4 THE BIRTH AND GROWTH OF SCIENCE IN MEDICINE. 



observation, with patient accumulation of the facts which 

 form the building-stones of science. The third, widely 

 different from the preceding, is the gift of imagination 

 which can frame a tentative explanation of the observed 

 facts — a rarer faculty in the chastened form demanded 

 by science, and perhaps a more dangerous one. The two 

 conditions last named are seen united only in exceptional 

 men : they were so in Harvey, who has left a clear record 

 of the mental processes which led him to the truth. In 

 the fourth place comes the verification of hypothesis by 

 experiment in which the conditions are so controlled as 

 to allow of more convincing conclusions than chance 

 observations permit. And governing the whole chain of 

 thought from its first inception there must be present 

 that capacity for severely correct thinking, the rules for 

 which are embodied in logic. Let us now see how the 

 history of medical science sheds light on the development 

 of these fundamental conditions. 



History has been said to be the story of the influence 

 of great men. It is true that we can associate the more 

 striking advances in medical science with the names of 

 individual men who stand out as landmarks in its develop- 

 ment, but the course of history is surely swayed by 

 influences deeper than this. A great man is the product 

 of his times. Harvey would not have discovered the 

 circulation had it not been for the labours of his pre- 

 decessors and the intellectual atmosphere in which he 

 lived. The great man is he who has the vision to combine 

 the scattered facts into a harmonious whole, and who 

 can carry conviction to others by the force of his reasoning. 

 I shall have to commemorate such great names standing 

 along the history of medical science, but I shall also be 

 obliged to consider the conditions which produced them. 



In his suggestive little book, entitled ' The Revolutions 

 of Civilisation,' Prof. Flinders Petrie has pointed out that 

 culture is an intermittent phenomenon. No civilisation 

 in the past has proved permanent, and he estimates the 

 average duration of any given period of culture at about 



