CAUSES OF DISEASE. 9 



of finding lodgment in an appropriate situation within 

 the body.* 



Infectious agents are divided into those 

 Specific and that are specijic, and those that are non- 

 NoN-sPECiFic specific. By specific is understood an 

 Infectious organism that ahvays provokes the same 

 Agents. disease; at the same time it impHes that 



it is the only exciting cause of that disease. 

 The microbes which cause typhoid fever, diphtheria, 

 plague, etc., are specific agents, because they are the 

 only germs, respectively, that can give rise to these 

 diseases. 



A non-specific agent is an organism whose entrance 

 into the body is not necessarily followed by the same 

 disease, in fact, its effects are particularly characterized 

 by their dissimilarity; besides, its action is duplicated 

 by other non-specific agents. The streptococcus 

 pyogenes is a most excellent example of a non-specific 

 agent. The following are some of the diseases it 

 provokes: Erysipelas, puerperal fever (child-bed fever), 

 tonsillitis, peritonitis, abscess, etc., all affections that 

 exhibit a widely divergent symptomatology, and each one 

 of which may result from entrance into the body of 

 an entirely different species of bacterium. 



*From one view-point, all infectious agents are parasites, just as we 

 will see later they may also be saprophytes. But the true parasite is 

 never an infectious agent. 



