EFFECT OF TEMPERATURE ON BACTERIA. 37 
APR RIMUN DE NO: 1: “FRBRUARY=:2. 
This experiment was merely a preliminary one, designed to 
give an idea of the numbers of bacteria to be expected and the 
necessary dilution. Only a single plate was made at each test, 
and the results are, therefore, not very trustworthy. But since 
the growth of bacteria agreed in general with that of the later 
and more accurate experiments, the results are given here. 
Milk was obtained at 8 A. M. and divided, as described, into 
thgeesiots; lhe milk kept at»37° curdled in 16 hours; that 
kept at 20° curdled in 40 hours; the sample kept at 12° did not 
curdle in 96 hours, but at the end of the experiment was some- 
what thickened, and had a pleasant butter aroma. ‘Tables 1, 
2, and 3 represent the results of the analyses of the sample at 
different periods. 
In these tables the following chief points are to be noted: 
Milk kept at 12°.—1. ‘The increase in bacteria during the 
experiment was chiefly in Group IV., the group of neutral 
bacteria. ‘The number at the end of 4 days became very high, 
Over I,300,000,000 per cubic centimeter; but in spite of this 
large number the milk was not curdled. 
2. Along with this great development of neutral bacteria 
the lactic bacteria developed appreciably, and there were about 
20,000,000 per cubic centimeter of the first two groups at the 
end of the experiment. 
3. The liquefiers continued to grow through the whole 
period. 
The failure to obtain a proper dilution made the last tests 
unsatisfactory. — 
Milk kept at 20°.—1. A striking contrast is seen between 
this and the 12° milk. The neutral group IV. developed only 
moderately, reaching the number of 97,000,000 in 24 hours, 
after which they slightly declined. 
2. ‘The chief growth of bacteria at this temperature was the 
Group I., that is, B. /actis acidz, and Group II., which may be 
the same species. [hese two comprised over 93 per cent. of 
all bacteria present at the 36th hour. 
3. All others disappeared except a few stragglers of BL. 
aerogenes—Group III.—and a very small number of liquefiers, 
