176 EDWARD JENNER 



economy, generated by it, is it not probable that different 

 parts of the human body may prepare or modify the virus 

 differently? Although the skin, for example, adipose mem- 

 brane, or mucous membranes are all capable of producing 

 the variolous virus by the stimulus given by the panicles 

 originally deposited upon them, yet I am induced to conceive 

 that each of these parts is capable of producing some vari- 

 ation in the qualities of the matter previous to its affecting 

 the constitution. What else can constitute the difference be- 

 tween the smallpox when communicated casually or in what 

 has been termed the natural way, or when brought on arti- 

 ficially through the medium of the skin? 



After all, are the variolous particles, possessing their true 

 specific and contagious principles, ever taken up and con- 

 veyed by the lymphatics unchanged into the blood vessels? I 

 imagine not. Were this the case, should we not find the blood 

 sufficiently loaded with them in some stages of the smallpox 

 to communicate the disease by inserting it under the cuticle, 

 or by spreading it on the surface of an ulcer? Yet experi- 

 ments have determined the impracticability of its being given 

 in this way; although it has been proved that variolous 

 matter, when much diluted with water and applied to the 

 skin in the usual manner, will produce the disease. But it 

 would be digressing beyond a proper boundary to go minutely 

 into this subject here. 



At what period the cow-pox was first noticed here is not 

 upon record. Our oldest farmers were not unacquainted with 

 it in their earliest days, when it appeared among their farms 

 without any deviation from the phenomena which it now ex- 

 hibits. Its connection with the smallpox seems to have been 

 unknown to them. Probably the general introduction of 

 inoculation first occasioned the discovery. 



Its rise in this country may not have been of very remote 

 date, as the practice of milking cows might formerly have 

 been in the hands of women only ; which I believe is the case 

 now in some other dairy countries, and, consequently, that 

 the cows might not in former times have been exposed to the 

 contagious matter brought by the men servants from the 

 heels of horses. 1 ' Indeed, a knowledge of the source of the 



18 1 have been informed from respectable authority that in Ireland, al- 





