V 



ous experiments on guinea-pigs of 250 Grs. weight, the 

 minimal lethal dose was found to be 0.0015 i. e. guinea- 

 pigs of the above weight were killed with certainty within 

 46 days by the injection of this amount of toxin. 



Besides this the value of Lf and L were found 

 by means of Ehrlich's test serum to be: Lf = 0.2 and L 

 ca. 0.05. 



The determination of L for this toxin was much 

 more difficult than for any other previously examined, 

 therefore the value 0.05 must be regarded as rather 

 arbitrary. 



In considering the above values for minimal lethal 

 dose, Lf and L , it will be noticed that the Lf is four 

 times the L and that the Lf and L respectively contain 

 183 and 33 minimal lethal doses. These constants are 

 entirely different to any that have been determined be- 

 fore for any other toxin. 



For making the "spectrum" in the manner directed 

 by Ehrlich, by partial saturation of the given quantity 

 of toxin with antitoxin, 0.1 Cc. was chosen as the most 

 convenient quantity of toxin for the purpose. As anti- 

 toxins the following were used: 1) a real antitoxin i. e. 

 Ehrlich's test serum and 2) the normal serum from a 

 non-immunised horse. 



Much trouble has been taken to find out the history 

 of this horse, so that it should be as far as possible 

 quite certain that it had never been in contact with 

 Diphtheria or been used for the production of diph- 

 theria antitoxin. 



The results obtained are represented by two curves, 

 the dotted line indicates the curve obtained by the use 

 of the test serum and the unbroken line that of the 

 serum from the normal horse. 



It will be seen that there is a very striking resem- 



