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



the sodium chloride saturation produces a flock}^ precipitate, sub- 

 stantiating this view. 



Saturation of the neutralized juice with magnesium sulphate like- 

 wise produces a precipitate of proteid raattei", somewhat heavier 

 than that induced by saturation with sodium chloride. Addition 

 of crystals of sodium sulphate to the filtrate from the above precip- 

 itates causes finally a slight additional separation of flocculent mat- 

 ter containing a little proteid. 



Both the sodium chloride precipitate and the magnesium sulphate 

 precipitate are strongly proteolytic. 



The general character of these precipitates will be discussed more 

 in detail later on, in connection with the isolation of the proteolytic 

 ferment. 



Proteolytic action of fresh pineapple juice under varying conditions. 



As already stated, fresh pineapple juice is strongly proteolytic, 

 and its proteid-digesting power is manifested in a neutral, acid, or 

 even alkaline-reacting fluid. In this respect, therefore, the ferment 

 resembles trypsin rather than pepsin. 



When blood fibrin is warmed at 40° C, or thereabout, with filtered 

 pineapple juice of average acidity the fibrin swells up somewhat in 

 the acid fluid, then quickly becomes disintegrated and in part dis- 

 solved, the initial action certainly being as vigorous as that of a 

 moderately strong solution of pepsin-hydrochloric acid. There in- 

 variably remains, however, even after long-continued warming at 

 40° C, a fairly large insoluble residue, not of unaltered fibrin, but 

 of finely divided antialbumid-like matter more or less soluble in 

 weak alkaline fluids, from which it is reprecipitated by the addition 

 of dilute acid. 



Pineapple juice neutralized, or made very faintly alkaline, with 

 dilute sodium carbonate acts apparently in much the same manner 

 as the acid juice, except that in the alkaline-reacting fluid there is 

 less residue of antialbumid-like matter and in the neutralized juice, 

 naturally, an utter absence of any swelling of the fibrin. An ex- 

 amination of the several digestive mixtures, however, shows that the 

 products formed in a neutral or alkaline solution are different some- 

 what from those formed in an acid-reacting fluid, a point which will 

 be referred to again later on. 



One of the most noticeable features in the digestive action of the 

 pineapple ferment is its peculiar softening and disintegration of the 

 proteid matter. This is most noticeable in a neutral solution; thus 



