ANTITOXINS 41 



nation. However, recent investigations make it 

 probable that the affinity of adsorption is similar 

 to a true chemical affinity, in that both are elective. 

 It is possible, therefore, that the existence of strict 

 specificity may still be fqund entirely compatible 

 with the adsorption theory. 



Antitoxin in the Blood of Normal Individuals: 

 The Schick Test. Schick 1 has devised a method 

 by means of which small amounts of diphtheria 

 antitoxin in the blood may be very easily detected. 

 The reaction depends on the local irritant effect of 

 minute quantities of diphtheria toxin when injected 

 intracutaneously. If there is less than -^ of a unit 

 of antitoxin per cc. of blood a local reaction occurs 

 in twenty-four to thirty-six hours and is character- 

 ized by an area of redness and slight infiltration 

 which persists for seven to ten days and on fading 

 shows a superficial scaling and a persistent brownish 

 pigmentation. The toxin to be injected is diluted 

 so that ^V of a M. L. D. 2 for a 250-gram guinea pig 

 is contained in o.i cc. and the injection made on 

 the flexor surface of the forearm. In order to guard 

 against pseudo reactions, a control injection is 

 sometimes necessary. A heated toxin is then used 

 and the injection made in the other arm. If the 

 pseudo reaction which appears on the first arm is 

 caused by products of the growth of the diphtheria 



1 Munch, med. Woch., 1913. Vol. lx., p. 2608. 



2 M. L. D. = minimum lethal dose. 



