Vines . — The Proteases of Plants . 295 
After about 20 hours in the incubator (temp. 38-40° C.) the tryptophane- 
reactions were: No. 1, marked; No. 2, strong; No. 3, faint. 
A repetition of the experiment, using chloroform-water as the liquid, gave the 
same results. 
A somewhat similar experiment was made with the object of ascertain- 
ing if so prolonged a period of digestion were necessary for autolysis. 
Experiment 2 . 40 cc. of an intimate mixture of 20 grms. ground yeast with 
200 cc. of distilled water were placed in each of 5 bottles, to each of which 
toluol (1%) was added; the contents of the bottles were then varied as follows: — 
No. 1, nothing further added; No. 2, HC 1 to 0-05 % ; No. 3, HC 1 to o*i %; No. 4, 
HC 1 to 0-2 % ; No. 5, Na 2 C 0 3 to 0-5 %. 
After 2 \ hours in the incubator the tryptophane-reactions, on treating 5 cc. 
of the liquids with equal vol. of chlorine-water, were No. 1, very strong ; No. 2, dis- 
tinct; No. 3, marked; No. 4, distinct; No. 5, which was distinctly alkaline, strong: 
further addition of chlorine-water did not intensify the reaction in any case. 
The following morning, after 20 hours more in the incubator, the tryptophane- 
reaction of Nos. 2 and 4 had become strong. 
From this it appears that autolysis is a rapid process, a conclusion 
confirmed by another experiment in which one of two bottles, each contain- 
ing 2 grms. dried yeast and 40 cc. distilled water, was kept for one hour in 
the incubator at 38°C., whilst the other bottle remained on the laboratory 
table at about n°C. At the end of this time the contents of the former gave 
a distinct tryptophane-reaction, whilst those of the latter gave no reaction. 
It appears, further, that autolysis can proceed within a wide range 
of alkalinity and acidity. The limits of this range were more nearly 
approached in the following experiment, which was of short duration : — 
Experiment 3 . 40 cc. of a mixture of 20 grms. dried yeast with 400 cc. distilled 
water, and toluol to 1 %, were placed in each of 9 bottles, the contents of which were 
varied as follows: — No. 1, nothing further added; No. 2, added 2 grms. precipitated 
chalk ; No. 3, added Na 2 C 0 3 to 0-5 % ; No. 4, added Na 2 C 0 3 to 1 % ; No. 5, added 
Na 2 C 0 3 to 2 %; No. 6, added HC 1 to 0-05 % ; No. 7, added HC 1 to o-i % ; No. 8, 
added HC 1 to 0-2 % ; No. 9, added HC 1 to 0-5 %. 
After 4 hours in the incubator at 38° C., 5 cc. of each of these various liquids, 
treated with an equal volume of chlorine-water, after acidification with acetic acid 
where necessary, gave the following tryptophane-reactions : — Nos. 1 and 2, very 
strong; No. 3, which was neutral before acidification, gave a strong reaction, as 
did also No. 4, which was alkaline ; No. 5, which also was alkaline before acidification, 
gave only a distinct reaction ; Nos. 6 and 7 gave a strong reaction ; No. 8 a distinct 
reaction ; No. 9 no reaction. 
The limit of acidity is here definitely indicated, the absence of the 
tryptophane-reaction proving that proteolysis did not take place in the 
presence of HC 1 added to 0-5 °/ o . The limit of alkalinity was not actually 
reached, though the retarding effect of 2 °/ o Na 2 C 0 3 was sufficiently 
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