40 



HUMAN BIOLOGY 



37. Smallpox and vaccination. Smallpox was once so common 

 that scarcely one person in a hundred escaped it. It was intro- 

 duced into America by the Spaniards, it destroyed 3,500,000 people 

 in Mexico, and spread with frightful rapidity throughout the New 



World, until in 

 1733 it nearly de- 

 populated Green- 

 land. Mankind is 

 indebted to Dr. 

 Edward Jenner 

 (Fig. 17), an Eng- 

 lish physician, who 

 in 1796 proved 

 that vaccination is 

 a sure method of 

 preventing the dis- 

 ease. In vaccina- 

 tion our bodies re- 

 ceive germs that 

 originally came 

 from smallpox, but 

 which have been 

 so modified that 

 they cause a mild 

 form of disease 

 very different from 

 smallpox itself. 

 The cells produce 



(From International Enclyclopedia. Courtesy of Dodd, some form of anti- 

 Mead & Co.). 



toxin which is ef- 

 fective protection when we are exposed to the disease. This kind 

 of protection does not last indefinitely, however, and every person 

 should make sure that successful vaccination is performed at least 

 once in ten years, and oftener than that if cases of smallpox develop 

 in the community in which he is living. If a person has been act- 

 ually exposed to the disease, he should be vaccinated immediately. 



FIG. 17. Dr. Edward Jenner, English physician. 

 Born 1749. Died 1823. 



