214 INFECTION AND IMMUNITY 



possessing by chance specific affinity for a given toxin, are, by their 

 union with toxin, rendered useless for their normal physiological func- 

 tion. By the normal reparative mechanism of the body these recep- 

 tors are probably cast off and regenerated. Regenerative processes of 

 the body, however, do not, as a rule, stop at simple replacement of lost 

 elements, but, according to the hypothesis of Weigert, 1 usually tend to 



overcompensation. The receptors eliminated 

 To-jcin. by toxin absorption are not, therefore, simply 



reproduced in the same quantity in which 

 .they are lost, but are reproduced in excess of 

 > ~ Antitoxin the simple physiological needs of the cell. 

 Continuous and increasing dosage with the 

 poison, consequently, soon leads to such 

 FIG 56--TV)xiN AND excessive production of the particular re- 

 ANTITOXIN. ceptive atom-groups that the cells involved 



in the process become overstocked and cast 



them off to circulate freely in the blood. These freely circulating re- 

 ceptors atom-groups with specific affinity for the toxins used in their 

 production represent the antitoxins. These, by uniting with the 

 poison before it can reach the sensitive cells, prevent its deleterious 

 action. (Fig. 56.) 



The theory of Ehrlich, in brief, then, depends upon the assumptions 

 that toxin and antitoxin enter into chemical union, that each toxin 

 possesses a specific atom-group by means of which it is bound to a pre- 

 existing side chain of the affected cell, and that these side chains, in ac- 

 cordance with Weigert's law, under the influence of repeated toxin stimu- 

 lation, are eventually overproduced and cast off by the cell into the 

 circulation. 



It stands to reason that this theoretical conception would be vastly 

 strengthened were it possible to show that such receptors or toxin- 

 binding atom-groups actually pre-existed in the animal body, and such 

 support was indeed given by the experiments of Wassermann and Taka- 

 ki. 2 These observers succeeded in showing that tetanus toxin could be 

 rendered innocuous if, before injection into animals, it was thoroughly 

 mixed with a sufficient quantity of the fresh brain substance of guinea- 

 pigs. Similar observations were independently made by Asakawa, 3 and 



1 Weigert, Verhandl. d. Ges. Deutsch. Naturf. u. Aerzte, Frankfurt, 1896. 



2 Wassermann und Takaki, Bed. klin. Woch., 1898, 

 5 Asakawa, Cent. f. Bakt., 1898. 



