34 
F. F. Blackman. 
the general control of the cell. The enzymes we have overcome 
without a very strenuous struggle, and, isolated one by one with the 
progress of knowledge, most of them can now be preserved and 
at any time can be made to exhibit their respective fermentations 
under conditions (as regard temperature, concentration and presence 
of the products of their activity) quite comparable with those 
holding within the living cell. 
The “ alcoholic ” fermentation process, in which sugar is split 
up with the production of alcohol and C0 2 , remained for a long 
time apart, until in 1896 the researches of Buchner showed that it 
could be carried on abundantly, in a test tube, with the juice 
expressed from yeast cells disintegrated by grinding with a sharp 
powder, while kept very cold throughout. 
The existence of a specific enzyme “ zymase ” that somehow 
is normally destroyed when the whole yeast cell dies, and is under 
any condition not very permanent, was the simplest hypothesis in 
explanation. The researches of Macfadyen in 1900, however, 
make us hesitate before assuming that we have here the action of 
so small a detached fragment of the cell-machinery as an enzyme. 
He points out that this expressed juice uses up more sugar than 
reappears in the form of alcohol and C0 2 , and that this extra amount 
of sugar disappears completely and no trace of it in carbohydrate-form 
can be found, either by hydrolysis or by other means. There is appa¬ 
rently still existing in this expressed juice a sufficiently complex 
part of the cell-protoplasmic machinery to be capable of building 
the sugar irremoveably up into its own substance by anabolic pro¬ 
cess. Now this indicates a very high organisation still undestroyed, 
and possibly sufficient of the chemical manifestations of vital 
protoplasmic activity are present to justify calling this viscous 
juice “ expressed protoplasm,” and its action residual vital activity. 
If so the alcoholic fermentation is possibly due to a portion of this 
machinery of greater complexity than the ordinary enzyme. 
The most ambitious attack that has yet been made upon those 
functions which have been authoritatively held to be the prerogative 
of protoplasm is to be found in the recent work on the question 
whether the photo-synthesis of C0 2 can be carried out inde¬ 
pendently of vitality as a more or less isolated phenomenon in vitro. 
This is a question of the first importance. Should it ever be 
possible to control such a reaction there will open up to the imagi¬ 
nation the prospect, remote enough indeed, of the laboratory com¬ 
peting with the green plant in the direct utilisation of the sun’s 
