56 EVOLUTION OF THE INFECTIOUS DISEASES 



Another point : Artificial tuberculin applied to the skin or 

 the eye of the first guinea-pig will not evoke a reaction until 

 after the tubercle has been established and has begun to 

 heal and this test can thereafter be elicited throughout the 

 life of this guinea-pig unless at some time the animal is over- 

 whelmed by a "miliary tuberculosis." 



In a normal pig, a "tubercle" does not appear until the 

 production of anti tuberculin in excess. This antituberculin 

 in excess remains in all the cells of the guinea-pig " en sur- 

 charge" and can fix to these cells in equal quantity its own 

 "anti" that is to say, tuberculin whether artificial or natural 

 whenever injected. And in this way is explained the local 

 and general reactions of the second injections. That this 

 second dose produces only a temporary reaction and that the 

 animal ultimately recovers (showing immunity) is explained 

 by the persistence of antituberculin. 



However, when the available antituberculin is less than the 

 new dose of tuberculin, the organism will be overwhelmed, 

 local skin and eye reactions can be no longer produced and 

 the animal will die. 



Let us now return to the tuberculous focus. The bacteria 

 of this focus secrete tuberculin which spreads to the sur- 

 rounding tissues and causes in the cells a multiplication of 

 antibodies. These cells then become capable of fixing larger 

 and larger quantities of tuberculin without pathologic mani- 

 festation up to a certain limit (greater and greater immunity 

 to tuberculin). When this limit is passed the quantity of 

 antituberculin en surcharge forms with tuberculin pathogenic 

 compounds and it is only then that the lesion appears. 



The first phase of the infection, therefore, corresponds 

 to the incubation period, the second phase to the period of 

 disease. It is thus evident that from the beginning of the 

 infection, the evolution of a tuberculous focus will be deter- 

 mined by the three following factors : 



1. The quantity of tuberculin secreted by the bacteria. 



2. The multiplication of the antibodies in the cells which 

 surround the focus. 



3. The quantity of tuberculin which is fixed by the cells 

 and which will diffuse into the general economy. 



