MICRO-ORGANISMS IN MILK 335 



countries, chiefly in Denmark, for the removal of insoluble dirt. 

 Dirt particles are, of course, removed by filtration, but the bac- 

 terial content is not decreased, if the colony count is taken as 

 index. A filter which is capable of retaining bacteria would 

 also retain fat globules, as these on the average are larger than 

 bacteria. 



Aeration has been resorted to in order to ehminate disagreeable 

 odors. The milk is brought in contact with the air by pouring it 

 in thin layers from one can to another, or by using open coolers. 

 Odors are largely removed by this process, but there is danger of 

 additional contamination from the air, and clean milk does not 

 need aeration. 



In some dairies the milk is strained several times before it is 

 ready for shipment. It may be strained into the milking pail, 

 then into a large can, and finally again before it passes to the 

 cooler. This frequent straining tends to increase the colony 

 count because the dirt that is retained on the strainer is broken 

 up by succeeding amounts of milk poured on it, and finally in 

 part passes through the strainer. The strained milk, therefore, 

 contains more single bacteria than the unstrained milk. In a 

 series of experiments carried out by the writer with Luckhardt 

 and Hicks it was found that the average of 80 samples contained 

 2060 bacteria per cubic centimeter before straining and 2790 after 

 straining. Milk squeezed from the cotton strainer contained 

 3912 bacteria per cubic centimeter. These figures show that 

 although an appreciable number of bacteria were retained in the 

 cotton, the colony count of the strained milk was higher than that 

 of the unstrained milk. These tests were carried on in a high- 

 class dairy and the conclusion is obvious that in an ordinary dairy 

 the difference would be greater. It follows that frequent strain- 

 ing is not conducive to reduction of the germ content. 



These methods of making milk attractive have some advan- 

 tages. The consumer does not see the dirt collect at the bottom 

 of the bottle and the milk has a sweet taste and odor unless the 

 pollution has been so heavy that soluble substances are present 

 in excessively large quantity. 



The modern milk bottle is designed more with convenience in 

 view than sanitation. The wide mouth of the bottle facilitates 

 washing, but the shoulder on which the pulp cap rests may retain 

 dirt that falls on the bottles during transportation. Bottles with 

 small necks can be thoroughly cleaned with appropriate machines 

 and would do away with some of the disadvantages of the wide 

 mouth bottle now generally in use. It is true that a change from 

 the present style of bottle to a narrow neck bottle would meet 

 with some practical difficulties which, however, time will have to 



