vi PEEFACB. 



of the beings in question, or could give an exact 

 account of the function which microbes fulfil in 

 nature. And yet this function concerns us all. 



The man of the world who desires to take part in 

 a scientific discussion ; the lawyer who has to treat of 

 a question of hygiene in the presence of experts ; the 

 engineer, the architect, the manufacturer, the agricul- 

 turist, the administrator — all have to consider such 

 questions, and they will find in this work clear and 

 precise notions on microbes, notions which they wo]|id-^' 

 find it difficult to glean from books designed for 

 physicians and professional botanists. 



The questions of practical hygiene, those which 

 concern domestic economy, agriculture, and manufac- 

 tures, and which are connected with the study of 

 microbes, must especially demand attention. These 

 are pertinent questions in such a book as this. There 

 is a certain danger in vulgarizing notions of medicine, 

 strictly so called; but it can only be beneficial to 

 iriake every one acquainted with the precepts of hy- 

 giene, which cannot become popular untU they have 

 penetrated into the habits and routine of national 

 life. 



There is much to be done before modem society 

 is practically on a level with the achievements of 

 science ; many prejudices must be uprooted, and many 



