200 LECTURES ON IMMUNITY 



trasted the difference between the action of pure toxin and 

 of a mixture of toxin and antitoxin, so that there is no doubt 

 upon that point. But there is also no doubt that this dif- 

 ference may be as well explained by the presence of re- 

 action-products of toxin and antitoxin in the solution as by 

 the assumption of a different poison in the two cases. 



There is another experiment by van Calcar, 1 which is 

 cited by the many pupils of Ehrlich, who attempt to defend 

 his views, v. Calcar believed he had found that it was 

 possible by the aid of diffusion under pressure to separate 

 diphtheria poison from the accompanying "toxon"; the 

 latter, he reported, was not able to pass through a membrane 

 while the real toxin diffused. Romer 2 has repeated the 

 experiment of v. Calcar and found that it was impossible 

 to detect " the least difference in the behaviour of the origi- 

 nal diphtheria poison and of its diffusion-products." Fur- 

 thermore, he subjected the results of v. Calcar to a critical 

 examination and stated that his experiments did not war- 

 rant the conclusion that it is possible to separate toxons 

 from diphtheria-toxin. In the laboratory of Madsen, Wai- 

 bum has made a thorough investigation of v. Calcar's 

 experiment and come to the same conclusion as Romer, so 

 that there seems to be no doubt that "toxon" cannot be 

 separated from diphtheria-toxin by means of diffusion 

 under the conditions employed by v. Calcar. 



The " prototoxoid " also seems to be unproved, if we 

 subject the experimental material to a closer analysis. 

 On surveying the material published by Madsen, it struck 

 me that it had not been employed as exhaustively for the 



1 Van Calcar: Berl. klin. Wochcnschrift, No. 39 (1904). 



2 Romer: Bchrings Bcitrage z. exp. Thcrapit (1904). 



