CHAPTER I. 



THE CONTAMINATION OF MILK. 



Udder. Milk comes in contact with bacteria in the lactif- 

 erous ducts of the udder at the moment of secretion. The 

 normal healthy udder of the cow harbors bacteria throughout 



its whole extent. Fig. 1 



shows the extent of the 

 lactiferous ducts of the 

 udder and the direct com- 

 munication with the ori- 

 fice of the teat. 



There was current at 

 one time a belief that the 

 interior of the udder is 

 sterile, except, perhaps, 

 the teats, and that failure 

 to obtain sterile samples 

 of milk was due to con- 

 tamination from bacteria 

 in the teats, or from ex- 

 ternal sources. Moore 

 (41) suggested the 

 method of attacking the 

 problem by the bacterio- 

 logical examination of 

 the normal udders of re- 

 cently slaughtered cows. 

 The results obtained by 

 this method of investi- 

 gation (42, 44, 66, 67) 

 diametrically opposed 

 current belief and have 

 led numerous workers to 

 repeat the experiment 



Fi^. 1. Section of one quarier of the 

 udder of a coi-i< at a plane intersecting 

 the teat and milk cistern. Photograph 

 bv the author, from a museum specimen 

 prepared by Dr. G. S. Hopkins. 



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