172 THE MAIN CURRENTS OF ZOOLOGY 



Jenner went to work on his own account to investi- 

 gate the basis of the belief of the dairy people of his 

 native county. 



After some experimentation he devised means of 

 vaccinating people with the relatively harmless virus 

 of cow-pox. In 1796, he made inoculations with 

 cow-pox material and after the recovery of his 

 patients from a mild sickness, in two months, he 

 inoculated the same individuals with small-pox 

 matter but they remained unaffected. This con- 

 vinced Jenner that this method was a protection 

 against the contagion of small-pox, and two years 

 after, in 1798, he announced his discovery to the 

 world. 



It was immediately put into use and Jenner was 

 heralded as a great benefactor. Even before Jenner 

 the voluntary inoculation with the virus of small-pox 

 had been advocated. The disease was so prevalent 

 and the chance to escape the contagion was so small 

 that some were willing to run the risk of a voluntary 

 inoculation, under the belief that these inoculations 

 resulted in mild cases, but these were sometimes 

 fatal. 



Jenner, however, investigated the matter with 

 scientific methods and devised a method of procuring 



