440 INFECTION AND RESISTANCE 



that certain cells of the tuberculous foci (those situated just below 

 the periphery and already affected by the tubercle toxin, though still 

 resistant) were possessed of an increased receptor apparatus for the 

 tubercle antigen. For this reason the injected tuberculin was con- 

 centrated in these foci, attracted out of the circulation by the in- 

 creased avidity of these cells, the consequence being increased ac- 

 tivity of the lesions and systemic symptoms. The tuberculin reac- 

 tion, according to these writers, therefore, would be caused by the 

 union of the tuberculin with the "sessile receptors" upon the diseased 

 tissues a point of view which would specify the diseased tissues and 

 their products as the sources from which emanated the toxic factors 

 inciting the systemic symptoms. 



The theories of Koch and of Babes do not, as Meyer points out, 

 explain the frequent absence of the tuberculin reaction in very ad- 

 vanced cases of human tuberculosis, as contrasted with its frequency 

 and regularity in the earlier cases. For, according to both of these 

 views, the more severe the existing lesions the more actively would 

 the injected tuberculin initiate tissue necrosis and consequent symp- 

 toms. The theory of Wassermann and Bruck avoids this objection 

 since it presupposes the acceptance of Ehrlich's view that the in- 

 creased receptor apparatus is present and free only in those cells in 

 which necrotic destruction has not yet set in. In the necrotic areas 

 the receptor apparatus is already saturated or satisfied as to its 

 affinities, and extensive areas of necrosis, therefore, are unaffected 

 by contact with further quantities of tuberculin. 



All of these theories, however, inasmuch as they refer the tubercu- 

 lin reaction to alterations taking place in more or less active lesions, 

 are unable to account for the occurrence of the reaction in persons 

 in whom healed foci only are present, and are entirely inconsistent 

 with the facts we now possess regarding the cutaneous and ophthal- 

 mic tests in which the reactions occur in previously healthy tissues. 



These facts practically exclude the acceptation of any theories 

 which regard the tuberculous focus as the sole source of the reaction. 

 We may still accept the Koch or Wassermann views to explain local 

 swellings and other changes in infected lymph-nodes or other lesions, 

 but we must assume in addition to this a generalized hypersuscepti- 

 bility at least analogous to the phenomena of anaphylaxis. 



This ability of previously healthy tissues, remote from any center 

 of tuberculous infection, to react to the application of tuberculin 

 was discovered by von Pirquet 38 in the development of his skin 

 reaction, and by Calmette 39 and Wolff-Eisner 40 in their work upon 



38 v. Pirquet. Berl klin. Woch., No. 20, p. 644, and No. 22, p. 699, 1907; 

 also "Klinische Studien iiber Vaccination," Deuticke, Wien, 1907. 



39 Calmette. C. R. de I'Acad. des Sciences, June, 1907. 



40 Wolff-Eisner. Berl. klin. Woch., 1907, p. 1052. Discussion of paper 

 by Citron. 



