138 
The results of the experiments show that the pure yeast excretes 4 
proteolytic enzyme that is fairly active, and from the fact that it works 
in the presence of neutral and alkaline salts, it must be of a tryptic nature. 
It seems to be of the same nature as the trypsin extracted by Edkins, 
since it works best in the presence of NaCl. 
The experiments on the compressed yeast and the bacteria obtained 
from the compressed yeast show undoubtedly the presence of an enzyme, 
but the indications point more strongly to a bacterial than to a yeast 
origin, since it was not necessary to break the yeast cells before the press- 
ing in obtaining the enzyme, and also, since in experience with pure yeast 
cultures, only three cases have been noted in which any perceptible 
enzymic action took place. Then the bacterial extract was very strong, so 
that though only a comparatively small number of bacteria are present 
in the compressed yeast as compared with the yeast, the activity of the 
extract would be accounted for. Then again though the bacterial and com- 
pressed yeast extracts did not act uniformly, they showed the same pe- 
culiarity in the greater activity of the extract in the presence of Na,CO,. 
Work with a mixture of organisms is always open to the doubt in regard 
to the action of each organism. 
DESCRIPTION OF THE YEAST. 
The cells of this species are very variable in shape, being round, 
elliptic, elongated and irregular, slender at one end and widening out to- 
ward the other, or showing projections from the sides (Ill. 1). These 
irregularities occurring to the greatest extent in wort gelatine cultures 
(Ill. 2). In wort the cells become much elongated and are in long chains 
(Ill. 8), while in lactose solution the round cells predominate and occur 
mostly in pairs. Occasionally giant cells are found in the cultures. The 
cells which are round in a lactose solution, when placed in wort in a moist 
chamber, lengthen inside of twenty-four hours. (Ills. 4, 5.) 
They vary in size, the round cells averaging 3.3 “ in diameter, while the 
average of the elongated are 3.3 ” by 10 u. 
This yeast does not ferment sucrose or lactose. It forms a fairly heavy 
sediment in the sucrose, but only a slight growth in the lactose. In dex- 
trose it required six days for fermentation to start and twenty-four hours 
to form 3 cc. gas. In wort, which contains maltose, fermentation started 
in four days, and 25 ce. of gas were formed in three days, when the cul- 
