553 
Enzyme of Nepenthes (//). 
The clue to the matter was found on this wise. The 
method which I had followed (see my paper of Dec. ’97, 
p. 579) in examining the products of digestion involved the 
precipitation of these substances by filtration into excess of 
alcohol. Whilst investigating the nature of the ultimate 
products, I evaporated a considerable quantity of the alcohol 
which had been used for precipitation, and this left a dark 
brown syrupy residue. Some of this residue, dissolved in 
a small quantity of distilled water, formed a brownish solution, 
giving no precipitate on boiling, but good xanthoproteic and 
biuret reactions. A portion of this solution was put to 
saturate with ammonium sulphate and gave a dense precipitate 
which brought down with it all the colouring-matter ; the 
clear, colourless liquid obtained on filtration still gave strong 
xanthoproteic reaction, and continued to do so after continued 
saturation for two days longer. Another portion of the brown 
solution was put to dialyze, and within twenty-four hours 
the dialysate gave strong xanthoproteic reaction ; on saturat- 
ing the dialysate with ammonium sulphate, there was a 
precipitate, the filtrate from which still gave the xanthoproteic 
reaction, and continued to do so on further saturation. These 
observations indicated the presence of peptone without, how- 
ever, absolutely establishing it ; for it might be the case 
that the precipitation of the deutero-albumose by means of 
ammonium sulphate had been incomplete, and that the proteid 
reactions were due to this substance rather than to peptone. 
It became necessary, therefore, to employ some method 
by which the separation of deutero-albumose and peptone 
could be certainly effected. Fortunately I applied for advice 
to Mr. Ramsden, Fellow of Pembroke College, who has an 
intimate knowledge of the chemistry of proteids, and he 
kindly directed me to a paper by Kuhne 1 on this very point. 
Kiihne’s method consists in saturating the neutralized diges- 
tion-liquid with ammonium sulphate when boiling. After 
1 Zeitschrift fur Biologic, 1892 (Erfahrungen iib. Albumose und Pepton). 
It may be asserted that, until the appearance of this paper, no true peptone 
had been obtained free from albumose. 
P p 2 
