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Dr. Paul Ehrlich. 



group. In the formation of antitoxine the toxophore group of the 

 toxine molecule is, on the contrary, of absolutely no moment. But 

 the toxoid modifications of the toxines, in which the haptophore 

 group of the toxine is retained, while its toxophore group has ceased 

 to be active, possess the property of producing antitoxines. 



Indeed, in some cases of extremely susceptible animals, immunity 

 can only be attained by means of the toxoids, and not by the too 

 strongly acting toxines. The toxoids are certainly able to cause the 

 production of antitoxines. To quote an example, it is hardly possible 

 in an animal, which, like the guinea-pig, has all the tetanophile groups 

 confined to the cells of the central nervous system, to produce im- 

 munity by means of the unaltered tetanus toxine, whereas this is 

 attained with extraordinary rapidity and ease by means of its toxoids. 



The symptoms of illness due to the action of the toxophore group, 

 therefore, play no part in the production of antitoxine. On the con- 

 trary, we may consider that the severe symptoms, which indicate 

 injury to the cell-life, disturb the regenerative functions, and thus 

 hinder or entirely frustrate the course of the immunisation process. I 

 have from the first adopted this view, and it was simply a misunder- 

 standing when Knorr, who has been all too soon taken from the field 

 of his labours, affirmed that, according to my theory, sickness of the 

 cell constituted the necessary condition precedent to the new forma- 

 tion and pushing-off of side-chains. 



If I am not altogether deceived, the toxoids, where it is a question 

 of producing an active immunisation (and this will always be the case 

 when the immunisation concerns human beings), are destined to play 

 an important role in practical medicine. 



In their theoretical relations the toxoids are also of far-reaching 

 interest, in that they provide a transition to that immunisation which 

 can be called forth by substances which would a primi be considered 

 entirely devoid of toxic character, and which are sometimes, like the 

 autochthonous ferments {i.e., those normally present in blood), pro- 

 ducts of normal cell-life, and in some cases food-stuffs proper. Thus 

 Dr. Morgenroth, workmg in my laboratory, has proved that the rennet 

 ferment, if introduced in great quantities into the organism, behaves 

 exactly like a real toxine, in that it causes the production of a typical 

 anti-rennet, which up to a certain limit accumulates in proportionally 

 sjreater quantity, the greater the injected doses. Here, however, we 

 have to do with processes which are altogether mthin the region 

 of the normal, as is most clearly shown in certain animals, e.g., the 

 horse, in the blood serum of which there is normally present a 

 quantity of anti-rennet, equal to that attained in the goat only after a 

 systematic immunisation carried on for months. The rennet ferment 

 present naturally in the body of the horse is the cause of this great 

 formation of anti-rennet. According to Bordet's experiments, if 



