292 
president’s address. 
genesis in linseed, and an explanation of the conditions 
under which it occurs will serve as a particular case to 
typify the properties and mode of action of enzymes in 
general. I can only touch the fringe of the subject. It is a 
vast one, for “life is a series of fermentations,” and to probe 
beneath the surface in this region is to reveal unplumbed 
depths in bio-chemistry and bio-physics, depths which some- 
where reach the very citadel of vital phenomena. When 
linseed (ground seed of flax, Linum usitatissinum) is macerated 
with warm water and allowed to stand for some time, the 
development of hydrocyanic or prussic acid gradually takes 
place. This is shown by the characteristic odour of the acid, 
and by distilling off the volatile acid and subjecting it to its 
specific tests. Flax seed exhibits this property faintly, but 
young flax plants show it much more strongly. If an anti- 
septic such as chloroform or toluene be added to the mash 
of linseed and water, prussic acid is still found. If the 
linseed is placed in boiling water, no prussic acid is evident 
in the mash. It is clear, therefore, that the prussic acid 
does not exist as such in the linseed, but is produced by 
some reaction or process which is inhibited at the tempera- 
ture of boiling water, but is not inhibited by an antiseptic. 
It cannot, therefore, be due to micro-organisms. Now on 
heating the mash made with boiling water, hitherto free 
from prussic ’acid, with dilute hydrochloric acid, prussic acid 
is at once produced together with sugar and acetone. And 
on examining the mash made with warm water only, we also 
find sugar and acetone as well as prussic acid. It is clear, 
therefore, that the production of these substances is due to 
the interaction of at least two bodies present in linseed 
tissues, one not destroyed at the temperature of boiling 
water, the other destroyed. Moreover, the latter has the 
same action as hydrochloric acid has upon the former. This 
suggests an analogy with what occurs in the seeds of the 
bitter almond ( amygdalus communis), which as long ago as 
