MEANS OF DEFENCE AGAINST MICROBES. 245 



germs. Alcohol, which has been long in use, boracic 

 acid, salicylic acid, thymol (essence of thyme), and 

 eucalyptol (the essence extracted from Eucalyptus 

 globulus), and many other substances, have been 

 employed both internally and externally with this 

 object, and most of them take a more or less impor- 

 tant place in the therapeutics of those diseases caused 

 by microbes. 



II. HYGIENE OF DRINKING-WATER: WATER FREE 

 FROM MICROBES ; CHAMBERLAND FILTER. 



The researches carried on by Miquel for some years 

 at the Observatory of Montsouris, at the Pantheon, 

 and in other parts of Paris, teach us that living 

 bacteria are more rare in the atmosphere than had 

 been generally supposed. We have already said that 

 air is the great purifier of microbes, which it destroys 

 by desiccation. Even in the infection of wounds, it 

 is probable that the liquids and linen formerly 

 employed for dressings transported the microbes in 

 greater number than the air, however charged it 

 might be with these organisms in the neighbourhood 

 of a hospital. 



In the water which supplies large towns, whether 

 furnished from wells or streams, a large number of 

 microbes are, however, found in a state of perfect vitality. 

 This is quite natural, since we know that these plants 



