674 SUPPLEMENTARY APPENDIX. 



that, the prevalence of inoculation having greatly increased the amount 

 of small-pox, the diminution of small-pox in question was the result of 

 the decrease of inoculation. 



The question how far the behaviour of small-pox in the eighteenth 

 century and earlier was influenced by sanitary conditions, is one rendered 

 difficult by the lack of exact information. We may distinguish between 

 overcrowding as one insanitary condition and all other insanitary condi- 

 tions, such as lack of cleanliness and the like. A priori we should ex- 

 pect that a dense population, especially one of great internal movement, 

 and one in continual interchange with surrounding populations, by 

 offering greater facilities for the conveyance of contagion, would lead to 

 a greater amount of small-pox. London was a conspicuous instance of 

 the above, and the apparent greater prevalence of small-pox in London 

 than in the provinces may be attributed to these causes : but it would 

 appear that the increase was felt as indeed would, a priori, seem pro- 

 bable rather in the constant presence of small-pox to a considerable 

 amount at all times than in the mortality of the epidemics when these 

 occurred. And the same seems also to be shown to a less extent in other 

 large cities, such as Liverpool. But in this matter of dense and moving 

 populations the eighteenth century did not differ markedly from the 

 early part of the nineteenth. We might a priori expect the other 

 acknowledged imperfect sanitary conditions of the eighteenth century to 

 increase the fatality of, and so to a corresponding extent the mortality 

 from, small-pox ; but there is no exact evidence to confirm this supposi- 

 tion. If on the contrary we recognise that in the course of the eighteenth 

 century the general mortality, the relative number of deaths from all 

 causes, went on decreasing, and attribute, as has been done, this decrease 

 to improved sanitary conditions, no like decrease of small-pox took place. 

 Again, the places which were deemed the most salubrious appear to have 

 been visited by epidemics of small-pox as severe as those which fell on 

 unhealthy places. Thus the epidemic in Chester in 1774 was undoubtedly 

 a severe one, and yet Haygarth writes, " The healthiness of Chester," as 

 shown by statistics, " must appear so very extraordinary as to be almost 

 incredible." And in general both the incidence of, and mortality from, 

 small-pox seem to have been far less affected by sanitary conditions than 

 might a priori have been expected. 



It may be urged against the view that the decline of small-pox was 

 due to improved sanitary conditions, in the first place, that, admitting 

 the introduction of sanitary improvements, no evidence is forthcoming 

 to show that during the first quarter of the nineteenth century these 

 improvements differentiated that quarter from the last quarter, or half, 

 of the preceding century in any way at all comparable to the extent 

 of the differentiation in respect to small- pox. In the second place, 

 admitting a priori that crowded dwellings tend to increase the liability to 

 contagion, and so the prevalence of the disease, while other insanitary 

 conditions tend in addition to increase the fatality among those attacked, 

 that insanitary conditions as a whole must tend to increase the 

 mortality from small-pox, no evidence is forthcoming which distinctly 

 shows that the dependence of the prevalence of, or the mortality from, 



