INTROD UCTION xiii 



modation. It holds many things in its hands, but not finally 

 life or death. It has not yet brought to light either *'the 

 philosopher's stone" or '* the vital essence." 



What has already been said affords ample reason for a 

 wider dissemination of the elementary facts of bacteriological 

 science. But there are other reasons of a more practical 

 nature. Municipalities are expending public moneys in 

 water analysis, in the examination of milk, in the inspection 

 of cows and dairies, in the bacterial treatment of sewage, and 

 in disinfection and other branches of public health adminis- 

 tration. Again, the newly formed National Association 

 for the Prevention of Tuberculosis, our increasing colonial 

 possessions with their tropical diseases, even medical science 

 itself, which is year by year becoming more preventive, make 

 an increasing claim upon public opinion. The successful 

 accomplishment and solution of these questions depend in 

 a measure upon an educated public opinion respecting the 

 elements of bacteriology. Recently it was urged that "the 

 first elements of bacteriology should be shadowed forth in 

 theprimary school." ' This course was advised owing to such 

 knowledge being of value to those engaged in dairying. As 

 we shall point out at a later stage, many of the undesirable 

 changes occurring in milk are due to bacteria, even as the 

 success of the butter and cheese industries depends on the 

 use and control of the fermentative processes due to their 

 action. Much of the uncertainty attending the manufacture 

 of dairy products can only be abolished by the careful 

 application of some knowledge of the flora of milk. In 

 Denmark and in Scandinavia the importance of such 

 knowledge is realised and acted upon. America, too, has 

 not been slow to respond to these needs ; but in England 

 comparatively little has been done in this direction.^ 



^ The Contemporary Review, November, 1897, p. 719. 



^•Some notable exceptions are found in the work of the Bath and West of 

 England Society, Lord Vernon's model dairy, and the Essex County Council 

 Bacteriological Teaching Laboratory. 



