424 N'ovman MacDonald : 



bacteria through the orifice of the teat duct between 

 milkings. 

 In regard to the machine the chief sources of contamination 

 are likely to be : — 



1. The surface of the teat, which is being intermittently 



washed by the milk as withdrawn. 



2. Air drawn into the cup at each pulsation through the 



small '' air admission " aperture. 



3. Bacteria within the teat duct. 



4. Dirt within the apparatus itself. 



It would seem therefore that the possible sources of infection 

 are greater for the hand-drawn than for the machine-drawn 

 milk, for the latter is but little exposed to contamination by the 

 milker's hands, by the skin of the cow, or by dust and manure 

 particles, as the receptacle is covered during the whole process 

 of milking. 



On the other hand if the mechanical apparatus be not 

 thoroughly cleansed after use and small quantities of milk be 

 allowed to remain in different parts between the times of milk- 

 ing, a suitable medium for the rapid multiplication of bacteria 

 is provided, and a fertile source of danger is bound to be 

 established. 



In the investigation under review an endeavour was made to 

 eliminate as far as practicable each and all of these sources 

 of contamination in both the hand and the machine milking. 

 For example, cleanliness in regard to the milker's hands and 

 garments was insisted upon ; washing the cow's udder and teats, 

 and grooming the flanks with a damp brush was practised. The 

 first ounce or two of the fore milk was withdrawn by hand 

 and discarded, and in the case of the machine the apparatus was 

 thoroughly sterilised, as can be seen by the supervisor's report 

 already quoted ; while the premises were kept in a thorough 

 slate of cleanliness. 



For the purpose of the comparative test, four cows were 

 selected, all being approximately of the same age, breed and 

 condition, and each giving about the same quantity of milk. 

 TSvo were carefully milked by hand and two by machine. 

 Fair samples from the total supply of each pair were placed 

 by Mr. McAdam, the supervisor, in sterile bottles, securely 



