Bacteria as Man's Invisible Foes 63 



in another, sometimes everywhere, and grad- 

 ually or suddenly that combination of activ- 

 ities 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 ex- 

 haustion 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 

 communities which we call liver, brain, kid- 

 neys, lungs, integument, and so forth, pro- 

 vided^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 overcoming and resisting dele- 

 terious 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 



