32 THE PROTEOMORPHIC THEORY AND THE NEW MEDICINE 



immune bodies. But the thermostable immune body is specific, 

 in the sense that it is evoked in response to a specific protein or 

 toxin (called an antigen), and is antidotal to the particular antigen 

 that evokes it alone. A bacteriolysin, for example, evoked in 

 response to the typhoid bacillus will not destroy the tetanus 

 bacillus. 



The validity of the conceptions associated with these terms is 

 not to be questioned. Multitudes of experiments have shown 

 that the terms "complement" and "immune body," and the ideas 

 associated with them, are compatible with observable phenomena 

 of the bacteriological world. The assumption that active comple- 

 ment must be present in order that immune body may be linked 

 with the toxic agent to neutralize it, finds support in such prac- 

 tical work as Widal's agglutinizing test for typhoid fever and 

 Wasserman's fixation-of-the-complement test for the diagnosis of 

 syphilis. The conception that the toxic molecule has a "hapto- 

 phore" group and a "toxophore" group and that the cell has 

 receptors of a typical mechanical structure on which the hapto- 

 phores adjust themselves is so tangible that it makes immediate 

 and strange appeal to the imagination, or, better stated, it makes 

 it unnecessary to call the imagination into play at all, the dia- 

 grams supplying its place. 



I chanced to be living in London in 1900, and I had the pleas- 

 ure of hearing Ehrlich deliver his Croonion Lecture before The 

 Royal Society, expositing his epoch-making theory. Subse- 

 quently I visited Ehrlich at the famous Institute at Frankfort, 

 and talked with him about newer aspects of the great problem 

 of immunization, with particular reference to the possibilities of 

 specific therapy, which were then holding his attention in con- 

 nection with the development of salversan and the attempted 

 selenium cancer specific. My own original investigations have 

 led to developments rather along the line of extension of an- 

 other field in which Ehrlich was a pioneer, namely the study of 

 the tangible activities of the corpuscles; but like all workers in 

 allied fields I have found aid and stimulation in the graphic de- 

 signs with which Ehrlich attempted to make his conceptions 

 intelligible. 



Unquestionably these diagrams have proved very useful, and 

 the entire mechanical conception has done much to promul- 

 gate widely a more or less comprehensible conception of the 

 mechanism of immunity. But it is at least an open question as 

 to whether these diagrams have not now served their purpose, 

 and whether it may not be well to revert to a somewhat differ- 

 ent point of view, and, ultimately, to adopt a terminology more 

 in keeping with the expression of chemical ideas in general. For 

 of course it would be absurd to imagine that the mechanical dia- 



