126 ILLINOIS DAIRYMEN'S ASSOCIATION. 



20 c. c. stripping^, 44. 



In these cases it should be remembered that contamination from all 

 other sources was excluded. The end of the teat was disinfected and a 

 sterile flask placed directly over the same so that no bacteria could gain 

 access from the outside. 



The third factor to which reference will now be made is the influence 

 which the animal herself directly exerts on the germ content of the milk; 

 also the contamination which comes from the dust in the air of the barn. 

 The coat of the cow could be provided in no better way to aid in the 

 distribution of bacteria. Unless kept thoroughly clean, her flanks, under 

 parts and tail become coated with evident filth. Even where this material 

 is not allowed to accumulate there are innumerable dust particles caught 

 in the hair. The majority, of these contain organisms of all sorts 

 bacteria predominating. See what is found on a single hair. By planting 

 in gelatine these hairs taken from the apparently clean coat of a cow, it 

 is possible to study the number and kind of organisms that find their way 



NO. 4. — Showing the bacterial contamination arising from hair. These 

 three hairs were allowed to fall on a sterile gelatine surface. The 

 adherent bacteria developed readily in this medium and the number 

 of bacteria thus introduced into the milk from these hairs can be 

 estimated by the developing colonies that show as irregular protu- 

 berance along the line of the hair. 



