Invasion of the Udder by Bacteria. 283 



The writer"^ has conchicled, chiefly from a study of the bacterial 

 flora of fore milk that (1) certain species of bacteria normally persist 

 in particular quarters of the udder for considerable periods of time. 

 (2) It is possible for bacteria to remain in the normal udder and not 

 be ejected along with the milk. Tliese conclusions controvert the 

 statement that the milk ducts are always sterile at the close of the 

 milking, becoming tenanted from the outside alone by organisms 

 which chance to come in contact with the end of the duct. 



Moore pointed out the importance of a study of the bacterial 

 flora of the normal udder, and to that end suggested that bacterio- 

 logic examinations should be made of the udders of freshly -killed 

 milch cows. After making a fruitless eifort to obtain udders for 

 the purpose from sound cows, he deemed it expedient to avail him- 

 self of opportunities offered by the slaughter of tuberculous milch 

 cows. In January, 1898, Dr. Moore and the writer, who was priv- 

 ileged to associate with him, were given opportunity to examine the 

 udders of six cows, slaughtered after reacting to the tuberculin 

 test. The animals were apparently in good condition and the udders 

 normal in appearance. The port mortem examinations showed the 

 tubercular lesions to be restricted to a few small nodules in the 

 branchial and pharyngeal glands.f After the bacteriologic examina- 

 tion tlie udders were carefully scrutinized for tubercular or other 

 lesions without finding them. The results of those examinations, 

 briefly given in a former publication, :j: opened up a broad and 

 almost totally unexplored field of research for dairy bacteriologists. 



The present publication contains a more extended account of the 

 methods employed and the results obtained from examinations 

 made in co-operation with Dr. Moore and of subsequent ones con- 

 ducted by the writer independently. The udders of nineteen milch 

 cows from five different dairies have been examined. Six of these, 

 Group I, were made at Elmira, as already noted ; two, Group II, at 



* A. R, Ward, The Persistence of Bacteria in the Milk Ducts of the Cow's 

 Udder. Journal of Applied Microscopy, Vol. I, No. 12, p. 205. 



f The fact that the six animals were selected as the least diseased out of a herd 

 of seventy-five condemned animals explains the apparently remarkable restric- 

 tion of the tubercular lesions. 



t V. A. Moore and A. R. Ward, Bulletin No, 158, Cornell University Agricul- 

 tural Experiment Station. 



