CHANGES JX MILK 51 



VII. CHANGES IN MILK CAUSED BY 

 MICRO-ORGANISMS 



Milk found in the glandular passages and cisterns of 

 tlie healthy udder is usually sterile. On the other hand, 

 the duets of the teats and, still more, the ends of the 

 teats usually contain hacteria and, therefore, the milk 

 when drawn is infected with them. This is more apt to 

 he the case when the milk comes in contact with the 

 liands of the milkers, oi- when it is poured into the not 

 always sterik' bucket, or when particles of dirt and dust 

 from the udder or the skin of the cow, from the clothing 

 of the milkers oi- from the air, dro^) into the milk. 

 IV'forc the milking is finished, a considerable number of 

 tlifferent bacteria have been added to the milk and 

 though, for a time, it has bactericidal iin)i)crtics, that 

 is, it is able to kill bacteria or, at least, to pi'evcut their 

 .growth, yet the number of bacteria docs not diminish 

 noticeabi}- but, in the course of time, increases enor- 

 mously. Shortly after milking, thousands, even hun- 

 dreds of thousands, of bacteria may be found in encli 

 cul)ic centimetre. 



In inflammatory processes, catarrh, ttiberculosis and 

 ;!ctinomycosis of the udder, infected wounds at the open- 

 ing of the teat, etc., bat-teria are more or less numerous 

 in tlic milk before it is drawn. In benign udder inflam- 

 mations liacteria disappear almost entirely with the 

 cessation of the disease, but occasionally it happens that 

 the bacterial growth continues for a time in the milk 

 contained in tlu' glandular passages, after the secretion 

 has liecome api)arently (juite normal and after all signs 

 of inflammation have disajjpeared 



In general infections, not locaUzed in the udder, as 

 a rule no microbes are excreted with the milk. An excep- 

 tion to this is foot-and-mouth disease (aphthous fever), 

 in which the milk of the affected cows often contains vir- 



