202 BACTERIA IN MILK AND MILK PRODUCTS 



the medium (whether agar or cheese) in which it is growing. What 

 its exact rdle is in milk it would be difficult 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 (DeMpine). 



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 B. coli, and it was declared 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 reserve. The 

 diagnosis of B. coli eight or nine years ago was not such a strict 

 matter as to-day. Still, undoubtedly, this particular organism is not 

 uncommonly found in milk, and its source is uncleanly dairying. In 

 the same investigation, Proteus vulgaris, B. fluorescens, and many 

 liquefying bacteria were frequently found. Their presence in milk 

 means contamination with putrefying matter, surface water, or a 

 foul atmosphere. 



A number of water bacteria find their way into milk in the 

 practice of adulteration, and foul byres, and dirty dairies and milk 

 shops, afford ample opportunity for aerial pollution. 



Another unclassified group occasionally present in milk is repre- 

 sented by moulds, particularly Oidium lactis, the mould which causes 

 a white fur, possessing a sour odour. It is allied to the Mycoderma 

 albicans (0. albicans), which also occurs in milk, and causes the 

 whitish-grey patches on the mucous membrane of the mouths of 

 infants (thrush). These and many more are occasionally present in 

 milk. 



2. The Disease-peoducing Power of Milk 



The general use of milk as an article of diet, especially by the 

 younger and least resistant portion of mankind, very much increases 

 the importance of the question as to how far it acts as a vehicle of 

 disease. Recently, considerable attention has been drawn to the 

 matter, though it is now a number of years since milk was proved to be 

 a channel for the conveyance of infectious diseases. During the last 

 twenty years, particular and conclusive evidence has been deduced 

 to show that milch cows may themselves afford some measure of 

 infection. The extensive work on tuberculosis by three Eoyal Com- 

 missions has done much to obtain new light on the conveyance of 

 that disease by milk and meat. The enormous strides in the know- 

 ledge of the bacteriology of diphtheria and other germ diseases have 

 also placed us in a better position respecting the conveyance of such 

 diseases by milk. Generally speaking, for reasons already given, 

 * Brit. Med. Jour., 1895, vol. ii., p. 322. 



