CHAP. xvm. VACCINATION A DELUSION. 217 



cause of uncertainty arises from the fact that this " vari- 

 olous test " consisted in inoculating with small-pox virus 

 obtained from the last of a series of successive patients 

 in whom the effect produced was a minimum, consisting 

 of very few pustules, sometimes only one, and a very 

 slight amount of fever. The results of this test, whether 

 on a person who had had cow-pox or who had not had it, 

 were usually so slight that it could easily be described by 

 a believer in the influence of the one disease on the other 

 as having " no effect " ; and Dr. Creighton declares, 

 after a study of the whole literature of the subject, that 

 the description of the results of the test is almost always 

 loose and general, and that in the few cases where more 

 detail is given the symptoms described are almost the 

 same in the vaccinated as in the unvaccinated. Again, 

 no careful tests were ever made by inoculating at the 

 same time, and in exactly the same way, two groups of 

 persons of similar age, constitution, and health, the one 

 group having been vaccinated, the other not, and none 

 of them having had small-pox, and then having the 

 resulting effects carefully described and compared by 

 independent experts. Such " control " experiments 

 would not be required in any case of such importance as 

 this; but it was never done in the early days of vaccina- 

 tion, and it appears never to have been done to this day. 

 The alleged " test " was, it is true, applied in a great 

 number of cases by the early observers, especially by 

 Dr. Woodville, physician to a small-pox hospital; but 

 Dr. Creighton shews reason for believing that the lymph 

 he used was contaminated with small-pox, and that the 

 supposed vaccinations were really inoculations. This 

 lymph was widely spread all over the country, and was 



