6 Ehrlich's Theory 



measurable quantities in vitro, more rapidly in concentrated solutions, 

 the union being retarded by cold, hastened by heat. In other words, 

 the union took place in a manner similar to that observed with regard 

 to known chemical bodies. 



Ehrlich concluded that " the power of toxins to combine with 

 antibodies must depend upon a specific atom-group in the toxin- 

 complex possessing a maximal specific relation to definite atom-groups 

 of the antitoxin-complex, so that it rapidly unites therewith, like a 

 lock and key," a figure borrowed from Emil Fischer in describing the 

 action of specific ferments. 



Ehrlich's theory (1897) had its origin in an hypothesis advanced 

 by Weigert in 1896, to the effect that a condition of physiological 

 equilibrium is maintained in the body by virtue of mutually restraining 

 influences exerted upon each other by the cells which compose it. 

 Assuming that a cell or a group of cells are destroyed through some 

 agency, the equilibrium is upset, an element of restraint will be 

 removed, and there will be an overproduction, comparable to the 

 compensating hyperplasia observed when an organ is removed, say a 

 kidney, a double function being thrown upon the one which remains. 

 According to Weigert, there is always hypercompensation where there 

 has been destruction of cells. The above conception is narrowed down 

 by Ehrlich to what takes place in a single cell. 



The processes which lead to the formation of antibodies such as 

 antitoxins are, according to Ehrlich, essentially similar to those taking 

 place normally in the process of assimilation. We now know that 

 normal serum contains a number of antibodies having similar actions 

 to those artificially produced as a result of immunization with this or 

 that substance, we know of normal agglutinins, haemolysins, bacterio- 

 lysins, antitoxins, antiferments, etc., all of which go to prove the 

 correctness of Ehrlich's views in this respect. In normal processes of 

 assimilation food substances are taken up by the cells with whose 

 substance they enter into chemical combination. That a toxin also 

 enters into chemical union with certain cells of the body was 

 indicated by the experiments of Wassermann, who found that when 

 he mixed tetanus toxin with the brain substance of the susceptible 

 guinea-pig, that the mixture was no longer toxic for the guinea-pig. 

 There was evidently a special affinity between the brain substance and 

 the toxin, for the reason that emulsions of other guinea-pig organs 

 when brought in contact with tetanus toxin exerted no such effect. 

 It would appear from this experiment that a toxin may have a special 



