426 BACTERIOLOGY. 



prevented subsequent resurrection of the dis- 

 ease germs. 



Works of sanitation have also the effect of 

 interfering with the foo$ requirements of dis- 

 ease germs. In pure soil or in good water the 

 disease germs either cannot multiply on ac- 

 count of the competition of the common germs 

 of putrefaction, or else they adapt themselves 

 to the new and unfavorable conditions of life 

 and suffer loss of their virulence and infective 

 power ; that is, they lose their ability to attach 

 themselves to man, to multiply and to form 

 poisons and they finally become again simple 

 saprophytes. Until recently comma bacilli in 

 water were always sought for in vain, but after 

 the cholera outbreak of 1892 and 1893 the ba- 

 cilli were found in many places and were often 

 present in abundance in the rivers Elbe, Spree, 

 and Seine. These comma bacilli possessed 

 characteristics of such a kind as to cause them 

 to be naturally regarded as cholera bacilli 

 jnodified and rendered more saprophytic by an 

 aquatic existence. It is to be borne in mind 

 in this connection, to be sure, that individual 

 germs may escape this process of adaptation ; 

 but the purer the soil or the water, the less 

 does any such conserving influence come into 

 play and the greater are the chances that the 

 disease germs will succumb in one way or 



