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 Kucalyptus 
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. Hyqrent 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 
