a. H. Chittenden — Ferments of Pineapple Juice. 28*7 



when blood fibrin, for example, is warmed with neutralized pine- 

 apple juice, or better, with a neutral solution of the isolated ferment 

 there is at first no sign of any digestive action whatever, but on 

 stirring or shaking the mixture, after a sufficient length of time, the 

 fibrin falls to pieces completely disintegrated with the production of 

 a more or less turbid fluid, after which its solution is fairly rapid, 

 although there invariably remains considerable insoluble matter, the 

 same as in an acid mixture. While this action of the ferment 

 resembles somewhat that of trypsin, there is never seen that pecu- 

 liar eating into the fibrin, so characteristic of the latter ferment; the 

 fibrin never has the appearance of being full of tiny holes, as if 

 bored by a host of worms, so often seen in a trypsin digestion. The 

 pineapple ferment appears simply to soften the fibrin with more or 

 less solvent action at the same time, so that when stirred or pressed 

 it breaks apart into larger or smaller pieces, these in turn under- 

 going a like change until the fibrin is thoroughly disintegrated and 

 the soluble portion dissolved. 



1. — Influence of the reaction of the fluid. 



As is well known, trypsin * and papain f act best in an alkaline 

 medium ; the pineapple ferment on the other hand acts most ener- 

 getically in a neutral solution, although the ferment is decidedly 

 active in the presence of both acids and alkali carbonate. 



In studying the effect of changes in the reaction of pineapple 

 juice on its proteolytic power, or in measuring. the proteolytic action 

 of the ferment under varying conditions, the following method was, 

 as a rule, made use of ; a given volume of filtered pineapple juice, 

 usually 100 c. c, was warmed at 40° C. for a given length of time 

 with 10 grams of moist, freshly coagulated egg-albumin, which had 

 been completely freed from all soluble matter by thorough washing 

 with hot water. When the period of digestion was completed the 

 undissolved matter was collected on a weighed filter, washed with 

 water until all soluble bodies were removed and then dried at 110° C. 

 until of constant weight. By subtracting the weight of the insolu- 

 ble residue so obtained from the weight of dry albuminj equivalent 

 to the moist albumin used in the experiment, the amount of proteid 

 matter digested, or rather converted into soluble products, was ascer 

 tained. Obviously, however, the so-called undissolved portion of 



* Studies from the Laboratory of Phj-siological Chem., Yale Uuiversity, vol. i, p. 135. 

 f Martin, Journal of Physiology, vol. v, p. 221 ; vol. vi, p. 336. 



\ Determined by simply drying 1 grams of the sampled coagulated albumin at 11 0° C 

 until of constant weight. 



