RELATION OF UACTKKIA To THE DAIRY. 1/9 



milking, every motion of her legs, and every rubbing or brush- 

 ing of her body by the milker, dislodges particles of this 

 material which are sure to fall into the milk pail. All of this 

 filth is crowded with bacteria in excessive numbers, and these 

 find their way into the milk during the whole of the milking. 

 Here again actual tests have shown the extent of this source 

 of contamination, and have demonstrated that during the milk- 

 ing a perfect shower of dirt particles laden with bacteria are 

 falling into the milk. Hundreds of bacteria have been counted 

 on a single short hair. The amount of dirt can even be ap- 

 proximately calculated and has in some cases been found to be 

 as much as 25 mg. per quart, equivalent to 300 to 500 Ibs. 

 per day for the supply of a city like New York. The dirt 

 thus found includes excrement, hay, hair, skin, earth, etc., etc., 

 and nearly every particle will be covered with bacteria. Here 

 is evidently one of the prolific sources of milk bacteria. Any- 

 thing which will improve the cleanliness of the cow will im- 

 prove the milk. Even the custom of moistening the under 

 surfaces of the cow with a moist sponge immediately before 

 milking will be of advantage by checking this constant shower 

 of dried particles which fall from the body. 



Devices for removing the larger part of this filth from the 

 milk have been invented and are coming more and more into 

 use. The most common method consists in filtering the milk 

 through deep layers of sand. Quite a number of such filters 

 have been patented and new ones are constantly appearing. A 

 different, and in some respects, a better method, uses centrifugal 

 force for the purpose. By passing the milk through a centri- 

 fugal machine which does not rotate fast enough to separate 

 the cream, a large part of the dirt may be thrown out and 

 easily removed. The milk is thus much improved so far as 

 concerns wholesomeness. This centrifugal purification does 

 not materially affect the bacteria, for there seem to be about as 

 many after treatment as before. 



