106 PHYSIOLOGY OF THE BACTERIA. 
ment, are drawn into the air by the evaporation of 
the liquid containing them, or, after dessication, by 
the winds. These spores are the point of depart- 
ure of epidemic foci, and their extreme lightness 
explains how readily they are disseminated by the 
winds, 
Water. — Water contains considerable quantities 
of bacteria and especially of germs. Their pres- 
ence in atmospheric water is established by the 
experiments of Lemaire and Gratiolet, — and after 
them by more recent observers, — by means of con- 
densers filled with ice, and placed in the fields and 
for comparison in closed apartments. Rindfleisch 
has since expressed the opinion that the vapor of 
water does not contain spores or bacteria, and that 
telluric waters alone contain them; but Billroth, 
Cohn, and others have proved that Rindfleisch was 
too positive in his statement. 
It is not surprising that telluric waters contain 
such a quantity of bacteria that their existence is 
admitted by all. The dust gathered upon the sur- 
face of stones, of leaves, of fruits, etc., shows upon 
microscopic examination an abundance of germs 
(Marié-Davy, Tissander); the washing of these 
objects and of the soil by the rain transports them 
into the rivers and from the rivers to the sea, 
which contains considerable quantities of them. 
Thus, a drop of water from the Seine, according 
to Pasteur and Joubert, is always fecund, and may 
give birth to several species-of bacteria. The dis- 
tilled water of laboratories also contains germs, and 
