194 BACTERIA 



This is an actively motile rod, the presence of which does 

 not materially affect the milk, but causes the milk products 

 to be of poor quality. 



Yellow Milk. Bacillus synxanthus is held responsible for 

 curdling the milk, and then at a later stage, in redissolving 

 the curd, produces a yellow pigment. 



Violet and Green Pigments in milk are also the work of 

 various bacteria. 



2. Various Unclassified Bacteria 



In milk this is a comparatively small group, for it happens 

 that those bacteria in milk which cannot be classified as 

 fermentative or pathogenic are few. The almost ubiquitous 

 Bacillus coli communis occurs here as elsewhere, and might 

 be grouped with the gaseous fermentative organisms on ac- 

 count of its extraordinary power of producing gas and break- 

 ing up the medium (whether agar or cheese) in which it is 

 growing. What its exact role is in milk it would be diffi- 

 cult to say. It may act, as it frequently does elsewhere, by 

 association in various fermentations. Some authorities hold 

 that its presence in excessive numbers may cause epidemic 

 diarrhoea in infants. 



Several years ago a commission was appointed by the 

 British Medical Journal to inquire into the quality of the 

 milk sold in some of the poorer districts of London. Every 

 sample was found to contain Bacillus coli, and it was de- 

 clared that this particular microbe constituted 90 per cent, 

 of all the organisms found in the milk.' We record this 

 statement, but accept it with some misgiving. The diag- 

 nosis of B, coli four or five years ago was not such a strict 

 matter as to-day. Still, undoubtedly, this particular or- 

 ganism is not uncommonly found in milk, and its source 

 is unclean dairying. In the same investigation Proteus 



* British Medical yournal, 1895, vol. ii., p. 322, 



