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 concerned in its 

 occurrence, the etiological relationship of any particular organ- 

 ism to smallpox has still to be proved ; and with regard to 

 Jennerian vaccination, it is only the advance of bacteriological 

 knowledge which is now enabling us to understand the prin- 

 ciples which underlie the treatment, and which is furnishing 

 methods whereby the vexed questions concerned will probably 

 be satisfactorily settled. 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 

 inoculation method had long been practised in various parts of 

 the world, and had considerable popularity all over Europe 

 during the eighteenth century. Its disadvantage was that the 

 resulting disease, though mild, was still infectious, and thus 

 might be the starting-point of a virulent form among un- 

 protected 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 



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