44 THE STORY OF THE BACTERIA. 



into his beer some chemical substance which 

 is innocuous to them but deadly to the intrud- 

 ing bacteria. Or he may raise his wine at a 

 certain period to such a temperature as will 

 suffice to kill the bacteria but not injure the 

 flavor of the already fermented juice. Here 

 for the first time we see the bacteria coming 

 in conflict with the purposes of their earth- 

 neighbor man. 



Some of the bacteria are great lovers of 

 oxygen, and if they are shut up in a little cell 

 containing a few drops of water in which a bub- 

 ble of air has been enclosed, after a while it will 

 be found that those forms which are caoable 

 of locomotion have made their way from 

 all parts of the fluid, which is a veritable ocean 

 to them, and are closely clustered around the 

 air bubble, jostling and bumping against one 

 another in the most reckless way. It seems 

 almost as if this rush towards the oxygen were 

 an evidence of volition in its simplest form 

 way down on the lowest border-line of life. 



Some forms of bacteria are exceedingly in- 

 vulnerable to the action of cold, and can not 

 only move actively about in very cold water, 



