THE STORY OF THE BACTERIA. 67 



commencement of a life-ancl-death struggle be- 

 tween the bacteria and the cells. The cells 

 attempt either to swallow and thus kill and 

 digest the bacteria, or to so closely surround 

 them as to cut off their oxygen and food sup- 

 ply and so destroy them. The bacteria, on 

 the other hand, so long as they can grow and 

 proliferate, produce a poison which may kill 

 the white blood-cells and break up the other 

 tissues round about. 



There is much reason for believing that this 

 is what actually occurs : that the resisting ca- 

 pacity of the body to the incursions of these 

 invisible organisms is largely resident in these 

 lowly organized cells, which in carrying on 

 their simple cellular activities assume the role 

 of defenders of the body against the bacterial 

 invaders. If the conditions are favorable for 

 them the white blood- and other cells may get 

 the upper hand of the bacteria and stop their 

 growth or kill them all off and thus avert the 

 danger. If, on the other hand, the cells are 

 not vigorous enough to resist the poison elimi- 

 nated by the bacteria and themselves succumb 

 to its influence, the way is opened to the spread 

 of the infecting germs. 



