Vines.-— Proteolytic Enzyme of Nepenthes (III). 569 
hence Martin was unable to find any crystals of tyrosin 
in his experiments with papain, though he ascertained 
its presence among the products of digestion by Millon’s 
reaction. 
Short of the actual separation of these substances, there is 
no qualitative means of detecting them in the presence of 
peptones and albumoses which, of course, always occur in 
digestion-liquids. I have endeavoured to precipitate these 
proteids by means of absolute alcohol ; but the albumoses or 
peptones formed in nepenthin-digestion are remarkably soluble 
in alcohol, so that when the residue obtained by evaporating 
to dryness a digestion-liquid is extracted with absolute 
alcohol, the solution still gives the biuret reaction, showing 
that albumoses or peptones have been taken up. Tyrosin, it 
is true, gives characteristic colour-reactions : but these are also 
given by peptones and are useless when a mixture has to be 
dealt with. 
If I am not in a position, at present, to establish my 
contention by such direct evidence as to the separation of 
leucin and tyrosin in measurable quantity would afford, I can 
at any rate adduce indirect evidence of a convincing character. 
As long ago as 18 31 , it was observed by Tiedemann and 
Gmelin (10) tha on the addition of chlorine-water to the 
liquid resulting from a pancreatic (tryptic) digestion, after 
acidification, the liquid acquires a colour varying, according 
to its concentration, from pink to violet ; when concentrated, 
there is a violet precipitate. This colouration is due to the 
presence of a substance which, together with leucin, tyrosin, 
and other bodies, is a product of tryptic, as distinguished from 
peptic, proteolysis. The substance in question is a chromogen, 
termed proteinochromogen by Stadelmann (9), but better known 
by the name tryptophan given to it by Neumeister ( 8 ) ; and its 
presence affords a ready means of distinguishing tryptic from 
peptic digestions. 
I have found that the liquid resulting from a somewhat 
prolonged digestion of fibrin by the pitcher-liquid of Nepenthes, 
in the presence of either hydrochloric or citric acid, gives the 
