KFFECT OF TEMPERATURE ON BACTERIA. 45 
2. In this milk nearly every species present in the original 
milk developed and was present at the close, each showing 
quite a high percentage, even at the end of the experiment. 
Group V. disappears entirely, and Group II. apparently so. All 
the others are present in almost as large percentage at the end 
as at the start. 
3. The chief development of bacteria in this sample was due 
to Group [V., the neutral’ bacteria, which increased in numbers 
to 328,000,000 per cubic centimeter, after which there was a 
slight decline. Group I., the normal acid bacteria, also devel- 
oped abundantly; but the increase in numbers of this group did 
not begin until about 4 days after the beginning of the ex- 
periments. After this there was a regular increase up to 
96,000,000, constituting about 24 per cent.” 
4. . The development of the liquefying bacteria was especially 
striking. They increased with more or less constancy through 
the whole experiment, and toward the end comprised about a 
quarter of all the bacteria present. In the last experiment there 
was a Slight decline in numbers. 
Milk kept at 20°.—1. At 20° avery different result is seen. 
The bacteria began to grow rapidly just before the 12th hour, 
and the chief growth from this time on was due to the lactic 
bacteria—Groups I. and II.—which in the end comprised over 
99 per cent. of all species. 
2. The liquefying bacteria in this case were rapidly ex- 
cluded from the milk, and were not found in the experiment 
after 36 hours. 
32) Group ise, B. aerogenes, developed slightly, but even 
at the end only composed o.3 per cent. of all the bacteria. 
Milk kept at 37°.—1. At 37° the results were in some re- 
spects similar to those at 70°, for here also the two groups, I. 
and II., comprised at the end a large majority of the bacteria 
—about 96 percent. There was, however, at this temperature 
a larger per cent. of Group III., namely, 3 per cent., or about 
11,000,000 per cubic centimeter. 
2. It will be noticed also that the liquefiers remained in 
considerable numbers to the end of this experiment, not being 
wholly excluded as they were at 20°. The neutral group, IV., 
