TOXINS AND ANTITOXINS 279 



At the present time it is possible to procure what is regarded 

 as an efficient antistreptococciis antitoxin. It may be used for 

 temporary protection lasting two or three weeks or as a therapeutic 

 agent. 



Measurement op Antitoxin and Toxin. — The unit of antitoxin 

 established by the federal government is described as follows : 

 "One unit of antitoxin is the smallest amount of antitoxin which 

 neutralizes 50 skin test doses of scarlatinal streptococcus toxin." 

 (Zinsser and Bayne- Jones, 1939, p. 300.) Wadsworth* states that 

 the skin test dose of toxin is "the least quantity of toxin, which, 

 when injected intracutaneously into persons known to be susceptible 

 to the toxin, will induce a reaction equal to that induced on the 

 same persons at the same time by the injection of a skin test dose 

 of the standard toxin supplied by the U. S. National Institute of 

 Health (Hygienic Laboratory)." This dose is contained in a 

 volume of 0.1 c.c. A positive reaction appears as a pink or red 

 area at least one centimeter in diameter usually within six to 

 twelve hours and begins to fade after about twenty-four hours. 

 It is usually read after twenty-two to twenty-four hours. 



Schultz and Charlton Blanching Test. — In 1918 Schultz and 

 Charlton reported that the serum of those convalescing from 

 scarlet fever wdll blanch the rash of scarlet fever when injected 

 intradermally. Their results have been extensively confirmed. 

 Toomey and Nourse (1924) state that it is necessary to use 

 pooled convalescent sera to obtain an efficiency of approximately 

 100 per cent in diagnosis. They recommend the intradermal in- 

 jection of one cubic centimeter of serum and that the test be 

 read not earlier than eight and preferably not until after twenty- 

 four hours. Commercial antitoxin for use in the blanching test 

 is equally satisfactory. 



Potency of Convalescent Serum. — The question arises not in- 

 frequently as to the relative value of convalescent serum and com- 

 mercial antitoxin as a diagnostic prophylactic or therapeutic 

 agent. The interesting work of Rhoads and Gasul (1934) bears 

 directly upon this question. They call attention to the meager- 

 ness of reports of the use of convalescent serimi for the protec- 

 tion of contacts since its therapeutic value was demonstrated by 



♦Wadsworth: J. Immunol. 31: 255, 1931. 



