THE ART OF SCIENTIFIC INVESTIGATION 



of Others. This can be one of the most difficult hurdles of all 

 and it is here that the scientist occasionally has to fight and in the 

 past has sometimes even lost his life. The psychology of mental 

 resistance to new ideas, and actual opposition to discoveries are 

 discussed in a later chapter. 



Several of the points discussed in this and the preceding 

 section may be illustrated by narrowing the story of Jenner's 

 recognition of the potentialities of vaccination and his exploita- 

 tion of it. Artificial immunisation against smallpox by means 

 of inoculation with virulent smallpox material (variolation) had 

 long been practised in the Orient. Some say that looo years B.C. 

 it was the custom of China to insert material from smallpox 

 lesions into the noses of children, others that variolation was 

 introduced into China from India about a.d. iooo.^^' ^^' ^°* 

 Variolation was introduced from Constantinople into England 

 about the middle of the eighteenth century and became an 

 accepted though not very popular practice about the time that 

 Edward Jenner was bom. When Jenner was serving his appren- 

 ticeship between thirteen and eighteen years of age, his attention 

 was called to the local behef in Gloucestershire that people 

 who contracted cow-pox from cattle were subsequently immune 

 to smallpox. Jenner found that the local physicians were mostly 

 familiar with the traditional belief but did not take it seriously, 

 although they also were encountering instances of failure of 

 people to develop infection when given variolation after they 

 had had cow-pox. Jenner evidently kept the matter in mind 

 for years without doing anything about it. After returning to 

 country practice he confided in a friend that he intended trying 

 vaccination. He divulged his intentions under a bond of secrecy 

 because he feared ridicule if they should fail. Meanwhile he 

 was exercising his genius for taking pains and making accurate 

 observation by carrying out experiments in other directions. He 

 was making observations on the temperature and digestion of 

 hibernating animals for John Hunter, experimenting with agri- 

 cultural fertilisers for Joseph Banks and on his own behalf 

 carrying out studies on how the young cuckoo gets rid of its 

 fellow nestlings. He married at thirty-eight and when his wife 

 had a child he inoculated him with swine-pox and showed he 

 was subsequently immune to smallpox. Still none of his colleagues 



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