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PRODUCTION OF MILK OF LOW BACTERIAL CONTENT. 45 
evidence of great contamination, is evidently not due in most cases to 
original contamination. The results show that extremely high counts 
in milk are in general the result of bacterial growth rather than 
original contamination. 
THE EFFECT OF TEMPERATURE ON THE GROWTH OF BACTERIA 
IN MILK. 
The results shown in the previous discussion of the factors essen- 
tial for the production of milk of low bacterial count when fresh 
apply only to fresh milk. The dairyman must remember that when 
milk of that kind has been produced his responsibility has not ended, 
for the milk must be kept cold to prevent the growth of bacteria. 
The three factors discussed prevent to a large degree the contamina- 
tion of milk during production, as the term is used in this bulletin. | 
In the broad sense of the term “ production of milk,” the effect of 
temperature at which the milk is held on the farm must also be con- 
sidered. It is one of the greatest problems in the handling of milk 
on the farm, and extensive studies have been made to show the effect 
of holding milk at different temperatures-during varying lengths of 
time. Samples of milk produced under different conditions were 
held at 4.4°, 10°, and 15.5° C. (40°, 50°, and 60° F.) and examined 
when fresh and after each interval-of 24 hours for 96 hours, or 4 
days. The milk was produced in the experimental barn under three 
different sets of conditions, as follows: 
First. Cows were clean and bedded; the udders washed part of the 
time and left unwashed part of the time; the small-top pail’ used; 
and all utensils were sterilized. 
Second. Cows were dirty; the manure was removed twice a week; 
both open and small-top pails used; and all utensils were sterilized. 
Third. Conditions same as second except that the utensils were not 
sterilized. 
Complete detailed results showing the growth of the bacteria in 
the milk produced under the different conditions mentioned are given. 
Twenty samples produced under condition 1 were studied ; 34 samples 
under condition 2, and 30 under condition 3. 
The bacterial development in milk having a low count, as described 
under the first condition, is shown in Table 20. The calculated ratio 
of the bacterial growth in each sample is shown in Table 21. The 
~ bacterial development in milk under the second condition mentioned 
is shown in Table 22 and the ratio of the bacterial development in 
Table 23. Tables 24 and 25 show similar results for milk produced 
under the third condition. The summary of the averages of all the 
samples studied during this work is shown in Table 26. It will be 
noted that the milk produced under the three conditions when fresh 
showed somewhat different bacterial counts; that produced under 
condition 1 averaged 4,295 bacteria per cubic centimeter; under con- 
dition 2, 39,082; and under condition 3, 136,533. It will be seen, 
