SOURCES OF COMMON MILK BACTERIA 73 



have been devised by which the amount of dirt can be quickly 

 determined. These are intended to be used by milk inspectors 

 in their ordinary routine examination of market milk. They 

 have not as yet come into common use. 



A brief summary of the facts of this chapter may be useful. 

 The bacteria that get into the milk from the udder are mostly 

 cocci. Most of these are harmless, and they will always be 

 found. Some appear to be identical with forms that are asso- 

 ciated with various forms of inflammation, and if these be 

 abundant they may make the milk unwholesome. None of them 

 have any noticeable effect on the milk. An unusual number of 

 Streptococci is usually accompanied with pus cells, and injures 

 the milk. The bacteria that get into the milk from other sources 

 are those common in air, soil and water, most of which are 

 harmless. Among these are two types of lactic acid bacteria, 

 various forms of putrefactive organisms and large numbers of 

 miscellaneous species. From these sources, too, come the 

 bacteria that occasionally produce trouble, such as those causing 

 slimy milk, blue milk, tainted milk, sweet curdling, etc. Some 

 of these produce great losses in cheese-making by causing un- 

 desirable flavors. The putrefactive bacteria are always unde- 

 sirable but fairly common. From the milker or dairyman may 

 come certain dangerous disease germs. 



Nearly all dairymen, to-day, have come to recognize the de- 

 sirability of keeping the number of bacteria as small as possible 

 in milk, and are looking for methods by which this can be done. 

 In order to consider intelligently methods by which a dairy can 

 accomplish this it will be necessary to learn certain important 

 facts concerning bacteria growth. The practical application of 

 the facts just given will therefore be reserved for a later 

 chapter. 



