SECTION III 



PATHOGENIC MICROORGANISMS 



CHAPTER XX 



AN INTRODUCTION TO THE STUDY OF INFECTIOUS DISEASES 



THE RELATIONSHIP OF BACTERIOLOGY TO THE CLINIC 

 AND TO PUBLIC HEALTH 



THE problem of infectious diseases is peculiar in that, more than 

 any other branch of medicine, it calls for the intimate cooperation 

 of the laboratory worker, the clinician and the sanitarian. It is a 

 subject in many phases of which problems of engineering are im- 

 portant, in which food production plays a part, and to which the 

 educational and sociological agencies of the community as a whole 

 can contribute very materially. The eventual suppression of in- 

 fectious diseases cannot be accomplished by any one of the agencies 

 mentioned, or by all of them together without the cooperation of 

 the public in general. 



In many respects the study of infectious diseases is the most 

 logical branch of medicine at the present time. In many of these 

 conditions we are familiar with the causative agents, we know the 

 manner in which they gain entrance to the body, where they lodge 

 and multiply, where and how they form their secondary foci, what 

 manner of poisons they produce, and what reactions they call forth 

 in the living animal tissues. We can often isolate the bacteria from 

 the bodies of the sick and the dead; we can recognize them when 

 we isolate them in locations outside the body; we can study their 

 biological activities, and their poisons both apart from the animal 

 body and in animal experimentation. Moreover, both in animals 

 and man we can study directly the reactions of the body to invasion, 

 and the agencies by which the invaders are destroyed. 



For these reasons, the first requirement for a thorough clinical 



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