EERLICE'S SPECIFIC THERAPEUTICS 215 



bonds of the receptor atom groups and the corresponding bonds of the 

 external groups being so related structurally that they dovetail, or in 

 Emil Fischer's well-known analogy, fit each other as lock and key. The 

 extraneous substance is thus in Ehrlich's own terminology "fixed," 

 anchored or bound by the special chemoreceptor groups or the products 

 they throw out. Now what we know of the dynamics of cellular pathol- 

 ogy is summed up in Carl Weigert's generalization that the amount of 

 repair of an injured or diseased tissue is usually in excess of what is 

 required, provided the original injury is not too great. When a cell is 

 attacked by a toxin or poison the receptor atom groups will, unless im- 

 mediately overwhelmed, gradually acquire the power of throwing into 

 the blood detached portions or products of themselves — ^the antitoxins — 

 and these new side-chains float in the neighborhood of the cell, like so 

 many battleships to protect it from injury. Ehrlich compares these 

 antibodies to lightning rods which draw away the destructive elements 

 to themselves. When administered as therapeutic injections he com- 

 pares them to " charmed bullets which strike only those objects for 

 whose destruction they have been produced." This is the gist of Ehr- 

 lich's theory of immunity and its central idea of a special affinity be- 

 tween drugs and tissues has been the center of gravity of Ehrlich's life 

 work. The unusual terminology which he employs — the various toxo- 

 phores, toxoids, toxones, amboceptors, haptines, etc. — are simply so many 

 tags or labels affixed to designate complex protoplasmic products of 

 unknown composition with the action of which he has become familiar 

 through long process of experiment. The importance of these imagina- 

 tive concepts, Ehrlich insists, is in their " heuristic value." How great 

 this heuristic value is, how it has served as an inductive principle in 

 seeking the essentials through the labyrinth of accidentals, is seen in 

 such a triumph of synthesis as the Wassermann method for the sero- 

 diagnosis of specific infections. Concerning this discovery Wassermann 

 says that although the side-chain theory was for years an apple of dis- 

 cord among bacteriologists, a thing to look upon askance, yet he could 

 never have hit upon so special a test without Ehrlich's imaginative 

 picture of the mechanism of disease as a guide in his experiments.^" 

 Protected by parallel control tests with known syphilitic and non-syphi- 

 litic bloods, this mode of diagnosis is practically infallible, even in 

 ataxia and paresis. As an important step forward, it changed the whole 

 aspect of those puzzling cases of immunity from syphilis which are 

 known as Colles's law and Profeta's law. By Colles's law a syphilitic 



" " Die Seitenkettentheorie, der jahrelange Zankapfel im bakteriologischen 

 Lager, hat besonders dazu gefiihrt, Ehrlich in manchem medizinischen Kreisen 

 als ' Theoretiker ' auf dem Immunitatsgebiete zu betrachten, und den ' prak- 

 tischen' Wert der Seitenkettentheorie tiber die Achsel anzusehen. Demg^en- 

 (iber kann der Schreiber dieser Zeilen nur sagen dass man ohne die Lehren 

 Ehrlichs beispielweise niemals die Serodiagnostik der Syphilis hStte finden 

 kSnnen," A. Wassermann, Munchen. med. Wchnschr., 1909, LVI., 247. 



