THE METHOD OF EXPERIMENT 235 



is no possibility of ambiguity in the answer. This 

 is the method of experiment. It was the method 

 of Pasteur. 



Consider further for a moment the growth of 

 our knowledge concerning acute fevers during the 

 period which just preceded the work of Pasteur. 

 Jenner's observations, and the clear inductive 

 reasoning he based upon them, left the medical 

 world convinced that typhoid and typhus fevers 

 were distinct diseases. The bedside studies of 

 such men as Louis, Bartlett, Murchison, and many 

 others made for sound views and for a healthy 

 recognition of ignorance. Descriptions became 

 more accurate; the significance of this or that 

 symptom became better evaluated as the result 

 of statistical records, and a sharper classification 

 became possible. Nothing was added, however, 

 that appreciably widened the point of view; 

 nothing that could remove the utter vagueness 

 concerning the essential nature and cause of fevers, 

 or throw light on the mysteries of contagion. In 

 this respect the knowledge of the middle of the 

 nineteenth century scarcely differed from that of 

 the days of Sydenham. To a new era belonged 

 that moment when Pasteur, intruding into a vague 

 discussion concerning the 'cause' of puerperal 

 fever, rushed to the blackboard, made a rapid 

 sketch of a microbe and cried "Tenez, voici sa 

 figure ! " It is a great thing to see the face of 

 the enemy. 



