middle milk taken 
milking which was 
- PRODUCTION OF MILK OF LOW BACTERIAL CONTENT. 25 
During this ex- 
periment the aver- 
age count of the 
directly from the 
udder of two cows 
was 1,172 bacteria 
per cubic centimeter, 
which, subtracted 
bron 2,667, the 
count of the entire 
milked into small- 
top pails, leaves 
1,495, or the number 
of bacteria per cubic 
centimeter intro- 
duced into the small- 
top pail by external 
contamination. 
Similarly the aver- 
age udder count of 
middle milk of the two cows milked into open pails was 1,557, which, 
when subtracted from the average of the open pail, 4,947, gives a 
Fig. 15.—Condition of the flank and udder of one of the 
cows during Experiment No. 7. 
difference of 3,390 bacteria per cubic centimeter to represent the 
number introduced by external contamination. 
In this final experiment we again used a few simple factors, 
namely, sterilized utensils, clean cows with clean udders and teats, 
and the small-top pail. The figures confirm the previous results. 
CONTAMINATION OF MILK BY UNSTERILIZED UTENSILS. 
In this work the results have indicated that generally the greatest 
contamination of milk comes from the use of unsterilized utensils. 
Since that factor is so important in the production of low-count 
milk it deserves special consideration, and therefore additional data 
on the subject are presented. 
Table 9 shows the results of the bacterial examination of 60 sam- 
ples of milk from both sterilized and unsterilized small-top pails. 
Each number represents two samples taken at the same milking, 
when two cows were milked into a sterilized pail and two into an un- 
sterilized one. All the cows were cleaned and bedded, but the udders 
were not washed. The 60 samples from the sterilized pail showed an 
average bacterial count of 6,306, compared with 73,308 for the un- 
sterilized pail, a difference of 67,002, which represents the average - 
number of bacteria per cubic centimeter introduced through unsteril- 
18989° —18—Bull. 642—4 
