418 BOTANICAL GAZETTE [JUNE 
2. The effects of poisons vary with the purity of the preparation 
used, slight amounts of proteid impurities rendering necessary an 
enormous increase of concentration in order to inhibit action. 
3. The toxic strengths of the salts used maintain a constant 
relationship irrespective of the purity of the enzyme used, 7. e., silver 
is always most poisonous, copper third, zinc sixth, and so on. 
4. Bromelin, when prepared in a relatively pure condition is 
not at all autodigestive, the presence of some proteid of the juice 
apparently being a prerequisite for such action. 
5. Such preparations appear to be in reality a mixture of two 
enzymes, one active in alkaline solutions, slightly more resistant 
to poisons, and twice as great in amount as the other, which is active 
in acid media and is destroyed by heating to 65° C. in saline solution. 
6. The limits of toxicity and non-toxicity are somewhat. more 
clearly defined than has been the case in experiments upon living 
organisms (5, II, 12, 18, 19, 2 
7. The results obtained agree in general with MATHEWS’S arrange- 
ment of the metals upon the theory that ‘‘the affinity of the atom 
or ion for its electrical charge is the main factor determining its 
physiological action.’”” Cadmium in my experiments occupies the 
position it should hold in accordance with this theory, while barium 
is far out of place.* 
My sincere thanks are due to Dr. B. E. Lrvincston, at whose 
suggestion the work was begun, for much help in its inception, and 
to Dr. C. R. Barnes for assistance in its progress and completion. 
* Experiments undertaken in order to determine more conclusively the place to 
barium are still in progress. I have found it only relatively less poisonous 
than zinc in every case, whether bromelin,: papain, or animal trypsin were the 
enzyme u 
THF UNIVE RSITY OF CHICAGO. 
LITERATURE CITED. 
I. Bourque or, Les fermentations. Paris. 1 
2. CHITTENDEN, MENDEL, and McDermort, Papiin proteolysis. Am. Jour. 
Physiol. 1:255. 1808. 
3- CHITTENDEN, R. H., The enzyme of the pineapple. Trans. Conn. Acad. 
8:36. 1801. 
1894. 
, The enzyme of the pineapple. Jour. Physiol. 15:290- 
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