I IO 
Green.— On Vegetable Ferments. 
The acidity of the natural juice is equal to about an acidity 
of *5 per cent. HC1 ; the proteolytic powers in such a juice 
compared with those in a neutralised one being about as 3 : 4. 
Alkalinity is also harmful, -5 per cent. Na 2 C 0 3 hindering the 
decomposition of the proteid, and 1 per cent, inhibiting it 
altogether. The ferment, if freed from the salts, &c. present 
in the natural juice, by precipitation by alcohol and subse- 
quent solution in water, is still more sensitive to acid, being 
quite without effect in the presence of *1 per cent. HC1. 
The temperature at which it has the greatest activity also 
varies with the reaction. The natural juice works best at 
40° C., and is stopped and the ferment destroyed at 70°, 
The ferment in the neutralised juice continues active at this 
temperature, and is not destroyed under 8o° C., its optimum 
being between 50° and 6o° C. 
The ferment can be separated from the juice by several 
methods, but none yield it pure, the proteids of the juice 
being thrown down with it. It can best be precipitated by 
saturating the juice with NaCl or MgS 0 4 : less advantageously 
by saturation with sulphate of ammonium, or by about 80 per 
cent, of alcohol. 
The part that these four proteohydrolytic enzymes play in 
the metabolism of the plants in which they occur is not very 
evident. The probability that such bodies have a good deal 
to do with the processes of germination soon occupied the 
minds of botanists, and such seeds as store quantities of 
reserve proteids in their tissues were the subjects of research 
for some years after the discovery that the ferments existed. 
In 1874, von Gorup-Besanez 1 detected an enzyme in the seeds 
of the Vetch, which has the power of forming peptone from 
fibrin, and in 1875 he made known the existence of the same 
body in the seeds of Hemp, Flax, and Barley 2 . He did not 
indicate, however, what its action is on the reserve proteids of 
the seeds. In 1878 Krauch 3 criticised adversely his methods 
1 Ber. d. deutsch. Chem. Gesells. 1874, p. 1478. 2 Ibid. 1875. 
3 Beitrage zur Kenntniss der ungeformten Fermente in den Pflanzen, Berlin, 
1878. 
