NORMAL AND ABNORMAL MICROFLORA OF MILK 69 



milk may be poisonous on account of toxins which have passed 

 into it as the result of fevers or serious digestive troubles. 



An indirect influence may of course be exercised by diseases of 

 the udder, among which inflammation of the udder or mastitis and 

 tuberculous udder are the most important. The alterations in the 

 composition of the milk are bacteriological as well as chemical. 

 In the first place the reaction of the milk- is altered ; frequently it 

 becomes alkaline rather than neutral, due to the inflammation 

 produced by Streptococcus mastitidis, though as a rule it eventually 

 becomes acid as this organism produces appreciable amounts of 

 lactic acid. The milk acquires a bitter, salt or other unpleasant 

 taste, and the percentage of lactose, the most constant factor in 

 the milk as long as the udder remains healthy, falls off appreciably. 

 Flakes and lumps of pus and casein will be seen in the milk, and 

 the colour changes. With streptococcic mastitis the milk becomes 

 yellow, and with tuberculous udder bluish. Occasionally the 

 milk may be coloured red by blood, and generally speaking, 

 increasing quantities of the constituents of the blood pass into the 

 milk while the normal constituents of the milk fall off. At last a 

 watery secretion containing pus is obtained which can no longer 

 be described as milk. 



Inflammation of the Udder. The most dangerous form of this 

 disease is that caused by Streptococcus mastitidis. It is very 

 infectious, being easily transmitted from one cow to another, so 

 that for this reason alone it is desirable that the milker's hands 

 should be washed after milking each cow. Inflammation of the 

 udder is also occasioned by Bacterium pyogenes and certain coli 

 and aerogenes bacteria and micrococci. B. pyogenes is a very 

 small rod form which may produce a very unpleasant smell in 

 the milk. A similar form, Bacterium minimum mammae, which 

 decomposes casein, but does not liquefy gelatine, and which 

 produces small amounts of lactic acid, has been found repeatedly 

 by Gorini x in the udders of cows which have not been milked 

 properly. Under these conditions, micrococci, possibly the same 

 as those which are normally found in and on the udder, may gain 

 predominance. This may also happen if the udder is in an 

 unhealthy state owing to chills. The micrococci generally only 

 produce light catarrhs. Bacterium pyocyaneum may also be 

 found in inflamed udders. 



As most of the bacteria mentioned here may give rise to stomach 

 and intestinal diseases, milk from inflamed udders must be 

 regarded as dangerous. 



Udder and other Tuberculosis. Owing to the prevalence of 



1 " Revue generate du Lait," 1907, Vol. VI., No. 24. 



