APPENDIX A. 



SMALLPOX AND VACCINATION. 



SMALLPOX is a disease to which much study has been devoted, owing, 

 on the one hand, to the havoc which it formerly wrought among the 

 nations of Europe a havoc which at the present day it is difficult to 

 realise, and on the other hand, to the controversies which have arisen 

 in connection with the active immunisation against it introduced by 

 Jenner. Though there is little doubt that a contagium vivum is con- 

 cerned in its occurrence, the etiological relationship of any particular 

 organism to smallpox has still to be proved ; and with regard to Jen- 

 nerian vaccination, it is only the advance of bacteriological knowledge 

 which is now enabling us to understand the principles which underlie 

 the treatment, and which is furnishing methods whereby, in the near 

 future, the vexed questions concerned will probably be satisfactorily set- 

 tled. We cannot here do more than touch on some of the results of 

 investigation with regard to the disease. 



Jennerian Vaccination. Up to Jenner's time the only means adopted 

 to mitigate the disease had been by inoculation (by scarification) of 

 virus taken from a smallpox pustule, especially from a mild case. By 

 this means it was shown that in the great majority of cases a mild form 

 of the disease was originated. It had previously been known that one 

 attack of the disease protected against future infection, and that the 

 mild attack produced by inoculation also had this effect. This inocula- 

 tion method had long been practised in various parts of the world, and 

 had considerable popularity all over Europe during the eighteenth cen- 

 tury. Its disadvantage was that the resulting disease, though mild, was 

 still infectious, and thus might be the starting-point of a virulent form 

 among unprotected persons. Jenner's discovery was published when 

 inoculation was still considerably practised. It was founded on the 

 popular belief that those who had contracted cowpox from an affected 

 animal were insusceptible to subsequent infection from smallpox. In 

 the horse there occurs a disease known as horsepox, especially tending 

 to arise in wet cold springs, which consists in an inflammatory condition 

 about the hocks, giving rise to ulceration. Jenner believed that the 

 matter from these ulcers, when transferred by the hands of men who 



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