Antidiphtheric Serum. 



^5 



quantity of serum rather than the number of units of antitoxin 

 which was efficacious. He drew the following conclusions : 



The curative effect of the serum does not depend exclusively 

 on the number of antitoxic units present. 



The ordinary method of titrating antitoxin is not sufficient to 

 determine the value of the serum. 



We have investigated the same subject with results which do 

 not agree with those of the above-named authors. In our experi- 

 ments we infected the guinea pigs with three different strains of 

 the diphtheria bacillus. We compared sera of the following unit 

 contents : One of 200 units with one of 1000 units; one of 600 

 units with one of 1300 units ; one of 600 units with one of 335 

 units, also with one of 200 units. The last three sera were obtained 

 from the same horse during the course of immunization. 



In both the preventive and curative experiments, we were unable 

 to detect any protective substances which are not measured in the 

 present method of standardizing antitoxin. 



From the results obtained in the comparison of the antitoxic 

 contents of sera we draw the following conclusions : 



The therapeutic value of the serum depends upon the antitoxic 

 content. 



The present method of standardizing an antitoxic serum ac- 

 curately measures its therapeutic value. 



