CHAPTER I. 



THE CONTAMINATION OF MILK. 



Uddef. Milk conies 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 Fig- 1 - Section of one quarter of the 



current belief and have udder of a cow at a plane intersectin S 

 Iave the teat and milk cistern. Photograph 



led numerous workers to by the author, from a museum specimen 

 repeat the experiment prepared by Dr. G. S. Hopkins. 



