RELATION OF BACTERIA TO DAIRY INDUSTRY. 69 



for the farmer rarely grooms his cow, and during 

 the milking, by her movements, by the switching 

 of her tail, and by the rubbing she gets from the 

 milker, no inconsiderable amount of this dirt and 

 filth is brushed off and falls into the milk pail. 

 The farmer understands this source of dirt and 

 usually feels it necessary to strain the milk after 

 the milking. But the straining it receives through 

 a coarse cloth, while it will remove the coarser 

 particles of dirt, has no effect upon the bacteria, 

 for these pass through any strainer unimpeded. 

 Again, the milk vessels themselves contain bac- 

 teria, foi they are never washed absolutely clean. 

 After the most thorough washing which the milk 

 pail receives from the kitchen, there will always 

 be left many bacteria clinging in the cracks of the 

 tin or in the wood, ready to begin to grow as 

 soon as the milk once more fills the pail. The 

 milker himself contributes to the supply, for he 

 goes to the milking with unclean hands, unclean 

 clothes, and not a few bacteria get from him to 

 his milk pail. Lastly, we find the air of the milk- 

 ing stall furnishing its quota of milk bacteria. 

 This source of bacteria is, however, not so great 

 as was formerly believed. That the air may con- 

 tain many bacteria in its dust is certain, and 

 doubtless these fall in some quantity into the 

 milk, especially if the cattle are allowed to feed 

 upon dusty hay before and during the milking. 

 But unless the air is thus full of dust this source 

 of bacteria is not very great, and compared with 

 the bacteria from the other sources the air bac- 

 teria are unimportant. 



The milk thus gets filled with bacteria, and 

 since it furnishes an excellent food these bacteria 

 begin at once to grow. The milk when drawn is 



