ALLERGIC REACTIONS 331 



hence sensitized organism to the parenteral reintroduction of the 

 corresponding antigen. Among the infectious diseases such reactions 

 have been notably studied in connection with tuberculosis, but are 

 evidently destined to play an important role in the diagnosis of 

 other diseases as well. In the present work we shall confine our 

 attention to the tubercular test and the luetin reaction in their 

 relation to the diagnosis of tuberculosis and syphilis respectively. 



The Tuberculin Test. It will be recalled that the tubercular guinea- 

 pig responds quite differently to the introduction of living tubercle 

 bacilli than does the normal animal. For whereas in the latter a 

 local reaction occurs only after from ten to fourteen days, definite 

 changes can be detected in the former within twenty-four to 

 forty-eight hours. But while in the primarily non-tubercular 

 animal the local lesion then remains active to the end, local recovery 

 occurs in the reinjected tubercular pig. If an emulsion of dead 

 organisms (tuberculin) be used instead, as much as 0.5 gram may 

 be injected, intraperitoneally even, in the case of the normal animal 

 without producing any deleterious results, while similar treatment 

 of the tubercular guinea-pig would lead to a fatal ending. If the 

 injection is made subcutaneously, and the dose is chosen sufficiently 

 small as not to kill, a severe local reaction will result, as in the first 

 instance, where living organisms were used, and incidentally it will 

 be observed that in the tubercular in contradistinction to the non- 

 tubercular animal, temporarily at least, certain general symptoms 

 of illness develop, of which a rise in temperature is the most striking 

 and the most constant. Evidently the primary inoculation, while 

 increasing the resistance of the animal to subsequent infection with 

 the organism in question (immunity), has called forth a general, 

 increased susceptibility to the action of its products of disintegra- 

 tion (anaphylaxis). According to v. Pirquet this difference in 

 response is readily accounted for, if we remember that the parenteral 

 introduction of foreign proteins (in the present instance of bac- 

 terial proteins) leads to the formation of corresponding antibodies, 

 and that as a consequence of the interaction between the two groups 

 of substances, in the presence of complement, toxic bodies (ana- 

 phylatoxins) are formed which may then produce symptoms of 

 variable nature, according to the character of the tissues which are 

 susceptible to their action. 



In man results have been obtained which are perfectly analogous 



