190 EDWARD JENNER 



have ascribed to it, namely, that of affecting the constitution 

 with a specific disease, is a truth that no subsequent occur- 

 rence has yet led me to doubt. But as I am now endeavour- 

 ing to guard the public as much as possible against erroneous 

 conclusions, I shall observe that when this pustule has de- 

 generated into an ulcer (to which state it is often disposed 

 to pass unless timely checked), I suspect that matter possess- 

 ing very different properties may sooner or later be pro- 

 duced; and although it may have passed that stage wherein 

 the specific properties of the matter secreted are no longer 

 present in it, yet when applied to a sore (as in the casual 

 way) it might dispose that sore to ulcerate, and from its 

 irritation the system would probably become affected; and 

 thus, by assuming some of its strongest characters, it 

 would imitate the genuine cow-pox. 



From the preceding observations on the matter of small- 

 pox when decomposed it must, I conceive, be admitted that 

 cow-pox matter in the state now described may produce 

 a disease, the effects of which may be felt both locally and 

 generally, yet that the disease thus induced may not be ef- 

 fectual in obviating the future effects of variolous con- 

 tagion. In the case of Mary Miller, related by Mr. Kite 

 in the volume above alluded to, it appears that the inflam- 

 mation and suppuration of the inoculated arm were more 

 than usually severe, although the system underwent no 

 specific change from the action of the virus; which ap- 

 pears from the patient's sickening seven weeks afterwards 

 with the natural smallpox, which went through its course. 

 Some of the cases communicated by Mr. Earle tend further 

 to confirm this fact, as the matter there manifestly pro- 

 duced ulceration on the inoculated part to a considerable 

 extent. 



Fourthly. Whether the cow-pox is a spontaneous disease 

 in the cow, or is to be attributed to matter conveyed to the 

 animal, as I have conceived, from the horse, is a question 

 which, though I shall not attempt now fully to discuss, yet 

 I shall digress so far as to adduce some further observa- 

 tions, and to give my reasons more at large for taking up 

 an opinion that to some had appeared fanciful. The ag- 

 gregate of these observations, though not amounting to 





