170 EDWARD JENNER 



I shall now conclude this inquiry with some general 

 observations on the subject, and on some others which are 

 interwoven with it. 



Although I presume it may be unnecessary to produce fur- 

 ther testimony in support of my assertion "that the cow-pox 

 protects the human constitution from the infection of the 

 smallpox/' yet it affords me considerable satisfaction to say 

 that Lord Somerville, the President of the Board of Agricul- 

 ture, to whom this paper was shewn by Sir Joseph Banks, 

 has found upon inquiry that the statements were confirmed 

 by the concurring testimony of Mr. Dolland, a surgeon, who 

 resides in a dairy country remote from this, in which these 

 observations were made. With respect to the opinion ad- 

 duced " that the source of the infection is a peculiar morbid 

 matter arising in the horse," although I have not been able 

 to prove it from actual experiments conducted immediately 

 under my own eye, yet the evidence I have adduced appears 

 sufficient to establish it. 



They who are not in the habit of conducting experiments 

 may not be aware of the coincidence of circumstances neces- 

 sary for their being managed so as to prove perfectly deci- 

 sive; nor how often men engaged in professional pursuits are 

 liable to interruptions which disappoint them almost at the 

 instant of their being accomplished : however, I feel no room 

 for hesitation respecting the common origin of the disease, 

 being well convinced that it never appears among the cows 

 (except it can be traced to a cow introduced among the 

 general herd which has been previously infected, or to an 

 infected servant) unless they have been milked by some one 

 who, at the same time, has the care of a horse affected with 

 diseased heels. 



The spring of the year 1797, which I intended particularly 

 to have devoted to the completion of this investigation, 

 proved, from its dryness, remarkably adverse to my wishes; 

 for it frequently happens, while the farmers' horses are ex- 

 posed to the cold rains which fall at that season, that their 

 heels become diseased, and no cow-pox then appeared in the 

 neighbourhood. 



The active quality of the virus from the horses' heels is 

 greatly increased after it has acted on the nipples of the 





me 



