SPECIFIC BACTERL\L REACTIONS 191 



Schick's Diphtheria Toxin Skin Reaction 



This test, which promises to be of great practical 

 importance, has recently been studied in this country 

 by Veeder (Am. Jour, Dis, Child,, 1914, viii, 154- 

 162). The technic is similar to that of the Noguchi 

 luetin reaction, and consists of the intracutaneous in- 

 jection of an amount of diphtheria toxin equal to 1-50 

 of the lethal dose for a 250-gramme guinea-pig. This is 

 so diluted that the amount of toxin is contained in 0.1 

 c.c. of fluid. A positive reaction is characterized by an 

 area of redness and swelling within 24 or 48 hours, 

 and indicates the absence of antitoxin in the blood. 

 A negative result, on the other hand, is evidence that 

 the individual is well supplied with diphtheria anti- 

 toxin. By actual test it has been found that in the case 

 of a negative result the individual tested possesses at 

 least 0.031 unit of antitoxin per cubic centimetre of 

 blood, which is considered sufficient to protect him 

 from an ordinary attack of diphtheria. 



The practical importance of the test lies in its 

 use as a preliminary indicator of the necessity of pro- 

 tective injections of antitoxin in persons exposed to 

 diphtheria. It is argued that those giving negative 

 reactions already possess in the blood sufficient anti- 

 toxin for protective purposes, and therefore require 

 no prophylactic injection. Those giving positive reac- 

 tions, on the other hand, possess insufficient antitoxin, 



