BACTERIA IN FOODS 1 83 



oughly 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 same place for an equal 

 length of time, a control also being exposed at the same time at 

 a jiistance 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 gath- 

 ered. Where the animal was milked without any special precau- 

 tions 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 surround- 

 ing 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 pre- 

 cautions as these are carried out." ^ 



The influence of the barn air, and the cleanliness or other- 

 wise of the barn, 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. 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. 



The risks in transit differ according to many circumstances. 

 Probably the commonest source of contamination is in the 

 use of unclean utensils and milk-cans. Any unnecessary 

 delay in transit affords increased opportunity for multipli- 

 cation ; particularly is this the case in the summer months, 

 for at such times all the conditions are favourable to an 

 enormous increase of any extraneous germs which may have 



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



