CHAP. xvm. VACCINATION A DELUSION. 215 



from the East in the early part of the eighteenth cen- 

 tury, it was quickly welcomed, because a mild form of 

 the disease was produced which rarely caused death or 

 disfigurement, though it was believed to be an effectual 

 protection against taking the disease by ordinary infec- 

 tion. It was, however, soon found that the mild small- 

 pox usually produced by inoculation was quite as infec- 

 tious as the natural disease, and became quite as fatal 

 to persons who caught it. Toward the end of the last 

 century many medical men became so impressed with its 

 danger that they advocated more attention to sanitation 

 and the isolation of patients, because inoculation, though 

 it may have saved individuals, really increased the total 

 deaths from small-pox. 



Under these circumstances we can well understand 

 the favorable reception given to an operation which 

 produced a slight, non-infectious disease, which yet was 

 alleged to protect against small-pox as completely as did 

 the inoculated disease itself. This was Vaccination, 

 which arose from the belief of farmers in Gloucester- 

 shire and elsewhere that those who had caught cow-pox 

 from cows were free from small-pox for the rest of their 

 lives. Jenner, in 1798, published his " Inquiry," giving 

 an account of the facts which, in his opinion, proved 

 this to be the case. But in the light of our present 

 knowledge we see that they are wholly inconclusive. 

 Six of his patients had had cow-pox when young, and 

 were inoculated with small-pox in the usual way from 

 twenty-one to fifty-three years afterward, and because 

 they did not take the disease, he concluded that the cow- 

 pox had preserved them. But we know that a consid- 

 erable proportion of persons in middle age are insus- 



