THE PRESIDENT'S ADDRESS. 185 



or at least to be made probable, which were previously considered 

 mere curiosities, as it were. I allude to those very curious bastard 

 forms of disease which are observable from time to time, the forms 

 connecting different diseases with each other — diphtheria and scar- 

 latina for instance, or scarlatina and measles. The manifestation 

 of particular disease germs may be extraordinarily affected by the 

 condition of the body in which they fructify. The small-pox 

 of 200 years ago was a very different disease from the miti- 

 gated small-pox propagated by inoculation, before vaccination 

 came into use — the old malignant type of small-pox, in which 

 patients died within a few clays after taking the disease, frequently 

 before any eruption appeared at all, but with large patches of 

 sub-cutaneous effusion — purpuric effusion — under the skin, that 

 was known as the black-pox, which was described 250 years ago 

 as having ravaged continental Europe with a severity even greater 

 than the plague. That black-pox was prevalent in this country, 

 as we learn from medical writings, and not only medical but 

 historical, or the writings of the ordinary chroniclers of the times — 

 that black-pox was prevalent, carrying off whole families some- 

 times, and the accounts given show that it was one of the most 

 horribly loathsome of all diseases. Now, in the treatises on small- 

 pox written by the best observers during the present century, 

 that malignant small-pox is mentioned merely as a form which may 

 show itself once now and then, but of which nobody has ever seen 

 an epidemic in this present century, and my belief is that the effect 

 of inoculation with small-pox was to eliminate this, because inocu- 

 lation was only practised when a favourable epidemic of small- 

 pox — that is an epidemic in which these malignant cases did not 

 occur — was prevalent, and the cases selected for taking the virus 

 from were mild cases, and that in that way everybody being 

 inoculated with the small-pox, except in out-of-the-way country 

 places, the malignant form, as it were, died out. It was, in fact, as 

 in a somewhat similar way, getting rid of that malignant form, as 

 Pasteur's inoculation of sheep gets rid of the malignant chabon. 

 It is on record that the mortality of small-pox towards the end of 

 the last century, when protected by inoculation, was often not more 

 than one in 100. I have lately seen a paper, which was com- 

 municated to the Society of Arts a few weeks ago, on inoculation 

 as practised among some of the hill-tribes of India not more than 

 20 years ago, and there the result seems to have been the same. 



