R. H. Chittenden — Ferments of Pineapple Juice. 291 



Experiment VII. — Aqueous solution of the above described alco- 

 holic precipitate. The 10 grams of moist albumin coagulum used in 

 the digestions contained 1-4138 grams of dry albumin. The mix- 

 tures were warmed at 40° C. for 4 hours. 



Undissolved Per cent. 



Ferment solution. Reaction. albumin. digested. 



A 100" + 100"='^ H.,0 neutral 1-0881 gi-ams 23-1 



B 100 +100 0-2r^HCl 0-lj^HCl 1-4099 0-3 , 



Thus, with this very impure preparation of the ferment the pres- 

 ence of 0-1 per cent, hydrochloric acid was sufficient to entirely 

 prevent any digestive action whatever. Doubtless, even smaller 

 amounts of acid would have the same influence on the more per- 

 fectly isolated ferment. 



As already stated, saturation of pineapple juice, either neutralized 

 or of natural acidity, with ammonium sulphate precipitates all or 

 nearly all of the proteids present in the fluid, the precipitate show- 

 ing by its proteolytic action that it contains the ferment as well. 

 An aqueous solution of such a pi'ecipitate, dialyzed to free it from 

 ammonium sulphate, has a marked digestive action, but when mixed 

 with hydrochloric acid its proteolytic power, like that of the alcohol 

 precipitate, is immediately checked. 



Experiment YIII. — Aqueous, dialyzed solution of the above 

 described ammonium sulphate precipitate. The amount of dry 

 albumin equivalent to the 10 grams of moist coagulum used in the 

 digestions Avas r5120 grams. The mixtures were warmed at 40° C. 

 for 5 hours. 



Undissolved Per cent. 



Fenuent solution. Reaction. albumin. digested. 



A lOO'^'-flOO''^ H2O neutral 1-1791 grams 23-1 



B 100 +100 0-2 ^HCl O-l.'lIHCl 1-4897 1-5 



As previously stated, pineapple juice, and the isolated ferment as 

 as well, manifests its proteolytic action in an alkaline-reacting fluid, 

 as well as in the presence of an acid or neutral reaction. When, 

 however, the solution becomes strongly alkaline proteolytic action 

 is quickly retarded, the ferment in this respect differing very 

 decidedly from the related ferments papain and trypsin. Thus, the 

 addition of small quantities of sodium carbonate to neutralized pine- 

 apple juice, a few hundredths of one per cent., produces no notice- 

 able effect, but as the quantity is increased the retarding action of 

 the alkali becomes more pronounced, tintil at last it checks the pro- 

 teolytic action of the ferment altogether. This is clearly shown in 

 the following experiments: 



Trans. Conn. Acad,. Vol. VIII. 39 Jan., 1892. 



