TUBERCULIN AND MALLEIN 177 



micro-organisms of these diseases, perhaps to the existence of 

 the same anatomical type of lesion, the tubercle, or perhaps 

 to similar inflammatory and phagocytic reactions. 



Antituberculin ? Does tuberculin in animals, tuber- 

 culous or not, treated and habituated to its effects, give rise to 

 the production of an antituberculin comparable to antitoxins 

 or even anti-endotoxins ? No; an antituberculous serum 

 comparable to antidiphtheria or even antiplague sera does not 

 exist, in spite of all efforts to discover it. Tuberculin in 

 tuberculous subjects excites the production of certain reaction- 

 or anti-bodies, but no true antitoxin. No treated individual 

 has ever furnished a serum capable of neutralizing tuberculin 

 either in vitro or in vivo, but serum of this kind can produce 

 precipitates and clumps in a suspension of bacilli ; this action 

 is, however, inconstant and of little value in medicine. 



Wasserman and Bruck have given the name of antituberculin 

 to the reaction products which fix themselves on tuberculin as 

 anti-bodies do on antigens (v. Chap. X.). The interpretation 

 of these experiments is a question of some delicacy, and we 

 shall see how doubtful are the relations between the presence 

 of antibodies and the existence of an immunity, e.g., a 

 resistance in the case of tuberculous individuals. 



Habituation to Tuberculin. By careful, repeated 

 injections the tuberculous subject may be made to protect 

 himself against the fatal action of tuberculin, and to enjoy a 

 general improvement in his condition, without stopping the 

 progress of his tuberculosis. Guinea-pigs may be made to 

 support fifty lethal doses, yet their lesions progress in the 

 ordinary way or even more quickly than usual. It is not 

 yet well known what are the relations between the physiological 

 action of tuberculin and the progress of a chronic tuberculosis. 



This habituation has been called immunity to tuberculin. It 

 is not, however, an immunity or even a resistance to tuberculosis. 

 It does not appear on repeated injections of equal small doses 

 of tuberculin ; in this case, the febrile reaction, which was 

 absent at first, finally appears and becomes severe. The fever 

 remains absent when one proceeds by increasing doses (always 



