IMMUNITY. 297 



material from small-pox pustules was resorted 

 to for the purpose of obtaining protective in- 

 oculation, and, later, in the Orient, the method 

 of inoculating pustule scabs beneath the skin 

 came into vogue. This latter method, the so- 

 called practice of variolation was introduced 

 from Constantinople into Western Europe by 

 Lady Mary Wortley Montague between 1717 

 and 1721. European physicians learned the 

 art so well that only an inconsiderable propor- 

 tion of those treated died of the artificial small- 

 pox inoculation while an enormous number of 

 men ordinarily perished with natural small- 

 pox. Those individuals who passed through 

 the artificially induced small-pox were almost 

 as well protected against the disease as those 

 who had at much greater peril overcome the 

 natural contagion. 



It was observed at a later date by herdsmen 

 and milk-maids in both England and Schles- 

 wig-Holstein that cows occasionally developed 

 on the udder an eruption resembling small- 

 pox, and that this was communicated to the 

 persons engaged in milking. Those who had 

 been thus infected with " original " cow-pox, 

 which at first was regarded as a peculiar dis- 

 ease, were often protected just as well during 

 epidemics of true small-pox as those who had 

 had the small-pox. These observations were 



