NEW CONCEPTIONS IN SCIENCE 



banish that disease from cleanly lands. But it was 

 merely a fluke, a ten-strike in the dark; to use a 

 large word, a purely empirical discovery. No one 

 had the slightest idea how the vaccine worked, for 

 no one, up to thirty or forty years ago, had so much 

 as a suspicion as to the nature or cause of any 

 disease. Jenner's discovery was not the fore- 

 runner of a host of others; it opened no new line 

 of inquiry. The physicians of his time and after 

 were far more interested in the fancies of Hahne- 

 mann than in a patient, scientific investigation of 

 these new and amazingly fertile results. 



Here, again, it fell to the chemist Pasteur to 

 take up this work half a century after Jenner was 

 dead. Knowing nothing of medicine or the stock- 

 in-trade absurdities taught in its name, and com- 

 ing fresh to the subject, he was able to reveal that 

 disease is essentially a fermentation, due, like the 

 fermenting of yeast, to the presence of a minute 

 fungus. Following the customary method of pre- 

 paring the small-pox vaccine, Pasteur and his aids 

 found that by deliberately cultivating his microbes 

 through a succession of young animals he was able 

 so to attenuate the poison they secrete as to make 

 the latter relatively harmless. Nevertheless, as in 

 the case of vaccination, the fungus thus modified 

 was able, by inducing a mild form of the disease, 

 to confer immunity against a more virulent attack. 



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