60 EVOLUTION OF THE INFECTIOUS DISEASES 



its quantity increases up to the fiftieth or eightieth day, falls 

 and increases again at about the ninetieth day and disappears 

 completely some few days before death. Thus the disease 

 develops parallel to the production of antituberculin. The 

 temporary disappearances of antituberculin from the blood 

 are the consequence of the limitation of the bacterial secre- 

 tions to the tissues which surround the infectious foci because 

 of antituberculin in excess and as soon as this excess dis- 

 appears from the circulation the same process begins again 

 if not finally stopped by the death of the animal. The 

 extreme susceptibility of the guinea-pig for tuberculosis 

 probably arises from the almost absolute incapacity of this 

 animal to digest Koch's bacillus and to produce antituber- 

 culin. 



Such are the general principles which determine the evolu- 

 tion of pathogenicity of tuberculosis in so far as experiments 

 and clinical observations permit us to formulate them. They 

 may be summarized in a few lines : 



1. Infection is followed by an incubation period during 

 which the digestive attack of the bacterial secretions and of 

 the bacteria themselves results in the production of anti- 

 tuberculin and antibacillin. 



2. The period of disease begins at the moment when 

 intracellular antituberculin in excess has fixed a sufficient 

 quantity of tuberculin so that the compound of tuberculin 

 with antituberculin which is fixed in the cell can become 

 pathogenic (undigestible) for the cells themselves. 



3. Antibacillin aids in the destruction of the bacteria 

 which are multiplied in the organism. 



4. The different phases of the evolution of the disease are 

 determined on the one hand by the number and the stage of 

 development of the tuberculous foci (that is to say by reac- 

 tions successively immunizing and pathogenic between 

 tuberculin and antituberculin) : on the other hand by the 

 reactions of the antituberculin with the bacteria. During 

 this disease period pathologic impulses which follow one 

 another at longer or shorter intervals and characterized by 

 fever, lassitude, sweats, etc., are provoked by the local or 

 general rupture of the antituberculin blockade. In case 



