HEALTH AND THE LAWS OF MECHANICS 139 



mouth. This chemical disturbance of the medium 

 in which the microbes of pneumonia and diphtheria 

 and others live carries with it a modification of 

 these kinds of microbes in order to adapt them- 

 selves to their new conditions of life, and in them 

 resides the acquisition of properties which give 

 them virulence, and which may produce pneumonia, 

 for instance. In a sound individual, in the fullest 

 acceptance of the term, such things do not happen ; 

 but there are many who, though apparently robust, 

 are not healthy, as they have an organic disorder, 

 as happens with all arthritic subjects. If, among 

 these, causes supervene which increase the arthritic 

 tendency, as excessive fatigue, moral depravity, or 

 some other depressing cause, it may happen that 

 the liquids of the mouth undergo the changes 

 necessary for the microbe of pneumonia, which 

 till then lived harmless, to acquire the virulence 

 which converts it into the terrible agent of pneu- 

 monia. Take also into account that, when these 

 circumstances occur in the case of an arthritic 

 subject, not only are the juices of the mouth 

 changed, but also all those of his organism, which 

 increases predisposition to it, and aggravates the 

 consequences. 



What happens with the microbe of pneumonia, 

 diphtheria, suppuration, etc., may be applicable to 

 all infectious agents that are normal organisms 



