PIRQUET REACTION. 605 



in a few weeks. The best time for a single obser- 

 vation is 48 hours after the vaccination. 



(d) Secondary reaction: In cases giving a neg- 

 ative reaction a second test may be followed by a 

 positive reaction. In this case, the first vaccina- 

 tion site may show a slight reddening. 



The cutaneous reaction is a very delicate one yi of . 



i .the Reaction. 



and many cases oi healed tuberculosis give a posi- 

 tive reaction. Since most adults, according to 

 autopsy findings, have healed foci of tuberculosis 

 the reaction as an indication of active lesions is 

 of value only in children below the age of puberty. 



Various modifications of the v. Pirquet reaction 

 have been devised but cannot be discussed here. 



Calmette proposed the instillation of tuberculin 

 into the conjunctival sac as a diagnostic procedure Reaction 

 in tuberculosis. In negative cases this is followed 

 by only a slight reddening. In positive reactions 

 a more or less severe conjunctivitis follows. The 

 reaction has not become popular owing to the pos- 

 sibility of danger to the eye. 



The original unfavorable results which were ob- 

 tained in the therapeutic administration of tuber- 

 culin are referred by Koch, Petruschky and others 

 to improper selection of patients. Those in a feb- 

 rile condition and those in whom destruction of 

 tissue is advanced are not suited for the treatment, 

 and in them little or nothing is to be hoped from 

 the administration of tuberculin. Its curative value 

 is supposed to depend on the local inflammatory 

 reaction which it causes around tuberculous foci, 

 and perhaps also on the necrosis which Koch claims 

 is caused in the tubercles themselves. It must be the 

 object during the whole course of treatment to ad- 

 minister the toxin in such doses that a moderate 



