Household Bacteriology 1389 



contamination amounts to, it has been found that when little care is 

 taken to protect the dishes, the milk will often contain several hundred 

 times as many bacteria as when the utensils were protected from dust. 

 In order to illustrate this point, two pails were carefully washed and 

 sterilized. One of them was covered with sterile cloth to keep dust 

 from falling into it. The other was left exposed to the air of a clean 

 creamery for only a few minutes. A small quantity of sterile milk was 

 then put into each pail, rinsed around, and then examined for numbers 

 of bacteria. It was found that the milk in the pail which was not pro- 

 tected from dust contained 1,600 more bacteria per cubic centimeter 

 than the milk in the protected pail. 



4. " Contamination from the cow's udder and body.— Great numbers of 

 bacteria fall into the milk when it is being drawn from the udder, because 

 the milking pail is directly under the udder which is being shaken more 

 or less by the milker's hands. This kind of contamination may be 

 reduced by cleaning the udder. It was found that sterile milk exposed 

 under the udder as long as it takes to milk a cow, and while the udder 

 was being shaken about the same as when milk is being drawn, con- 

 tained 19,000 bacteria per cubic centimeter. In this case the udder had 

 been wiped off with a dry cloth much in the same way as is done in fairly 

 good dairies. 



" In a similar test, the udder was wiped with a damp cloth and then 

 the number of bacteria was reduced to 4,500 per cubic centimeter. In 

 a third experiment the udder was wiped with a cloth dampened in a 

 4-per-cent carbolic acid solution; then the number of bacteria was 3,200 

 per cubic centimeter. In cases in which no particular care is taken to 

 clean the udder, the bacteria getting into the milk from this source may 

 run up into the hundreds of thousands or millions. 



5. " Importance of small openings in milk pails. — Thus it is seen that 

 it is impracticable to clean the udder or free the air from dust so perfectly 

 that no bacteria will fall into the milk. The next question is, how can 

 we reduce the number of those that will fall in spite of all reasonable 

 precautions? The easiest way known is to use a small-top milking- 

 pail. Reduce the opening through which dirt can fall into the pail. 

 An experiment was conducted to illustrate this point, and it was found 

 that milk drawn in an ordinary milking-pail contained 1,300 bacteria 

 per cubic centimeter, while that drawn in a pail with opening about 

 one half as wide contained only 320 bacteria per cubic centimeter. This 

 is just what we would expect when we compute the number of square 

 inches through which dust can fall into the different kinds of pails. For 

 example, a pail having a top 14 inches in diameter has an opening of 153.86 



