54 EVOLUTION OF THE INFECTIOUS DISEASES 



For the moment we can say with certainty that this natural 

 tuberculin is no more pathogenic for healthy tissues than 

 artificial tuberculin. The one and the other become patho- 

 genic only when in combination with tuberculous antibody 

 in the interior of cells. If natural tuberculin provokes the 

 formation of antibodies in excess, and if it has not been pos- 

 sible up to the present time to obtain an analogous hyper- 

 sensitization by repeated injections of artificial tuberculin, it 

 is very probably because the injections, even if often repeated, 

 do not act in the same way as the slow but steady diffusion 

 of the bacterial secretion from a tuberculous focus. We can 

 also say with certainty that it is in consequence of the action 

 of these bacterial secretions, harmless for normal tissues, that 

 antibody in excess is formed and we must necessarily con- 

 clude that normal intracellular antibody can fix tuberculin 

 in quantity strictly immunizing or, in other ivords, easily diges- 

 tible and hence not pathogenic for the cell. There is here no 

 fixation by the normal antituberculin of tuberculin "en 

 surcharge," which might be directly toxic as in the case of 

 diphtheria antitoxin and toxin. This immunizing action has 

 the effect of multiplying the normal antibody of which a 

 certain quantity remains in the sensitive cells and of which 

 the surplus passes into the circulation. Experience has 

 shown that tuberculin secreted by a tuberculous focus pene- 

 trates throughout the organism and that it provokes immu- 

 nizing reactions in every tissue, especially in those of ecto- 

 dermal origin. 



At a given moment after an incubation period, longer or 

 shorter according to the virulence of the bacteria and the 

 number of foci, all the sensitive cells of the organism especially 

 those near the infectious foci are surcharged with antituber- 

 culin. That phase of the evolution of the disease which 

 corresponds in diphtheria to immunization and recovery 

 (because the combination of toxin with an excess of antitoxin 

 is completely neutral for the organism) determines in tuber- 

 culosis the beginning of the pathologic state because the 

 compound of tuberculin and antituberculin fixed in the cells 

 is pathogenic for the cells. 



Thus for diphtheria it is the surcharge of toxin; for tuber- 



