46 
MR, J. R. GREER OR THE CHARGES IR THE PROTEIDS 
The subsequent or coincident appearance of peptone and crystalline bodies has 
already been described. For the satisfactory demonstration of the formation of these, 
an experiment was made on a large quantity of fibrin which was subjected for a week 
to the action of 25 c.c. of the extract. At the conclusion of this time the method 
used to separate leucin by v. Gorup-Besanez in his investigations was followed. 
The liquid was boiled, filtered, and neutralised ; the neutralisation precipitate removed, 
and acetate of lead added. This body forms a compound with leucin which is 
insoluble in alkaline fluids. The precipitate so formed was filtered off, and suspended 
in water. The leucin and lead compound was then decomposed by passing a stream 
of SHo through it, and the sulphide of lead so formed removed by filtration. The 
filtrate was evaporated to dryness and extracted with boiling absolute alcohol. The 
last reagent would take up leucin, but not any traces of proteids that had gone 
down with it. The alcohol extract was then evaporated to concentration, when it 
deposited the crystals. The essential nature of the action of the extract on fibrin 
having thus been established, it becomes possible to speak of the presence in it of a 
proteolytic ferment and to consider this a tryptic rather than a peptic one. 
Several points connected with its action were then investigated. 
1. At what temperature is it most active ? 
The influence of temperature on the ferments of the animal organism is one of the 
most remarkable features they possess. Their action is suspended at a very low 
degree, gradually improves up to an optimum, which is the temperature of the animal 
body, and beyond this point declines, till on exposure to about 70' C. they are 
destroyed. 
It does not seem improbable that, as the proteolytic ferment of the Lupin works 
naturally in a body which is not at so high a temperature as that occurring in the 
alimentary canal, a lower degree of heat than that would suit it best. In the experi¬ 
ments on the point 20 c.c. of the dialysed glycerine extract were taken and diluted 
with 20 c.c. of HC1 of '4 per cent, strength. This was then divided into two, and a 
measured quantity of boiled swollen fibrin was placed in each. One was kept at the 
temperature of the laboratory, and the other put in a water-bath at a temperature of 
37° C. After two days’ digestion three-quarters of the fibrin in the latter had been 
digested ; the liquid was turbid, and peptone in abundance present. In the former, 
digestion was just beginning to be evident, the edges of the fibrin only being corroded 
away. Two days later the warm tube contained no recognisable fibrin, while the cool 
one showed digestion about half completed. 
Boiling the fluid which contained the ferment effectually destroyed its activity. 
It therefore corresponds in its behaviour to the animal ferments, working best at a 
moderately high temperature, such as 40° C., but being destroyed by too great heat. 
