PRODUCTION OF TETANUS ANTITOXIN 



235 



the official test dose of a standard toxin. This test dose consists of 100 

 minimal lethal doses of a precipitated and dried toxin, tested out 

 against 350-gram pigs, and preserved in the Hygienic Laboratory, 

 from where it is sent to various antitoxin plants for the purpose of secur- 

 ing a uniform method and unit of standardization. 



In standardizing tetanus antitoxin, the L+ dose of toxin is em- 

 ployed. A standard toxin and an antitoxin, arbitrary in their first 

 establishment, are preserved in the Hygienic Laboratory, and are kept 

 constant by making frequent tests one against the other. In determin- 

 ing the L_f. dose, increasing amounts of toxin are mixed with a constant 

 amount of antitoxin equal to one-tenth of an immunity unit, and in- 

 jected into 350-gram pigs. The L+ dose must contain just enough 

 toxin to neutralize this amount of antitoxin and kill a pig in four days. 

 This L + dose of toxin is sent out by the Hygienic Laboratory to those 

 interested, commercially or otherwise, in the manufacture of antitoxin 

 for purposes of standardization. 



For determining the strength of an unknown serum a large number 

 of mixtures are made, each containing the L + doses of the toxin and 

 increasing quantities of antitoxin. The measurements are made with 

 accurate volumetric pipets, and the total volume brought up to 4 c.c. 

 with sterile salt solution in order to equalize concentration and pressure. 

 The mixtures are allowed to stand at room temperature for an hour, and 

 are then injected subcutaneously into 350-gram pigs. This method 

 of titrating the antitoxin is shown in the following example from Rosenau 

 and Anderson: 



TABLE 2. METHOD OF TITRATING TETANUS ANTITOXIN 



In this series the animal receiving 0.0015 c.c. of antitoxin died in 

 approximately four days; this amount of serum, therefore, represents 

 of one unit. 



