Ill 



hiemolysis ot 50, 25, 20% etc. 10 cc. of these dilutions 

 were put into test tubes similar to those used in the 

 experiments. With these fluids of different shades in 

 test tubes, the tubes under experiment were compared, 

 and it was thus shown, how many of the red blood 

 corpuscles had been dissolved. The mixtures of toxin 

 which had yielded the same degree of hiemolysis, were 

 considered to have an equal amount of toxicity. In some 

 cases, for instance in experiments with toxin and anti- 

 toxin where the active toxin was the same, the same 

 toxicity corresponded to the same amount of free toxin 

 pr. cc. In these experiments we have taken into consi- 

 deration that the amount of fluid varied in the different 

 quantities of mixture of toxin added. 



In the first experiments the hrcmolysed percentage 

 of blood corpuscles was not determined. We confined 

 ourselves to show the amounts of these different doses 

 of toxin, which had brought about the same degree of 

 haemolysis, without trying to determining the absolute 

 amount of this. 



We must not forget to mention that after a few days 

 the scale of colours must be renewed, because the 

 blood turns violet and is therefore useless for purposes 

 of comparison. 



Most of our experiments are carried out by tetano- 

 hjsin. This was prepared 2 years ago by a culture of 

 Bacillus tetani, kindly sent us by Geheimrath Ehrlich. 

 Several broth cultures of this microbe were mixed to- 

 gether and precipitated in the usual way with ammo- 

 nium sulphate. During these two years, it was found 

 that this toxin got weaker and weaker. The antitoxin 

 used was kindly presented to us by Dr. Libbertz, Farb- 

 werke Meister, Lucius & Bri'ming, Hochst a/m. The 

 normal serum which we used was usually prepared 



