MIRACLES' OF SCIENCE 



The graphic diagrams with which Ehrlich illus- 

 trates his theory are of course purely imaginary, 

 inasmuch as toxins and antitoxins alike lie far be- 

 yond the range of the microscope. But it is always 

 helpful to the investigator of abstruse topics to be 

 able to visualize his work. As I said before, the 

 side-chain theory holds a unique place in this regard. 

 It is applicable all along the line in the studies of 

 immunization, and it has been pretty generally ac 

 cepted as a working hypothesis. The specific bloou 

 tests of Widal for typhoid fever and of Von Wasser- 

 mann for syphilis have been developed and explained 

 in the light of the side-chain theory; and the new 

 vaccine therapy, which stimulates the cells to act by 

 introducing dead toxic germs, falls equally within 

 its scope. The theory may also be used to explain 

 the very puzzling phenomena of excessive suscepti- 

 bility to certain protein substances blood-serum, 

 white of egg, and vegetable albumens, as well as 

 bacterial proteins to which the term anaphylaxis is 

 applied. But perhaps the most important benefits 

 derived from the theory, have grown out of the work 

 of Ehrlich himself, and his immediate associates, in 

 the development of the new chemo-therapy. 



THE SEARCH FOR SPECIFICS 



The very essence of the side-chain theory, it will 

 be observed, is the assumption that each specific 

 toxin has unit particles of a definite shape and can 

 be combatted only by particles of complementary 

 shape, just as a given key fits only its companion 

 lock. A vast body of observations in varied fields 

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