PHENOMENA OF INFECTION. 8i 



is also recognized. This relates to a susceptibility of 

 certain organs or tissues as a result of other concurrent 

 infections. Thus, rheumatism predisposes to infections 

 of the heart; diabetes, to suppurative inflammations 

 (carbuncles) and gangrene of the skin and subcutaneous 

 tissues; enlarged tonsils and adenoids to colds, tonsil- 

 litis, and probably diphtheria. 



Under environment is included all those 

 external influences by which man is sur- 



MENT. . ^ 



rounded which, by exercising a deleterious 

 influence upon health, predispose him to disease. 

 Among such influences are region, season, occupation, 

 food, unhygienic surroundings, previous disease, poisons, 

 injuries, etc. 



Locality may act as a predisposing cause 

 Region, in many ways, all of which may be grouped 



under two heads, viz., (i) climate, and (2) 

 physical conditions. 



Climatic conditions, as is well known, 

 Climate, differ widely in various parts of the world, 



from which arise for the most part great 

 differences in plant and animal life. Moreover, practi- 

 cally everywhere, there are seasonal variations more or 

 less pronounced, which have their corresponding in- 

 fluence upon all living things. In tropical and sub- 

 tropical countries where a high mean temperature and 

 a maximum amount of moisture predominate, the 

 luxuriance of the foliage and the multiformity of animal 



