Experiments refpenhig th» Vacdne B'feafe. 317 



ner very ufefuUy to human fociety, and very honourably lo 

 himfelf/firft publi(l>ed fome pacts, which I thought it my 

 duty, in common with other members of the profelhon to , 

 iaveftic^ate, and have laid before the public. Among thefc 

 Jaas the 4th and 5th were afferted by me in thefe terms: 

 IV A perfon hwAng been afc^ed nvUh the fpeafc J.jer 

 and local d^eafe produced hy the eO'W^pox poijon, u hahle t. 

 he again offered, as before, by the fame poijon; andyetjucb 

 perfon is not fufceptible of thefmall-pox. 



V. A perfon is ffceptible of the cow-pox ivho has oniece^ 

 dcntlj been affe^ed ivith thefmall-pox. 



Neither of thefe faas being fupported by any analog)-, a 

 . treat part of the public feemed inclined to difbelievc them ; 

 and not only inclined to difbelleve thefe fac^s, but the credit 

 of the others was for obvious reafons thereby weakened. 

 It may be feen in my In^idry, that I thought the affertione 

 flood in need of confirmation, which I was not only unable 

 to procure, but contravening evidence was obtamed. Some 

 of my correfpoudents not only afferted that men Were not 

 affected more than once, but that the fame cows had not 

 been known to be affeded more than once. It was aiia 

 pofitively afferted by fome, that - a perfon is not liable to 

 • the infedion of the cow-pox after going through the fmaU- 

 pox, (p. 49, I'^q^^U--) ^"d I faw perfons pitted with the 

 fmall-pox who had been much expofcd to the cow-po:< 

 without taking it, {Ibul. p. 50.) Notwithftanditig my con- 

 lldcnce in Dr. Jenner's evidence, I could not help pointing 

 out, in the following words, what I apprehended was a fource 

 of error in both cafes.—" The evidence for this fad (viz. 

 IV.), to my apprchcnfion, only proves falisfaa-rily that thfr 

 local affetlion of the cow-pox may occur in the fame perfon 

 n,ore than once ; but whether the peculiar fever alfo occurs 

 more than once in the fame perfon from the cow-pox poifoa 

 iloes not appear certain, and muft be du-tennincd by tiiiure 

 obfervalions nvadc with a particular view to this point." 

 karthcr: I was fo diffatisticd that I wrote to Dr. Jenner to 



aufwer 



