vni CONQUEST OF DISEASE 209 



mankind of the dragon of smallpox that had demanded 

 tens of thousands of victims annually. With the 

 Emperor Napoleon, Jenner was a great favourite. On 

 one occasion Napoleon was about to refuse a petition 

 from Jenner to allow two friends to return to England, 

 when Josephine reminded him that the petition was from 

 the discoverer of vaccination. " Ah," said the Emperor, 

 " Jenner, we can refuse nothing to that man." 



In recognition of the national value of vaccination, 

 the House of Commons voted Jenner a grant of 10,000 

 in 1802, and five years later a further grant of 20,000 

 was made to him, the intervening time having strength- 

 ened the general opinion as to the efficacy of vaccina- 

 tion and as to its great benefit to the nation at large. 

 Competent authorities would not now claim that a 

 single inoculation with vaccine lymph is a perfect 

 antidote against smallpox throughout life, but only 

 that it confers a high degree of protection against the 

 disease. Absolute immunity cannot be ensured in all 

 cases because of individual differences of the blood and 

 tissues of the human body ; yet with this reservation 

 the practice of vaccination has been completely justified. 

 We owe our deliverance from the fear of smallpox not 

 so much to improved sanitation, or to a natural decline 

 of the disease or acquired immunity from it, as to the 

 protective principle introduced by Jenner. The pro- 

 gress of preventive medicine depends largely upon the 

 application of this principle, which has proved to be of 

 even greater biological value than was anticipated by 

 Jenner or the physicians of his day. 



Many diseases of animals, as well as those of man, are 

 now controlled or conquered by the application of 

 scientific principles. Before science showed the nature 

 of anthrax, and provided the remedy, many thousands 



G.D. O 



