained that watery extracts of absolute diastase can 
digest the native proteins, fibrin, and Witte-peptone, the investigation of the 
effect of variations in the reaction of the liquid upon the digestive processes 
was undertaken. 
Experiment 3. A 5 % extract used: it was distinctly acid, and gave a biuret- 
reaction, but no tryptophane. 
In each of 4 bottles were put 35 c.c. of the filtered extract : to No. 1 nothing was 
added; to No. 2, 0*2 grm. of fibrin; to No. 3, 0*2 grm. of fibrin and HC 1 to 0-12 % ; 
to No. 4, o-2 grm. of fibrin and Na 2 C 0 3 to about o-6 %. 
After 24 hours’ digestion in the incubator the results were—No. 1, the liquid 
gave a slight biuret-reaction ; No. 2, the fibrin had been partly digested, and the 
biuret-reaction was strong; No. 3, much the same as No. 2; No. 4, fibrin unaltered, 
biuret-reaction slight. 
24 hours later, the fibrin had almost entirely disappeared in Nos. 2 and 3. and 
the biuret-reaction was strong; the fibrin in No. 4 had been slightly attacked, and the 
liquid gave a distinct biuret-reaction, as did also that in No. 1. The tryptophane-test 
was then applied to all the liquids : the reaction was marked in Nos. 1 and 2 ; strong 
in No. 3 ; distinct in No. 4. 
These results show that an acid reaction of the liquid promotes both 
the peptonizing and the peptolyzing action of the proteases, whereas 
alkalinity retards both. They are confirmed, as regards peptolysis, by the 
following experiment with Witte-peptone :— 
Experiment 4. 30 c.c. of a 5 % filtered watery extract were put into each of 
4 bottles: to No. 1 nothing was added ; to No. 2, 0*2 grm. Witte-peptone; to 
