THE CONQUEST OF DISEASE 



as to furnish to all the world an example of 

 the preventive treatment of diseases. Small- 

 pox which was once a pestilence is now rare, 

 and could be stamped out absolutely if vacci- 

 nation and revaccination were universally prac- 

 tised. We can not say what role animal exper- 

 imentation played in the discovery of vaccina- 

 tion, for it is wrapped in the obscurity of 

 antiquity; but in the development of modern 

 vaccine, the cows which lend themselves to 

 experimental study are many. 



Vaccination for small-pox was popularized 

 in England by Jenner in 1798. It came into 

 general use in the early part of the following 

 century; provision for its gratuitous employ- 

 ment among the poor was made in 1840; and 

 laws for its systematic use were enforced in 

 1871. At the time of the introduction of vacci- 

 nation two-thirds of all the children born in 

 Europe were destined to have small-pox, and 

 one-twelfth of all born died of that disease. It 

 was as serious a scourge as tuberculosis now 

 is. In London from 1771 to 1780 there 

 was an average of 50,000 deaths from all causes 

 to every million of population. Five thousand 

 and twenty of these deaths were from small- 

 pox. That is, one death in every ten was from 



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