SECTION. X. 

 INFECTIOUS DISEASES. 



COW-POX- VACCINIA. 



The name cow-pox, or vaccinia, is employed to describe a special 

 disease which in animals of the bovine species is characterised by 

 the development of pustules at points where the skin is fine, and 

 more particularly the mammary region. 



It can be conveyed both to man and the domestic animals. 



This disease has been known from time immemorial, and it would 

 appear that first of all in the East and later in England it was a 

 general belief that its attacks rendered human beings proof against 

 small-pox. Medical men, it must be admitted, long regarded this 

 belief as a popular delusion, as is proved by their continuing to 

 practise inoculation with true small-pox material. 



Jenner in 1770 was the first to declare the truth of this popular 

 opinion, and by his wise foresight to confer on humanity one of the 

 most beneficent discoveries ever made, although the weight of modern 

 opinion is in favour of the identity of cow-pox and human variola. 

 Having observed that milkmaids who happened to have small cuts 

 or sores about the hands sometimes contracted the disease in a mild 

 form, and that they did not afterwards suffer from small-pox, he was 

 struck with the advantages consequent on such a discovery, and having 

 proved the possibility of inoculating human beings artificially, he 

 immediately formulated the principles of vaccination. A child eight 

 years of age was vaccinated with cow-pox, and afterwards inoculated 

 with pus from a small-pox patient. It contracted vaccinia in con- 

 sequence of the first inoculation, but entirely resisted the attempt to 

 inoculate it with small-pox. Vaccination had been discovered. 



Jenner furthermore proved that cow-pox was transmissible from 

 cow to cow and from man to man, but it seemed to him that the 

 original disease was to be sought elsewhere, and that the pustular 

 affection originated primarily with the horse. The horse is some- 

 times the subject of a pustular disease called horse-pox; this disease 

 when inoculated in man confers immunity against small-pox, just as 

 does cow-pox, and Jenner believed that the disease did not attack 



