582 Vines . — The Proteolytic Enzyme of Nepenthes. 
ment with regard to the enzyme of Nepenthes 1 : but he did 
not specially investigate the products of digestion. With regard 
to papain, which is, however, an altogether tryptic enzyme, 
active in neutral or alkaline liquids, Martin states that it pro- 
duces peptone, leucin and ty rosin from fibrin 1 2 , though it does not 
produce true peptone from vegetable proteids 3 , but a ‘ peptone- 
like body 5 which splits up into leucin and tyrosin. Finally, 
Green 4 has found that the proteolytic enzyme in the germina- 
ting seeds of Lupinus hirsutus produces, both from fibrin and 
vegetable proteids, a ‘ so-called peptone/ leucin, and tyrosin ; 
and though it is only active in an acid medium, he regards 
the enzyme as ‘ tryptic rather than peptic.’ The assertion 
that peptone is a product of the activity of these enzymes 
is based, by von Gorup-Besanez, on the reactions already 
enumerated (p. 578) ; and by Martin and Green mainly on the 
results of dialysis. It must, however, be pointed out that 
neither the reactions nor the dialysis are absolutely conclusive 
on the point. The only certain proof that a liquid contains 
true peptones lies in the fact that such a liquid continues 
to give proteid reactions after saturation with ammonium 
sulphate, since this neutral salt precipitates all proteids except 
true peptones : but this test was not applied in any of the 
above-mentioned researches. As I have already pointed out, 
I have invariably found that a solution of the products of 
digestion by pitcher-liquid gives no proteid reactions after 
saturation with ammonium sulphate, all the proteids present 
having been precipitated by the salt. I conclude, therefore, 
that true peptone is not one of the products of digestion. 
The proteid product of digestion appears to be deutero- 
albumose. It is, however, possible that true peptone may be 
formed, and be immediately split up into leucin or bodies 
of that kind. Otherwise it must be assumed that the albu- 
moses formed in digestion are directly split up into these 
bodies, a view which gains some support from the fact that 
1 Von Gorup-Besanez, Sitzber. d. phys.-med. Soc. zu Erlangen, 1876. 
2 Journal of Physiology, V, 1884. 3 Ibid. VI, 1885. 
4 Phil. Trans. Roy. Soc., vol. 178, B, 1887. 
