352 CREATA^ SCIENCE 



A parallel illustration from a very difiFerent context is reported by 

 Nicolle, who had been long tormented by his inability to solve this 

 mystery: typhus, violently contagious outside his hospital in Tunis, 

 was apparently noncommunicable within its walls. 



One day, just like any other, immersed no doubt in the puzzle of 

 the process of contagion in typhus, in any case not thinking of it 

 consciously (of this I am quite sure), I entered the doors of the 

 hospital, when a body at the bottom of the passage arrested my at- 

 tention. 



It was a customary spectacle to see poor natives, suffering from 

 typhus, delirious and febrile as they were, gain the landing and col- 

 lapse on the last steps. As always I strode over the prostrate body. It 

 was at this very moment that the light struck me. When, a moment 

 later, I entered the hospital, I had solved the problem. I knew beyond 

 all possible doubt that this was it. This prostrate body, and the door 

 in front of which he had fallen, had suddenly shown me the barrier 

 by which typhus had been arrested. For it to have been arrested, and, 

 contagious as it was in entire regions of the country and in Tunis, 

 for it to have remained harmless once the patient had passed the Re- 

 ception Office, the agent of infection must have been arrested at this 

 point. Now, what passed through this point? The patient had already 

 been stripped of his clothing and of his underwear; he had been 

 shaved and washed. It was therefore something outside himself, 

 something that he carried on himself, in his underwear, or on his 

 skin, which caused the infection. This could be nothing but a flea. 

 Indeed, it was a flea. The fact that I had ignored this point, that all 

 those who had been observing typhus from the beginnings of history 

 (for it belongs to the most ancient ages of humanity) had failed to 

 notice the incontrovertible and immediately fruitful solution of the 

 method of transmission, had suddenly been revealed to me. 



Such a report is the fruit of introspection, notorious for its un- 

 reliability. Yet these episodes are reported quite independently, and 

 from quite varied contexts, in strikingly similar terms. And, though 

 not numerous, such episodes are frequent enough to suggest some 

 degree of generality. In the modern era they are reported by mathe- 

 matical physicists like Newton (the apple), Gauss, Helmholtz, W. R. 

 Hamilton (who had inspiration while crossing, literally as well as 

 figuratixely, what thereafter he called Quaternion Bridge), and 

 Poincare; by the chemist Kekule ( two separate reveries or dreams ) ; 

 by the geologist Kropotkin; and by biological workers like Darwin 



