CHAPTER VIII. 



PRINCIPLES OF THE CLASSIFICATION OF 

 INFECTIOUS DISEASES. 



IN every infectious disease, the pathologic manifestations 

 are produced by the action of antigens on tissues and organs 

 and the differences in the evolution of symptoms of these 

 different diseases are determined by: 



1 . The physicochemical composition and the physiological 

 properties of antigens and antibodies. 



2. The nature of the compounds formed by antigens with 

 their normal antibodies, whether soluble or insoluble, neutral 

 or active. 



3. The elective affinities of antigens for certain tissues. 



4. The physiological role of the antibodies in the life of 

 those cells which fix the antigen. 



5. The role of the fixing cells in the life of the organism. 



6. The adaptation of the infecting bacteria to life in the 

 infected organism. 



7. The nature of the complications which may result from 

 the lesions produced. 



The similarities and the differences in the physicochemical 

 properties of antigen, in the biologic action of the reacting 

 substances, in the nature and effects of the reactions; all 

 serve as a basis for a natural classification of infectious dis- 

 eases; but it is evident that such a classification will only 

 be of purely theoretical interest. 



Every therapeutic intervention ought to be based on the 

 knowledge of the facts which we have just reviewed, because 

 they are facts which determine successive stages in the 

 evolution of each disease caused by an antigen. A classifica- 

 tion permits us at the same time to group in a rational 

 manner therapeutic methods and to foretell the results 



