© National Portrait Gallery 



EDWARD JENNER (1749-1823) 



Jenner had received irregular but good training in pharmacy and surgery, having 

 studied under the great John Hunter; but he preferred to practice medicine in his 

 small home town. Hearing of the common belief that those who had recovered from 

 the "cowpox" — a mild disease common among dairy workers — could not take small- 

 pox, he watched for a chance to test this experimentally. From his work the practice 

 of vaccination rid the world, in time, of smallpox, except in a few out-of-the-way 

 places 



called this mild disease Variola vaccinae (that is, cow-variola; vaccinae is 

 from the Latin vacca, "cow"). Today the term vaccination is used loosely 

 for any procedure that brings about immunity, whether or not the active 

 "germ" or virus is introduced. The general principle involved is that foreign 

 material stimulates the organism to produce something that counteracts //. 

 That is, as a result of the treatment, the body actively produces the anti- 

 bodies. This is in contrast to inducing passive immunity by adding antitoxin 

 to the blood, as in a case of diphtheria. 



In typhoid-fever "vaccination", cultures of the bacteria are killed and 

 then introduced under the skin. Active immunity against diphtheria is 

 brought about by means of a mixture of the toxin with some antitoxin. The 

 antitoxin protects the body against the poison, but the free toxin stimulates 



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