in the frtdt of Cucumis utilissimus , Roxb. 201 
sufficient quantity to give a good biuret reaction. After 2 
days the experiment was stopped, and the dialysates com- 
pared. That of the control H gave no evidence of peptone by 
the biuret test. Both were then evaporated to dryness over a 
water bath. The residue from the dialysate of G was much 
the more copious of the two. 
These residues were dissolved in a small quantity of distilled 
water, and precipitated by neutral acetate of lead, a reagent 
which throws down peptones, and forms an insoluble com- 
pound with leucin, an amide body which occurs in the pro- 
found decomposition of proteids brought about by tryptic 
ferments. The appearance of leucin in the dialysate would 
afford evidence that the ferment under examination is a 
trypsin and not a vegetable pepsin. 
Comparing the two after addition of the acetate of lead it 
was found that there was a precipitate in both, but much the 
greater quantity in G. After well washing, these precipitates 
were suspended in water, and a stream of H 2 S passed 
through, till the liquid was saturated with gas and all the 
lead thrown down as Pb. S. Most of such peptone as 
was present in G was by this treatment rendered insoluble 
and was removed by filtration with the lead sulphide. The 
filtrate, containing now any leucin that might have been 
present, and any diffusible bodies that, being present in the 
original extract, behaved with regard to lead acetate in the 
same way as leucin, was concentrated to a very small bulk, and 
treated with boiling alcohol, in which leucin is soluble. After 
filtering, this alcoholic extract was in turn concentrated, 
and allowed to deposit the crystalline matter which it 
contained. Both dialysates, treated thus, threw down crystals, 
G depositing the greater amount. The crystals from G were 
found to be of two kinds : one, not very plentiful, separating 
in rosettes, which were doubly refractive ; the others, in 
much greater quantity, had not a very definite crystalline 
form, and were only very feebly, if at all, doubly refractive. 
H contained only the rosettes. The crystals were then puri- 
fied by repeated crystallisation from water, till they were 
