Green.— On Vegetable Ferments. 125 
support of the hypothesis of their proteid nature we have the 
fact that when an extract containing an enzyme has all its 
proteids removed by precipitation, the filtrate possesses little 
or no ferment power, the latter being diminished in many 
cases in proportion as the proteid is thrown out of solution. 
This may, however, only indicate that the ferment is precipi- 
tated with the proteid, and indeed it is known that quite inert 
precipitates can carry enzymes out of solution with them, a 
fact taken advantage of by Briicke in his process for preparing 
pepsin. A more striking fact is that the temperatures at 
which so many enzymes are destroyed correspond very 
closely to the points at which proteids occurring with them 
are coagulated. Chittenden calls attention to this point in 
his work on the pine-apple 1 , and it has been noticed by 
many writers on the animal ferments. 
On the other hand, we have considerable evidence to show 
that though associated with proteids in the cells, there is no 
identity between them and the latter. Hartley has shown 
that at least some of them do not act upon the spectrum in 
the same way as proteids do ; chemical analysis too shows 
them to contain less nitrogen than the latter bodies. Too 
much stress should perhaps not be laid upon this fact, as we 
have no evidence that the bodies analysed were the pure 
enzymes. Evidence against their being proteids can be de- 
duced from the modes of preparation which in some cases 
have been found to yield them in very active condition, and 
which present them in solutions giving very slight, if any, 
proteid reactions. Briicke’s method of preparing pepsin from 
the stomach shows clearly that this at least is not a proteid. 
We must admit, however, that they are in some way very 
closely attached to such bodies, particularly to certain mem- 
bers of the globulin-group. 
In recent years one ferment has been the subject of critical 
examination. O’Sullivan and Tompson, in their paper already 
quoted, have published an account of a long series of experi- 
ments that they carried out with a view to ascertaining the 
1 op. cit. 
