46 PRESIDENT’S ADDRESS. 
yeasts, beverages possessing the nutritious properties of 
beer wort, with characters similar to wine, can be obtained. 
The modern brewer uses pure cultivations of yeast, so as 
to avoid the formation of undesirable products, and to 
always ensure the production of beers of uniform quality, 
taste, and odour. 
Another example of valuable chemical processes brought 
about by low organisms is Wehmer’s discovery that the 
mould Citromyces will convert sugar to the extent of 50 
per cent. of its weight into citric acid. 
It might be said that these questions are not chemical 
ones, but after all the products are truly and undoubted 
chemical ones, though vital processes have been more or 
less intimately connected in their formation. 
A change appears to be coming over the views held in 
regard to fermentation. The production of alcohol by the 
yeast plant has been generally regarded, since the Liebig- 
Pasteur controversy, as due to the vital processes of the 
yeast plant, but recently it has been stated (by Buchner) to 
be probably of a secondary nature, and to be due to the 
excretion of a ferment by the yeast organisms, which can be 
separated by means of great pressure ; this extract from 
the yeast, termed zymase (an enzyme), like the living yeast 
organisms, is said to cause the fermentation of sugar. This, 
however, requires confirmation ; it is undoubtedly well worth 
further investigation. 
Wroblewski clams that he has isolated the active portion 
of diastase (the greater part was found to be a carbohydrate 
which yielded arabinose when boiled with acids), and found 
that it has the properties of a proteid body. Although it 
has for some time been regarded as a proteid, this is the 
first experimental proof of its being one. 
It appears to be now more or less well established that 
the formation of soil from rocks of various kinds is not 
entirely due to the action of frost, water, carbon dioxide, 
and the accumulation of dead organic matter; but that the 
