CHAP, xviii. VACCINATION A DELUSION. 235 



In the elaborate paper by Sir John Simon, on the 

 History and Practice of Vaccination, presented to Par- 

 liament in 1857 and reprinted in the First Report of the 

 Royal Commission, he tells us that the earlier evidence 

 of the value of vaccination was founded on individual 

 cases, but that now " from individual cases the appeal is 

 to masses of national experience." And the marginal 

 reference is, " Evidence on the protectiveness of vaccina- 

 tion must now be statistical." If this was true in 1857, 

 how much more must it be so now, when we have forty- 

 years more of " national experience " to go upon. Dr. 

 Guy, M. D., F. R. S., enforces this view in his paper 

 published by the Royal Statistical Society in 1882. He 

 says: " Is vaccination a preventive of small-pox? To 

 this question there is, there can be, no answer except 

 such as is couched in the language of figures." But the 

 language of figures, otherwise the science of statistics, is 

 not one which he who runs may read. It is full of pit- 

 falls for the unwary, and requires either special apti- 

 tude or special training to avoid these pitfalls and 

 deduce from the mass of figures at our command what 

 they really teach. 



A commission or committee of enquiry into this mo- 

 mentous question should have consisted wholly, or 

 almost wholly, of statisticians, who would hear medical 

 as well as official and independent evidence, would have 

 all existing official statistics at their command, and would 

 be able to tell us, with some show of authority, exactly 

 what the figures proved, and what they only rendered 

 probable on one side and on the other. But instead of 

 such a body of experts, the Royal Commission, which for 

 more than six years was occupied in hearing evidence 



