220 
Brown.— Some Studies on Yeast . 
its own weight of maltose, and also the potential rise of temperature of the 
cell per hour, if all the heat due to metabolism had been retained. 
The values are not strictly comparable, owing to the fermentations 
having been made at different times, and in some cases with different 
yeasts. It will be noticed that between about 14 0 and 16 0 C. the time 
required for a yeast- cell to ferment its own weight of sugar varies from 
about 8^ to 9^ hours, and that the heat generated during one hour is sufficient 
to raise the temperature of the cell by 15 0 or 16 0 C. 
Table I. 
a. 
h. 
c. 
d. 
Maltose fermented 
Time required by 
Potential rise of 
T ean temperature per 100 c.c. per hour , yeast- cell to ferment 
temperature of 
of hxpt. 
per one gramme of 
its own weight 
yeast-cell in one 
yeast. 
of maltose. 
, Me 
hour . — • 
grm . 
Hours. 
s 
(1) 14-3° C. . 
. 0*104 
9-6 
15*1° C. 
( 2 ) 15 * 1 ° • 
0*101 
9-9 
14-6° 
( 3 ) I 5-9 
. 0-105 
9*5 
I5 ’ 2 o 
( 4 ) i6-i° . 
. 0115 
8-7 . 
16-7° 
(5) 16-3° 
. 0-123 
8-i 
17-8° 
(6) 17 - 4 ° • 
0-119 
8-4 . 
. 17-2° 
( 7 ) 17 9 ° 
• 0-133 
7*5 
19 - 3 ° 
(8) 18-3° . 
• 0-134 
7-4 
19-4° 
(9) 19-1° 
. 0-130 
7-6 
18-8° 
(10) 20’9° 
. 0-178 
5-6 
• 25.8 s 
Although the entire range of temperature in these experiments is only 
about 6° C., the influence of increasing temperature on cell-metabolism is 
consistently shown throughout, and the results are such as to indicate a high 
‘ temperature coefficient ’ for yeast. 
During the course of his studies on alcoholic fermentation, A. Slator 
has introduced a new experimental method which in his hands has given, 
and is still giving, results of the greatest possible interest as regards the 
mechanics of fermentation (Journ. Chem. Soc., Trans., 1906, p. 128 ; ibid., 
1908, p. 217). It consists essentially of measuring the fermentative change 
over a brief interval of time by change of manometric pressure due to the 
evolution of C 0 2 . By making the time intervals very short, various dis- 
turbing causes, such as changes of concentration, alteration in the activity or 
amount of the yeast, and the accumulation of the products, are reduced to 
a minimum. 
Slator was thus able to prove satisfactorily that, other things being the 
same, the rate of fermentation of a sugar is proportional to the number of 
active cells in a given volume, i. e. to the £ density of the population ’ ; and 
that the rate is almost independent of the concentration of the sugar except 
in very dilute solutions. 
With this same apparatus, Slator also investigated the influence of 
temperature on the rate of fermentation, and for the first time obtained 
