Invasion of the Udder by Bacteria. 299 



cistern and its larger ramifications, in order to show the lining 

 mucous membrane of those cavities. Since the udder was not 

 secreting milk when the cow was killed, the glandular tissue occu- 

 pied the minimum amount of space. This resulted in a general 

 darkening of the udder by the lampblack without the contrast which 

 would have shown more clearly the individual lactiferous ducts. 



The free communication of the milk cistern with the more minute 

 lactiferous ducts is at times interrupted by the sphincter muscles 

 described by anatomists as present in those ducts. There is little 

 ground, however, for considering them as serious barriers to the 

 progress of micro- organisms one twenty-five thousandth (^-g-tinr) ^^ 

 an inch in diameter. 



That the milk ducts of the teat normally harbor bacteria is 

 admitted by all. Some few, with whom the writer agrees, assert 

 that the milk cistern normally harbors bacteria. Such being true, 

 there is little reason to doubt that bacteria may find their way through 

 the fine ramifications of the milk cistern (lactiferous ducts) to regions 

 remote from the teat. Pathogenic organisms certainly do so when 

 the udder is diseased and to conceive that harmless ones do so in 

 health is not difiicult. 



The Importance of the Problem. 



It will be noted that none of the species of micrococci isolated 

 from the udders are capable of rapidly souring milk. They are, on 

 the contrary, inert as regards their immediate visible effect. A 

 similar fact has been noted by Dinwiddie* in regard to the bacterial 

 fiora of the fore milk of two cows studied by him. 



Bolley t likewise has expressed his belief " that comparatively few 

 forms may multiply within the normal udder, and that these are 

 perhaps scarce to be considered as detrimental forms." 



The writer has repeatedly isolated micrococci from the fore milk 

 of the University herd, apparently identical with some of those 

 found in the udders of the freshly slaughtered milch cows from the 

 herds mentioned elsewhere in this bulletin. 



*K. R. Dinwiddle, Arkansas Agricultural Experiment Station, Bulletin No 

 45, p. 56. 



fH. L. Bolley, North Dakota Experiment Station, Bulletin No. 21. 



