CHANCE 



tion with the virus of mumps and later of mouse pneumonia 

 was discovered. 



Rickettsiae (microbes closely related to viruses) cause typhus 

 and several other important diseases and are difficult to cultivate. 

 Dr. Herald Cox spent much time and effort trying to improve on 

 methods of growing them in tissue culture and had tried adding 

 all sorts of extracts, vitamins and hormones without achieving 

 anything. One day while setting up his tests he ran short of chick 

 embryo tissue for tissue culture, so to make up the balance he 

 used yolk sac which previously he, like everyone else, had 

 discarded. When he later examined these cultures, to his "amaze- 

 ment and surprise", he found terrific numbers of the organisms 

 in those tubes where he had happened to put yolk sac. A few 

 nights later while in bed the idea occurred to him of inoculating 

 the rickettsiae directly into the yolk sac of embryonated eggs. 

 Getting out of bed at 4 a.m. he went to the laboratory and made 

 the first inoculation of rickettsiae into the yolk sac. Thus was 

 discovered an easy way of growing masses of rickettsiae, which 

 has revolutionised the study of the many diseases they cause and 

 made possible the production of effective vaccines against them. 

 [Personal communication.] 



Role of chance in discovery 



These ten examples, together with nineteen others given in the 

 Appendix and some of those in Chapters Four and Eight provide 

 striking illustration of the important part that chance plays in 

 discovery. They are the more remarkable when one thinks of the 

 failures and frustrations usually met in research. Probably the 

 majority of discoveries in biology and medicine have been come 

 upon unexpectedly, or at least had an element of chance in them, 

 especially the most important and revolutionary ones. It is scarcely 

 possible to foresee a discovery that breaks really new ground, 

 because it is often not in accord with current beliefs. Frequently 

 I have heard a colleague, relating some new finding, say almost 

 apologetically, " I came across it by accident." Although it is 

 common knowledge that sometimes chance is a factor in the 

 making of a discovery, the magnitude of its importance is seldom 

 realised and the significance of its role does not seem to have 

 been fully appreciated or understood. Books have been written on 



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