THE ART OF SCIENTIFIC INVESTIGATION 



practice. The fact that others who had the same opportunity 

 failed to discover vaccination and that it took Jenner thirty 

 years shows what a difficult discovery it was to make. Animals 

 were at that time regarded with repugnance by most people 

 so the idea of infecting a human being with a disease of animals 

 created utmost disgust. All sorts of dire results were prophesied, 

 including " cow-mania " and " ox-faced children " (one was 

 actually exhibited ! ) . Like many great discoveries it did not 

 require great erudition- and it mainly devolved on having bold- 

 ness and independence of mind to accept a revolutionary idea 

 and imagination to realise its potentialities. But Jenner also 

 had practical difficulties to overcome. He found that cows 

 were subject to various sores on the teats, some of which 

 also affected the milkers but did not give immunity to small- 

 pox. Even present day virus specialists have great difficulty 

 in distinguishing between the different types of sores that 

 occur on cows' teats; and the position is comphcated by 

 observations suggesting that an attack of cow-pox does not confer 

 immunity against a second attack of the same disease in the cow, 

 a point Jenner himself noted. 



Jenner's discovery has its element of irony which so often lends 

 additional interest to scientific anecdotes. Modem investigators 

 believe that the strains of vaccinia now used throughout 

 the world for many years are not cow-pox but have derived 

 from smallpox. Their origin is obscure but it seems that in the 

 early days cow-pox and smallpox got mixed up and an attenuated 

 strain of smallpox developed and was mistakenly used for 

 cow-pox. 



SUMMARY 



New knowledge very often has its origin in some quite un- 

 expected observation or chance occurrence arising during an 

 investigation. The importance of this factor in discovery should 

 be fully appreciated and research workers ought deliberately to 

 exploit it. Opportunities come more frequently to active bench 

 workers and people who dabble in novel procedures. Interpreting 

 the clue and realising its possible significance requires knowledge 

 without fixed ideas, imagination, scientific taste, and a habit of 

 contemplating all unexplained observations. 



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