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Transactions of the Canadian Institute. [Vol. \II. 



our results seem to show that these bacteria exist in clumps or masses 

 in such material and the centrifugal process breaks these up and 

 distributes them through the milk. 



These results obtained at Guelph are identical with those obtained 

 by Dunbar and Kister, and go to show that centrifugal purification, as 

 far as bacteria are concerned, is ineffectual. 



Contamination of Milk from the Stable Air. 



Although it is difficult to separate contaminations from animal and 

 milker and that from the air, it is better to consider the latter source of 

 infection separately, as the number of germs floating in the air depends 

 to a great extent upon the amount of dry fodder and straw that may be 

 used in the stable. If manure is not frequently and thoroughly cleaned 

 out, it gets dry and small particles from it help to swell the number of 

 microbes in the air. The greater disturbance of these dusty fodders at 

 any time, the greater will be the germ content of the air at that time. 

 The following data show the number of bacteria per minute deposited 

 in a 1 2-inch pail. In series A. {see Fig. 12), the exposure was made 

 during bedding ; in B. {see Fig. ij), one hour after this operation. 



These results indicate that many bacteria are attached to particles 

 of considerable weight, as they soon settle on the floor. 



Cows are frequently bedded with dusty straw at the very time when 

 milking is going on, a forkful of straw in some instances that have come 

 under my observation, having been thrust under the cow that was being 

 milked. Dusty fodders are often thrown down from the loft when the 

 milking is in progress, filling the stable with dust, every particle of which 

 carries spores of moulds and bacteria. It must be remembered also that 

 very undesirable spores which are very difficult to kill, even by long- 

 continued steam heat, abound in straw and hay. 



