224 CLINICAL BACTERIOLOGY. 



toxin added, and then there must be present, besides, a sim- 

 ple toxin-unit in order to attain L + and to cause the death 

 of the animal. D corresponds here to the epitoxoid-units 

 plus I toxin-unit. Every normal toxin-bouillon contains 

 the three toxoids. Their relations may be represented as 

 follows : Diphtheria-bouillon = x-toxoids (protoxoids and 

 syntoxoids) -f- y-toxin -f- z-epitoxoid. L , then, = x- 

 toxoid saturated -|- y-toxin saturated -\- z-epitoxoid satu- 

 rated. To determine the equivalent of in toxin, it is only 

 necessary to know the number of lethal doses present in 

 L . L + then corresponds with the formula : x-toxoid 

 saturated -{- (y -f- z) toxin saturated + 1 toxin free -f- z-epi- 

 toxoid free. The number of epitoxoids /? equals, as has 

 been seen, D 1, but only in the event of the bouillon 

 being constituted exclusively of toxin and epitoxoid. If 

 additional toxoids are present, then /3 expresses a relative 

 value, and is, therefore, designated by Ehrlich as a function 

 of /?, thus, F (/?). The formula for the toxin-bouillon may, 

 therefore, be expressed as follows : x-toxoids -{- toxin -|- 

 F (/5) epitoxoid. 



For the majority of diphtheria-poisons it may be shown 

 by addition of the simple immunity-unit that they originally 

 contained the required 100 doses of toxin. The attenua- 

 tion is effected gradually according to the principle of thirds 

 or halves. Of three toxin-molecules two are converted 

 into toxoids, or 1 toxin is converted into equal parts of 

 toxoids and toxin. It appears that in this process of de- 

 composition in the cold no epitoxoid which always occurs 

 in cultures maintained at a temperature of 37 C. (98.6 F.) 

 is formed, but only protoxoids and syntoxoids. In the 

 study of an especially active toxin immediately after its 

 acquisition Ehrlich obtained the following figures : L + = 

 100 doses of toxin ; L = 50 doses of toxin. The toxin, 

 thus, was of half strength, and the figures obtained had, 

 therefore, to be multiplied by 2. The value of L+, then, 

 equaled 200, and the formula for the bouillon was as 

 follows : 50 toxoids -f- 50 toxin -f 100 epitoxoids. As a re- 

 sult of this demonstration that the antitoxin-unit saturates 

 200 toxin-equivalents, that the poison itself is attenuated 

 dichotomously, it was possible without difficulty to explain 

 the previously mysterious manifestation that with freshly 

 prepared toxins frequently just 100 toxin-equivalents are 

 neutralized by the immunity-unit. 



