Edward Jenner, who discovered that it is possible to vaccinate against Small Pox 
using material from Cow Pox, is rightly the man who started the science of 
immunology. However, over the passage of time many of the details surrounding 
his astounding discovery have been lost or forgotten. Also, the environment 
within which Jenner worked as a physician in the countryside, and the state of 
the art of medicine and society are difficult to appreciate today. It is 
important to recall that people were still being bled at the time, to relieve 
the presence of evil humors. Accordingly, this review details Jenner's discovery 
and attempts to place it in historical context. Also, the vaccine that Jenner 
used, which decreased the prevalence of Small Pox worldwide in his own time, and 
later was used to eradicate Small Pox altogether, is discussed in light of 
recent data.