372 BACTERIOLOGY. 



a suitable toxin and by employing and distributing an 

 antitoxin as a standard to test toxins by. In this way 

 smaller testing stations can make their results corre- 

 spond with those of the central station. 



In spite of the great variations in the neutralizing 

 value of a fatal dose in different toxins we do not be- 

 lieve there has been any such great difference in the 

 toxins used by the different stations for testing pur- 

 poses. Most laboratories have taken the culture fluid 

 at about the time of its greatest toxicity, and the 

 neutralizing value of a fatal dose of this toxin would 

 seldom vary more than 10 per cent, above or below the 

 standard now adopted in Germany by the government 

 testing station, this latter being presumably as close as 

 possible to that used to establish the original Behring- 

 Ehrlich unit. 



Where error has been made it has usually been by 

 taking too old culture fluids, which would cause the 

 antitoxin strength of samples tested to be estimated 

 below and not above its real value. Culture 8, which is 

 used not only by the New York Board of Health Labor- 

 atory but by many other laboratories in the United 

 States and Europe, fortunately produces on the sixth 

 to eighth day the time at which the culture is usually 

 removed a toxin which grades Ehrlich's antitoxin 

 within 5 per cent, of the strength given by him. 



We believe that by using such a bacillus we can, 

 after gaining a fuller knowledge of its characteristics, 

 obtain a toxin of a known and suitable neutralizing 

 value, and thus always correctly standardize an anti- 

 toxic serum. This is certainly true for the bacillus 

 which we have used for the past four years. Mean- 

 while, a fairly permanent preparation of a carefully 



