718 PASSIVE IMMUNIZATION SERUM THERAPY 



comes dissociated to unite with body-cells and stimulate the production 

 of antitoxin. 



The mixture of toxin, and antitoxin is known as T.-A., and several 

 preparations are being used; of these, T.-A. 8 possesses the lowest 

 toxicity, and has a value equivalent to that of the standard preparation, 

 M. M. 1, while T.-A. 7 is ten times and T.-A. 6 twenty times as strong 

 in its toxic and immunizing power for man. 



Before using it in human practice, Behring very carefully tested his 

 mixtures on lower animals, and every new lot of T.-A. is carefully tested 

 by the same means to make sure that it does not contain a trace of the 

 paralyzing element of the toxin, that its toxic power is exactly determined 

 by testing it on guinea-pigs, and finally that the mixture be known, by 

 trial on horses, to be capable of producing antitoxin. Further, Behring 

 requires the testing of every new lot by his standard preparation M. M.I, 

 which has retained its toxic and immunizing properties for over a year 

 unchanged. 



The method has now been used for immunizing a large number of 

 persons, chiefly under the supervision of von Behring and his assistants. 1 

 The natural antitoxin content of the blood is determined, usually by 

 the intracutaneous method on the guinea-pig, before and after immuni- 

 zation, and has shown uniformly a considerable increase, which persists 

 over many months. 



Local and general reactions have been observed, especially in older 

 children and adults with doses intended for the new-born; this fact is 

 explained on the assumption of a specific sensitization in consequence 

 of the previous introduction of diphtheria bacilli (carriers), which latter 

 render the individuals hypersensitive to the T.-A. Reactions that are 

 regarded as non-specific have been observed in tuberculous and scrofu- 

 lous persons, and for the present von Behring prefers that the use of the 

 prophylactic in such persons, as well as in atrophic infants and infants 

 less than nine months old, be regarded as contraindicated. 



The fear expressed by some that the prophylactic is contraindicated 

 in those persons who harbor diphtheria bacilli for fear of producing the 

 disease during temporary depression of the defensive mechanism has 

 been finally dissipated as the result of practical experience. Not one 

 of the numerous bacillus-carriers that have been injected with T.-A. 

 have sickened with diphtheria. Whether or not the active immuniza- 



1 See Semaine M&licale, 1913, xxxiii, No. 18; Berl. klin. Wochenschr., 1914, 

 li, 917; Therap. Monatssch., 1913, xxvii, No. 11. 



