THE EFFECTS OF TOXIC AGENTS UPON THE ACTION 
OF BROMELIN. 
CONTRIBUTIONS FROM THE HULL BOTANICAL LABORATORY. 
LXXIII. 
JOSEPH STUART CALDWELL. 
HISTORICAL. 
ATTENTION was first directed to the existence of a proteolytic 
enzyme in the juice of the pineapple (Ananas sativus) by MaRcano 
(13). It wascalled bromelin by CHITTENDEN, who, with his pupils, 
examined it in some detail (3, 4). They prepared it from the expressed 
and filtered juice, after neutralization, by saturation with crystals of 
ammonium or magnesium sulfate or sodium chlorid, any of which 
precipitate the enzyme together with some proteid matter. The 
precipitate was dialyzed free from salt in running water, collected 
upona filter, and dried at 40° C. upon a water-bath. The flaky, whit- 
ish residue thus obtained consisted of the enzyme with some associ- 
ated proteid. It was soluble in water and active in acid or neutral 
solutions, very slightly or not at all in an alkaline medium. The 
sodium chlorid preparation was more active and greater in amount 
than the others, and was used throughout the experiments. Curt- 
TENDEN’S study was directed principally to a determination of the 
products of digestion of blood-fibrin, myosin, and coagulated egg 
albumen. These were found to be hemi- and anti-peptones, proto-, 
hetero-, and deutero-proteose, leucin, and tyrosin. The enzyme was 
thus determined to be tryptic in nature, and akin to other vegetable 
trypsins in that it acted best in an acid medium. 
PURPOSE. 
The experiments described in this paper were undertaken with 
a view to ascertaining whether a similarity existed between the 
effects of poisonous metals upon the action of an enzyme and those 
observed in experiments upon living organisms. While an immense 
amount of work has been done with plants and animals, the results 
are at variance, not even agreeing as to the most poisonous metal. 
1905] 409 
