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PRESIDENT S ADDRESS. 
which on splitting up produces prussic acid in addition 
to glucose, and may consequently be termed a cyanogenetic 
glucoside. Bach glucoside which occurs in nature is accom- 
panied, at any rate at some stage of its existence, by a special 
enzyme which can hydrolise it or split it up by the help of 
the elements of water. Glucosides would appear to act as 
reserve material for the plant in emergencies or at critical 
periods of its de\ elopment, their constituents being capable of 
assimilation only after contact with the enzyme and hydrolysis 
by it. 
Returning now to linseed, our next step is to attempt to 
isolate (1) the glucoside and (2) the enzyme. To isolate the 
glucoside, the thoroughly dried and powdered material is 
extracted with alcohol, and the partially-evaporated alcoholic 
extract poured into water to precipitate the oily and resinous 
matter and the chlorophyll. The decolorised and filtered 
aqueous liquid is now evaporated to a syrup, which is very 
rich in glucoside, and from this syrup by appropriate and 
patient methods the glucoside can be induced to crystallise 
in masses of rosettes of slender needles. 
It next remains to separate the enzyme, and this can be 
done by extracting the finely-ground and dried linseed with 
water, previously saturated with chloroform as an antiseptic. 
On pouring this liquid, which contains the enzyme in 
solution, into an excess of alcohol, a white precipitate of 
amorphous proteid matter is thrown down. This when dried 
by exposure to air is the purest form of enzyme obtainable 
in the active state. 
On adding a little of this enzyme extract to the gluco- 
side crystals dissolved in water, hydrolysis take place, the 
glucoside disappears as such, and hydrocyanic acid, acetone, 
and sugar are produced, just as in the macerated plant 
tissues. But, however much glucoside be decomposed , the 
enzyme remains unaltered and can be recovered as such from 
the mixture after the reaction is finished. The same can be 
