294 
Vines. — The Proteases of Plants. 
of maximum intensity; thus a standard of comparison for the other experi- 
ments in the same set was obtained. The quantity of chlorine-water 
required varies considerably, in relation, apparently, with the amount 
of tryptophane present : since an excess of chlorine destroys the reaction, 
it may be concluded that the more chlorine-water required, the greater the 
amount of tryptophane present. For instance, in an autolysis of a watery 
liquid containing 5°/ 0 dry yeast, I found that the addition of an equal 
volume of chlorine-water (say 5 cc. of each) gave the maximum trypto- 
phane reaction, when the digestion had been short (say 4-6 hours) : but 
when the digestion had been more prolonged (say 24 hours), it required 
twice the volume of chlorine-water to obtain a reaction as intense as 
that given as the result of the shorter digestion. It is also necessary 
to allow the tested liquid to stand for several minutes before estimating 
the intensity of the reaction, for it takes an appreciable time to develop. 
The liquid to be tested must, of course, have an acid reaction. 
In the experiments with fibrin, the main object was the determination 
of peptonizing activity : accordingly the crucial test was the total dis- 
appearance of the fibrin, which was consequently supplied in small quantity 
(usually about 0-5 grm. to 100 cc. of liquid). The fibrin had been preserved 
in 5° % glycerin. 
The dried yeast, previously to an experiment, was ground to a fine 
powder in a hand-mill, and was then thoroughly triturated in a mortar with 
the water necessary to prepare the required digestive liquid. The resulting 
mixture was then either used as it was, or it was filtered at a low tempera- 
ture so as to prevent autolysis during the somewhat lengthy process, and 
the clear filtrate was employed. Toluol, to about 1 °/ o , was found to be 
the most unobjectionable antiseptic, though I obtained good results with 
others, such as chloroform, sodium fluoride, and hydrocyanic acid. It 
is important to state definitely that in no case did the freshly-prepared 
yeast-liquid, whether mixture or extract, give any tryptophane-reaction, 
thus proving that the yeast used contained no tryptophane to begin with. 
Autolysis. 
The fact that, under certain circumstances, the yeast can digest its 
own proteids is a familiar one. My object in experimenting upon it was 
to ascertain something more definite as to the conditions determining 
the activity of autolysis, and as to the nature of the enzyme by which 
it is effected. The following experiments will give an idea of the method 
adopted and of the results attained. 
Experiment 1. 1 grm. dried yeast placed in each of 3 bottles with 40 cc. 
distilled water: to No. 1 nothing further was added; to No. 2 was added 0*5 grm. 
precipitated chalk, to neutralize any free acid present; to No. 3, o-i grm. citric acid 
(=o-25%)’ 
