Original Vaccine Pock In it it niton. 673 



infection at all, if it has been rendered incapable of under- 

 going the small -pox a second time, by having already gone 

 through this disease. Hence the truly important practical 

 conclusion,— That inoculation with vaccine, matter affords an 

 equally just criterion of the state of unsusceptibilily of 

 either small -pox or the cow-pock, subsequent to either of 

 these affections. 



" On the grounds of fhe above different sources of evidence) 

 the opinion of the medical establishment in general seemed to 

 incline to that of the asserted failures after vaccination being 

 either imputable to certain chcumstances not. being attended 

 to, which might have shown that the patients were not dulv 

 vaccinated ; or else that the subsequent disorder was not 

 substantiated to be really the small-pox. But the occurrence 

 in May last, of two failures in the practice at this institu- 

 tion, compelled us to own that persons who have gone 

 through the cow-pock with all the appearances, and in the 

 course deemed, as we apprehend, by competent judges, to 

 be those of the cow-pock, and which are alleged by them 

 to give security — I say, that after such an affection the small- 

 pox may take place in a small proportion of the. number vac- 

 cinated. These two adverse occurrences unfortunately ren- 

 dered our opinion of a former case of small-pox after cow- 

 pock no longer tenable ; namely, that an error .had probably 

 crept into our register of the case of M'Pherson. As it 

 does not appear that the three above failures were owing to 

 any known measures or circumstances, and as the inocula- 

 tions were in circumstances supposed adequate for obtaining 

 security, we must conclude, that according to our expe- 

 rience, vaccine inoculation does not in all cases produce the 

 unsusceptibility desired. It is, however, abundantly proved 

 by the preceding evidence, that the proportion of insecure 

 cases is very small. Every estimate must be on grounds 

 merely conjectural ; but on such grounds it may be stated 

 to be one out of a thousand. However, it ought to be also 

 Slated, that this proportion is on the supposition that all 

 persons left susceptible of the small-pox after cow-pock 

 have taken the former disease, which is obviously hitherto 

 undecided. These being truths, false conclusions, a* it 

 ROW appears, have been drawn, viz. 1. That the inocula- 



V\»U 35. >io. 09. Aug. isuG. S tion 



