182 BACTERIA IN MILK AND MILK PRODUCTS 



disease from some case of infectious disease, such as scarlet fever, 

 in their homes. But under the more efficient registration of such 

 disease, which has recently characterised many dairy companies, 

 the danger of infection from this source has been reduced to a 

 minimum. 



Professor Eussell recounts a simple experiment, which clearly 

 demonstrates these simple but effective sources of pollution: "A 

 cow that had been pastured in a meadow was taken for the 

 experiment, and the milking done out of doors, to eliminate as much 

 as possible the influence of the germs in the barn air. Without 

 any special precaution being taken, the cow was partially milked, 

 and during the operation a covered glass dish, containing a thin 

 layer of sterile gelatine, was exposed for sixty seconds underneath 

 the belly of the cow, in close proximity to the milk-pail. The udder, 

 flank, and legs of the cow were then thoroughly cleaned with water, 

 and all of the precautions referred to before were carried out, and 

 the milking then resumed. A second plate was then exposed in 

 the saine place for an equal length of time, a control also being 

 exposed at the same time at a distance of ten feet from the animal 

 and six feet from the ground to ascertain the germ contents of the 

 surrounding air. From this experiment the following instructive 

 data were gathered. Where the animal was milked without any 

 special precautions being taken, there were 3250 bacterial germs per 

 minute deposited on an area equal to the exposed top of a ten-inch 

 milk-pail. Where the cow received the precautionary treatment as 

 suggested above, there were only 115 germs per minute deposited 

 on the same area. In the plate that was exposed to the surrounding 

 air at some distance from the cow there were 65 bacteria. This 

 indicates that a large number of organisms from the dry coat of 

 the animal can be kept out of milk if such simple precautions as 

 these are carried out." * 



The influence of the byre air, and the cleanliness or otherwise of 

 the byre, is obviously great in this matter. As we have seen, moist 

 surfaces retain any bacteria lodged upon them ; but in a dry barn, 

 where molecular disturbance is the rule .rather than the exception, 

 it is not surprising that the air is heavily laden with microbic life 

 derived from dust, dried manure, hay, straw, fodder, etc. Here again 

 many improvements have been made by sanitary cleanliness in 

 various well-known dairies. Still there is much more to be done in 

 this direction to ensure that the drawn milk is not polluted by a 

 microbe - impregnated atmosphere. Lastly, it should not be 

 forgotten that during the straining and cooling of milk there are 

 many opportunities of contamination. 



The risks in transit differ according to many circumstances. 

 * H. L. Russell, Dairy Bacteriology, p. 46. 



