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 intro- 

 duced by Jenner. Though there is little doubt that a 

 contagium vivum is concerned in its occurrence, the etio- 

 logical relationship of any particular organism to smallpox 

 has still to be proved, and with regard to Jennerian vaccina- 

 tion, 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 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 in- 

 oculation (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 



