ALLERGIC REACTIONS 311 



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 already 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 disintegration 

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

 is readily accounted for, if we remember that the parenteral intro- 

 duction of foreign proteins (in the present instance of bacterial pro- 

 teins) leads to the formation of corresponding antibodies, and that 

 as a consequence of the interaction between the two groups of sub- 

 stances, in the presence of complement, toxic bodies (anaphylatoxins) 

 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 

 to those observed in the guinea-pig. The subcutaneous injection 

 of the non-tubercular individual with small doses of tuberculin will 

 thus produce no deleterious consequences whatever, while in the 

 tubercular subject the same dose causes the well-known general 

 response by headache, muscle pains, and fever, besides the local 

 inflammatory reaction at the site of the injection. In cases where 

 the tubercular lesion is superficially located and can be directly 



