XI. ACTIVE IMMUNITY AND OVERNEUTRALIZED 

 DIPHTHERIA TOXINS. 1 



By Dr. JULES REHNS. 



INSTEAD of following the classical method of immunizing against 

 diphtheria, namely, by inoculating the toxin in gradually increasing 

 doses, a number of workers have attempted to produce immunity 

 by inoculating, either from the outset or during the course of the 

 immunizing process, mixtures in which the toxin was partly, wholly, 

 or over neutralized. It will at once be realized that these methods, 

 with which the names Babes, Pavlovsky, Arloing, Madsen, and Kretz 

 are principally associated, possess an entirely different significance. 



Under the direction of Professor Ehrlich I have tried to see whether 

 active immunity could be conferred upon a given normal organism by 

 the injection of increasing doses of diphtheria toxin mixed with one 

 or more times its equivalent of antitoxin. 



Rabbits weighing about 2000 grams were used and these were 

 injected with mixtures composed of a toxin L and the Standard 

 Serum of the Institute. 



The constants of this poison, determined according to the clas- 

 sical methods devised by Ehrlich were as follows: 



(1) The amount of poison which just corresponded to an immu- 

 nizing unit, i.e., the limit of no action whatever, 



L =0.3 cc. 



(2) The amount of poison which, mixed with one immunizing 

 unit of serum, was just sufficient to kill the animal, the so-called 



Lf dose, 



L t =0.45 cc. 



(3) The fatal dose for a rabbit weighing about 2000 grams, death 

 occurring in four days: 



This was about 0.01. 



1 Reprinted from Compt. rend, de la Soc. de Biologic, 1901, page 141. 



143 



