26 Dairy Bacteriology. 



A. INFECTION OF MILK ON THE FARM. 



32. Sources of contamination* The bacterial life 

 that finds its way into the milk while it is yet on the farm 

 may be traced to several sources, which may be grouped 

 under the following heads: Unclean dairy utensils, fore 

 milk, coat of animal, and general atmospheric surround- 

 ings. The relative importance of these various factors 

 fluctuates in each individual instance. 



33. Dairy utensils. Of first importance, are the ves- 

 sels that are used during milking, and also all storage cans 

 and other dairy utensils that come in contact with the 

 milk after it is drawn. By unclean utensils, actually 

 visible dirt need not always be considered, although its 

 presence in cracks and joints of pails and cans is often 

 evident. Unless cleansed with especial care, these places 

 are apt to be filled with foul and decomposing material 

 that suffice to abundantly seed the milk. Soxhlet 1 found 

 that the addition of 0.1 per cent, of sour milk to fresh 

 milk decreased the keeping quality of the latter from 15 

 30 per cent.; the addition of 1.5 per cent, diminished it 

 80 per cent. Where cans are not well cleaned the above 

 amount could easily be added to the milk from the ma- 

 terial that adhered to the walls of the can. 



Through negligence, vessels are often used that are 

 either unfit or are in an improper condition for handling 

 milk. A rusty milk- can often spoils more milk than 

 sufficient to purchase a new vessel. Wooden pails are 

 no longer to be tolerated in a well-regulated dairy. 

 Where possible, vessels should be made of pressed tin. 

 If joints are necessary, they should be well flushed with 

 solder so that they may be easily and thoroughly cleaned. 

 In much of the cheap tinware that is now to be found on 



1 Soxhlet, Ber. d Wanderversammlung bayer. Landwirthe, Oct., 

 1894. 



