THE SCHICK TEST FOR NATURAL DIPHTHERIA ANTITOXIN 229 



the injected toxin is neutralized and no reaction follows; if, however, 

 the person does not have antitoxin in the body fluids, the injected toxin 

 acts as an irritant to the skin, producing in twenty-four to forty-eight 

 hours a small area of redness and edema. A positive reaction indicates 

 that the person does not possess natural antitoxin in his blood, and there- 

 fore that he is susceptible to diphtheria; a negative reaction indicates 

 that natural antitoxin is present and that he is, in all probability, immune 

 to diphtheria. In the presence of exposure to diphtheria, persons reacting 

 positively to the toxin skin test should receive a prophylactic dose of 

 antitoxin, while those reacting negatively may with safety be spared 

 the injection. 



FIG. 68. METHOD OF ADMINISTERING AN INTRADERMAL INJECTION OP DIPHTHERIA 



TOXIN IN THE SCHICK TEST. 



The skin has been cleansed with alcohol and pinched up between the thumb and 

 index-finger of the left hand; the needle (No. 26) has been entered into the epidermis 

 and 0.1 c.c. of fluid injected. Note the anemic area indicating that the injection 

 has been intradermic. The same technic is employed in conducting the luetin test. 



It will be understood, therefore, that the diphtheria toxin skin reac- 

 tion is purely an inflammatory reaction due to the fact that the toxin in the 

 skin excites inflammation if not neutralized with diphtheria antitoxin ; it 

 is not an anaphylactic reaction, as the tuberculin and luetin reactions. 



The amount of toxin to be injected must be determined beforehand 



