PROTEASES 361 



To isolate the enzymes from the fluid contained within 

 the pitchers of Nepenthes, Vines * added to the liquid an equal 

 volume of absolute alcohol, then phosphoric acid followed by 

 lime water in order to increase the bulk of the precipitate. 

 Ammonium carbonate was added until the liquid gave a 

 neutral reaction, and the precipitate filtered off. For use, 

 the precipitate was shaken up with a '2 per cent solution of 

 hydrochloric acid and filtered ; the clear filtrate actively digests 

 fibrin. 



If it be desired to examine the contents of a tissue for 

 these ferments, the expressed juice may be used, or an aqueous 

 extract, the enzyme being separated as above if necessary. 

 But sometimes this is unsatisfactory for various reasons — a 

 syrup-like consistency or high coloration, for example. In 

 such cases the tissues may be bruised in a mortar and placed 

 with water in the vessel in which the experiment is to be 

 carried out, together with the material — fibrin, for example — 

 to be acted upon.f Buscalioni and Fermi \ used sterilized 

 gelatine, with '5-1 per cent carbolic acid as an antiseptic, in a 

 Petri dish. P'ragments of the tissue to be tested are placed 

 upon the jelly ; the liquefaction of the gelatine in the neigh- 

 bourhood of the pieces indicates the presence of proteolytic 

 enzymes, but inasmuch as all proteases do not attack gelatine, 

 a negative result does not necessarily indicate the absence of 

 these enzymes. 



Dean § prepared ereptase from the seeds of beans by ex- 

 tracting the cotyledons with water, filtering, and half saturating 

 the filtrate with ammonium sulphate. The precipitate thus 

 obtained is filtered off, dissolved in water and separated from 

 ammonium sulphate by dialysis. The solution of enzyme thus 

 purified may be dried at a temperature below 50° C. 



Vines 1 1 separated peptase from ereptase by making use of 

 the fact that the former is hardly soluble in water but readily 

 so in a dilute solution of sodium chloride, whilst ereptase is 

 easily soluble in water. The material, e.g., seed of Cannalns 

 sativa, is ground and extracted with a 10 per cent solution of 



* Vines: "Ann. Bot.," 1897, 11, 573. 



t Vines: id., 1903, 17, 237, 597. 



J Buscalioni and Fermi : "Ann. R. Inst. Bot., Roma," 1898, 7, 99. 



§Dean : " Bot. Gaz.," 1905, 39, 321. 



1 1 Vines: "Ann. Bot.," 1908, 22, 103, 



