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 organism 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 principles which underlie the 

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

 future, the vexed questions concerned will probably be satis- 

 factorily 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 unprotected persons. 

 Jenner's discovery was published w r hen inoculation was still 

 considerably practised. It was founded on the popular belief 

 that those who had contracted cowpox from an affected animal 



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