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 

 (Marie"-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 



