48 STORRS AGRICULTURAL EXPERIMENT STATION. 
the amount of acid is just as likely to be greater in the strained 
sample kept at 70° as in the unstrained sample. In short, 
straining has no effect upon the development of acid. 
4. The effect of straining upon the development of acid bac- 
teria.—The total number of acid bacteria was practically the 
same in the strained and unstrained samples after they had re- 
mained at 70° for 50 hours. The averages were 453,000,000 
in the unstrained and 495,000,000 in the strained samples, the 
difference between the two numbers not being sufficient to have 
any significance. 
6. The relation of the production of acid to the development of 
acid bacteria.—In these tables it will be seen that in general 
the milk samples with the highest per cents. of acid show a 
larger number of acid bacteria than do those with a smaller 
per cent. of acid. 
MILK KEPT FOR 50 HOURS AT 50. 
1. Zotal numbers.—A most striking effect seen in these 
tables is the result of the temperature of 50° upon the total 
number of bacteria. It was to be expected that the number 
would be somewhat smaller than at 70°, but the difference is 
larger than would be supposed. The average number of bac- 
teria in these samples at the end of 50 hours was 6,000,000. 
The average number in the samples kept at 70° was very nearly 
500,000,000. , 
2. Lhe effect of 50° upon growth of actd bacteria.—The effect 
of the lower temperature in reducing the development of the 
acid bacteria was even greater than its effect in reducing the 
total number. Not only was the number of acid bacteria very 
much less in these samples than in the samples at 70°, but 
the percentage of acid bacteria was decidedly less. The 
average percentage of acid bacteria in the samples kept at 
70° was, as we have seen, nearly 99; the average percentage 
of acid bacteria in the samples kept at 50° for 50 hours was 
about 66. This interesting fact is what might be expected 
from results previously published. ‘The great development of 
bacteria in milk after 24 hours is, as we have shown elsewhere, 
due chiefly to the development of lactic organisms. The lower — 
temperatures, which check the development of bacteria, have 


