142 Immunity 



Different standards for measuring the strength of the 

 tetanus toxin and different definitions of the unit of measure- 

 ment are given in different countries, so that great confusion 

 and dissatisfaction were experienced until a special committee 

 of the Society of American Bacteriologists met in New York, 

 Dec. 27 and 28, 1906, and in collaboration with the United 

 States Public Health and Marine Hospital Service, Hygienic 

 Laboratory, formulated a standard unit which has become 

 the legal unit of measurment for the United States. It is 

 thus denned: 



" The immunity unit for measuring the strength of tetanus 

 antitoxin shall be ten times the least quantity of antitetanic 

 serum necessary to save the life of a 35o-grain guinea-pig 

 for ninety-six hours against the official test dose of a standard 

 toxin furnished by the Hygienic Laboratory of the Public 

 Health and Marine Hospital Service." The unit is thus 

 officially defined, Oct. 25, 1907, in Treasury Circular, No. 61. 



Testing tetanus antitoxic serums immediately became 

 a matter of great simplicity. The governmental laboratory 

 furnishes the "test toxin" whose strength is guaranteed, 

 and what follows is a simple matter of dilution, admixture 

 with the serum to be tested, and injection animals that are 

 carefully observed for a few days. 



The entire subject, historical, theoretical, and practical, 

 is treated in Bulletin, No. 43, 1908, of the Hygienic Labora- 

 tory upon "The Standardization of Tetanus Antitoxin," 

 by Rosenau and Anderson. 



3. Antivenene or Anti-venomous Serum. This was 

 discovered by Phisalix and Bertrand* and made practical 

 for therapeutic purposes by Calmette.t Calmette found 

 that cobra venom contained two principles, one of which, 

 labile in nature and readily destroyed by heat, was destruc- 

 tive in action upon the tissues with which it came into direct 

 contact, the other, stable in nature, was death-dealing 

 through its action upon the respiratory centers. By heat- 

 ing the venoms and thus destroying the irritative principle, 

 he was able to immunize animals against the other, which 

 he looked upon as the important element of the venom. 

 The immunized animals furnished an anti-serum, which 



*"Compt. rendu de 1'Acad. des Sciences de Paris," Feb. 5, 1894, 

 Tome cxvm, p. 356. 



t "Compt. rendu de la Soc. de Biol. de Paris," 10 Series, Tome i, 

 p. 1 20, Feb. 10, 1904. 



