80 BRITISH DAIRYING. 



odours of the cowshed are often traceable in milk, but this is 

 chiefly owing to the cow herself; she breathes them into her 

 lungs, where they come in contact with her blood, and so they 

 are communicated to the milk. This, in fact, is the " cowey " 

 smell, which is only effectually got rid of by passing the milk 

 over a refrigerator. 



But it is not by odours only that milk becomes contaminated, 

 and the odours are comparatively easy to deal with. In addi- 

 tion to them there are various kinds of bacteria or micro- 

 organisms in the air, and these are apt to work out their destiny 

 in so congenial a fluid as milk. They exist too in vessels 

 which, having contained milk before, have not been thoroughly 

 scalded and cleaned. The term " fermentative," as employed 

 in the following quotation, covers not only the souring, but 

 also the curdling and putrefaction of milk. 



It has been ascertained that there are various forms of degra- 

 dation through which milk may pass, the results arising from 

 the action of microbes, bacteria, or fungi. As one writer 

 expresses it : "There is the premature souring of milk with- 

 out any curdling, the thickening of it without souring, the 

 appearance of green and blue mould and the red fungus, the 

 swelling or foaming of the cream in the churn, or the change of 

 it to a thin watery liquid having a bitter taste. Briefly, then, 

 the normal souring of milk is a fermentative process produced 

 by organisms that get into the milk after the milking is done. 

 These organisms all get into the milk from external sources, 

 such as air, the hands of the milker, the hair or udder of the 

 cow, and especially from the vessels into which the milk is 

 drawn. It follows that the number present in the milk will 

 vary with the amount of cleanliness used in the dairy and barn. 

 If the udder of the cow be carefully cleaned and the milk be 

 drawn into a glass tube which by heating has been made free 

 from all living germs, and which can be closed so as to keep 

 from the milk all air, milk will be got so free from bacteria that 

 it will remain unaffected for two weeks, even though kept ali 

 the time in a warm temperature." 



In practical dairying it is next to impossible to keep all these 



