THE MICROBES OF HUMAN DISEASES. 165 



and Belleville, crowded and populous quarters, in which 

 are also cemeteries and slaughter-houses. 



It has long been established that the air is much 

 purer on high mountains or on the sea, than in plains 

 and in the vicinity of inhabited places. If glass flasks 

 which have been previously sterilized and deprived 

 of air are taken to a great height on the Alps or 

 Pyrenees, and. then filled with air, it will be difficult 

 to detect any microbes, and the few which may be 

 found are possibly brought by the observer. So 

 again, on the top of the Pantheon, a cubic metre of 

 air only contains 28 microbes, while 45 are found in 

 the park of Montsouris, and 462 in the centre of 

 Paris. 



The Microbes of Running and Drinking Water. 

 Water, whatever be its source, contains many more 

 microbes than air. They are even found in spring- 

 water taken from its source, which shows that they 

 exist in the interior of the earth. The following is 

 Miquel's estimate, which will give an idea of the 

 quantity of microbes found in Paris water, taken from 

 different places : 



Source of water. No. of microbes 



to the litre. 



Condensed aqueous vapour ... . . . ... 900 



Water from drain, Asnieres 48,000 



Rain-water 64,000 



Vanne water (Montrouge basin) 248,000 



Seine water (from Bercy, above Paris) 4,800,000 



Seine water (from Asnieres, below Pari-,) ... 12,800,000 



Sewer-water (from Clichy) ... 80,000,000 



