THE STORY OF THE BACTERIA. 55 



which we call life disappears, and the worn-out 

 mechanism for the first time since it came into 

 being is still. This is death. There is no 

 disease, but, as we are apt to say not because 

 it means much, but because we think we must 

 say something, an exhaustion of the vital 

 forces. The mechanism is worn out, and so 

 can no longer develop out of food and air the 

 self-renewed impelling force. It is death from 

 old age. But this is comparatively infrequent. 

 If the proper food, air, and surroundings are 

 maintained, the various co-ordinated cell com- 

 munities which we call liver, brain, kidneys, 

 lungs, integument, and so forth, provided they 

 are properly set going in the first place, have 

 not only the power to go on doing their work, 

 but they have a well marked capacity for over- 

 coming and resisting deleterious agencies of 

 one kind and another, a sort of health inertia. 

 The muscle cells do make shift to contract 

 even though their food supply be temporarily 

 scanty ; the blood cells will carry a certain 

 amount of oxygen in their ceaseless rounds of 

 visits to the tissues, though the air from which 

 they get it through the lungs be as foul and 



