1905] CALDWELL—ACTION OF BROMELIN 41L 
After being dried upon the water-bath at 40° C., the preparation 
was wholly soluble in water and was not autodigestive in any medium 
even after prolonged standing. It was active in faintly acid or 
alkaline solutions, though not at all in neutral media. This prepara- 
tion was used throughout the experiments. 
In order that the results might not be rendered inaccurate through 
the use of preparations of unequal purity, all the enzyme used was 
prepared at one time and thoroughly mixed after drying. From 46 
pineapples of average size, 16.4** of filtered juice were obtained, 
which yielded 14.88™ of the enzyme dried at 40° C. This was kept 
in a calcium chlorid desiccator and from time to time compared 
with fresh preparations, but no deterioration occurred in the period 
covered by the experiments. 
The enzyme was most active in solutions of alkalinity equaling 
m/30-m/40 NaOH, and was considerably less active in acid solu- 
tions irrespective of strength. Its action was wholly inhibited by 
m/1to HNO, or H,SO,, m/15 HCl, NaOH, or KOH, or m/20 NH,OH. 
The fact that the enzyme had been found most active in acid and 
neutral solutions by CHITTENDEN, while my own preparations were 
markedly more active in alkaline than in acid media and showed 
only the slightest trace of activity in neutral solutions, led me to a 
very careful examination of this point. CHITTENDEN’S statement 
of his method was followed in making a number of preparations. 
Pineapples of varying ripeness were chosen, upon the hypothesis 
that a change in the nature of the enzyme might occur with the ripen- 
ing of the fruit, but all of my preparations agreed perfectly in requiring 
an alkaline medium for optimum action, very much less action cccur- 
ring in acid media. One preparation from very immature fruits 
showed faint activity in a neutral solution. This difference from 
the results of CHITTENDEN’s examination seems explicable only on 
the ground that I have misunderstood his statement of his method 
of preparation; yet the method is simple and the statement is appar- 
ently lucid and exact enough to be followed without difficulty. 
ISOLATION OF THE ALKALINE ENZYME. 
Some of the facts observed in the preparation of the enzyme 
suggested that it might be in reality a mixture of two enzymes separ- 
