493 
Enzyme of Yeast. 
yeast with kieselguhr till the resulting powder was of the 
consistency of flour. This was then ground in an agate 
mill, procured recently from Lautenschlager of Berlin, which 
is used in the Pathological Laboratory here for grinding 
Bacilli. The mill is driven by water-power, and is capable 
of disintegrating the Bacillus of diphtheria. 
This new apparatus materially shortened the operation of 
grinding, so that I was able to carry out the whole operation, 
from the collection of the yeast to the disintegration of the 
cells, in a few hours. I lay considerable stress upon this, 
for reasons which will appear later. 
The absence of any enzyme in the resting yeast made 
it probable that, if present in the cells during active fermen- 
tation, it would not be very stable in the extract. In his 
publications Buchner has pointed out that this instability 
is one of the features of the enzyme as he prepared it. He 
speaks of it as being decomposed after exposure to the 
laboratory temperature for 24 hours, though he found it 
capable of greater resistance if kept at o° C. He says, 
however, that he has kept it for a week without damage 
if it has been in contact with sugar. In order therefore to 
avoid every possibility of losing the enzyme, in case only 
a little should be present in the yeast under experiment, 
I took the precaution of extracting the ground mass, now 
a fine dry powder, with 100 cc. of a 10 per cent, solution of 
cane-sugar. During the progress of the grinding I examined 
every charge of the mill microscopically at intervals, and 
continued grinding until no intact yeast-cells were visible. 
It is of course unlikely that all were disintegrated, but 
certainly not more than 10 per cent, escaped intact. 
On mixing the ground powder with the sugar-solution, 
and stirring it into a thin paste, I was struck by the fact 
that within five minutes an evolution of bubbles of gas took 
place in the paste, much after the manner in which yeast 
causes the fermentation in dough to occur. The bubbles 
rose slowly but constantly all over the surface of the paste. 
I rapidly mixed some unground yeast with kieselguhr, and 
