16 
FRED. TORRANCE. 
4 * small-pox that I think it highly probable that it may be the 
“ source of that disease.” 
These last words point to the horse-pox as the probable origin 
of human variola, but if Jenner thought it the cause of what he 
calls the u severest scourge of the human race,” he also ascribes 
to it the origin of vaccination ; for in the next paragraph lie con¬ 
tinues : u In this dairy country a great number of cows are kept, 
“ and the office of milking is performed indiscriminately by men 
li and maid servants. One of the former having been appointed 
“ to apply dressings to the heels of a horse affected with the mal- 
“ ady I have mentioned, and not paying due attention to clean- 
u liness, incautiously bears his part in milking the cows, with 
“ some particles of the infectious matter adhering to his fingers. 
“ When this is the case it frequently happens that a disease is 
“ communicated to the cows, and from the cows to the dairy- 
“ maids, which spreads through the farm until most of the cattle 
<£ and domestics feel its unpleasant consequences. This disease 
“ has obtained the name of the cow-pox.” 
These extracts are interesting as showing the views held by 
Jenner, of the relation of horse-pox and cow-pox to small-pox, 
views which have been considerably modified by the more search¬ 
ing investigations of recent years. 
That cow-pox can originate from the inoculation of variolous 
matter from the horse is well known, but that it is always caused 
in this way is extremely doubtful, and it is more probable that 
this is an irregular mode of origin. The question of the origin 
of cow-pox, however, is not of as much practical importance as 
the relation of both horse-pox and cow-pox to small-pox, from its 
connection with vaccination. The deterioration of lymph stocks, 
and the difficulty of finding cases of genuine cow-pox from which 
to renew them, have led to the inoculation of cows with small¬ 
pox virus in the hope of obtaining from them fresh supplies of 
vaccine lymph. Success has been attained in many instances, 
particularly Ceely and Babcock in England, and Drs. Gassner 
and Thiele on the Continent; but other experimenters, after many 
attempts, have failed completely. Even those who have been 
successful speak of the difficulty of producing the disease in the 
