INFECTION 3 



possibly the death of the individual. The invading microor'- 

 ganisnis may belong to any one of the three great groups of 

 microscopic life, namely, bacteria, higher fungi, and protozoa. 

 It is customary and convenient, if not altogether logical, to 

 limit the term microorganisms to these forms, excluding alto- 

 gether the entozoa and other animal parasites, most of which 

 are not microscopic in size. 



A diseased condition produced by substances not capable 

 of reproducing themselves, as, for example, organic or inor- 

 ganic chemical compounds, is an inioxicative process. In an 

 infection, the immediate cause of the symptoms and morbid 

 changes in the tissues is an intoxication due to the action of 

 the metabolic products (toxins) of the invading microorgan- 

 isms. The theories of their mechanical interference with 

 the normal functions of the body or that they absorb the 

 nutriment, thus depriving the tissues of necessary food, wait 

 for demonstration. The results of infection vary in their 

 manifestations. 



If the invading organisms remain at the point of entrance 

 and produce local tissue changes, the condition is spoken of as 

 a wound infection. 



If the invading bacteria become widely distributed in the 

 circulation and tissues, the condition is known as ^pticemia or 

 bacteremia. 



If the infecting bacteria remain at the point of entrance 

 and multiply there, elaborating a toxin which is absorbed and 

 which causes symptoms and possibly death, the condition is a 

 toxemia. 



If there is a febrile condition, resulting from the absorp- 

 tion of the products of putrefaction caused by saprophytic 

 bacteria, the condition is called sapremia. 



If the invading organism is one possessed of definite 

 pathogenic properties, such as the bacterium of anthrax, giv- 

 ing rise to a definite series of symptoms and lesions, the affec- 

 tion is designated a specific, infectious disease. 



Through the agency of metastasis, invading microorgan- 

 isms may be carried from the point of introduction to other 



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