H. a. Chittenden — Ferments of Pineapple Juice. 285 



cipitate remains clear even when the solution is boiled, but a drop 

 or two of acetic acid added to the hot fluid produces a turbidity, 

 which on further heating eventually changes to a flocculent precip- 

 itate. In the filtrate from this second precipitate, acetic acid and 

 potassium ferrocyanide show the presence, in small quantity, of 

 what is presumably a non-coagulable proteose. It is thus evident 

 that the presence of acid lowers the temperature at which these 

 bodies are precipitated by heat, and further that the substance pre- 

 cipitated at 10U° C. can be made to separate only in the presence of 

 dilute acid. This fact certainly favors the view that the juice 

 contains two distinct proteids precipitable by heat, the one at 

 about 75° C. in an acid solution or 82° C. in a neutral fluid, the 

 other at 100° C. in an acid fluid. On the other hand, the above 

 reactions might be produced by a single substance slowly or incom- 

 pletely precipitated by heat, analogous to the separation of Mar- 

 tin's* /i' phytalbumose, which is described as separating in two dis- 

 tinct stages, viz: at from 78**-82° C, and from 83°-95° C. As 

 against this latter view, however, we have the apparent fact that 

 in the pineapple juice, one of the proteids is precipitated from a 

 neutral or acid fluid by heat, the other only from an acid fluid. 



Long continued dialysis (10-12 days) of neutralized pineapple 

 juice in running water, protected from putrefaction by addition of 

 thymol, gives little or no separation of any proteid matter. A faint 

 turbidity may appear, but no separation suflficiently large to collect 

 on a filter. Such turbidity as does piake its appearance clears up on 

 the addition of a few drops of a strong solution of sodium chloride, 

 or of dilute nitric acid ; two reactions equally characteristic of a 

 globulin or of heteroproteose. 



Saturation of neutralized, or acid, pineapple juice with pure am- 

 monium sulphate precipitates all of the proteids present in the fluid, 

 together with a small amount of non-albuminous matter. In this 

 precipitate are contained both the proteolytic and rennet-like fer- 

 ments. 



Saturation of neutralized pineapple juice with sodium chloride 

 gives rise to a small flocculent precipitate of proteid matter, which 

 is not at all increased by the addition of acetic acid to the salt- 

 saturated fluid. Addition of ammonium sulphate in substance to 

 the filtrate from the salt-saturation precipitate produces a further 

 precipitate of proteid matter, thus suggesting a possible separation 

 of two distinct bodies. Further, simple boiling of the filtrate from 



* Journal of Physiology, vol. vi, p. 34.9. 



