6 
INTRODUCTION. 
proportion to the improvement of the places it previously 
infested, in respect to ventilation and cleanliness. Thus, it is 
so rare for a case of it now to occur in London, that many 
practitioners of large experience have never seen the disease. 
In the Dublin Lying-in Hospital, the number of deaths from 
it has been reduced to three or four yearly. And there can¬ 
not be a reasonable* doubt, that, by due attention to the same 
conditions, it might be exterminated from Iceland and from 
St. Hilda. There is scarcely, in fact, a disease incident to 
humanity, which is more completely preventable than this; 
and yet the annual sacrifice of life which it formerly caused 
in our own country alone, might have been reckoned by tens 
of thousands. 
Although the peculiar susceptibiltty of the constitution of 
children, gives to foul air and other causes of disease a much 
more destructive influence over them, than the. like causes 
have over persons more advanced in life, yet it is now well 
ascertained that the rate of mortality among different classes 
of the community varies in a degree which bears a very close 
relation to the nature of the conditions under which they live. 
Thus, whilst the annual average number of deaths in the whole 
of England and Wales is about. 22 out of every thousand 
persons living, there are localities in which the annual 
average exceeds 50 in a thousand, and others in which it falls 
as low as 11 in a thousand. And it is not a little remarkable, 
that the difference is almost entirely referable to the mortality 
produced by Fevers and allied diseases, which, as experience 
has now fully demonstrated, are absolutely preventible by due 
attention to the ordinary conditions of health. 
As the population of England and Wales may at present be 
estimated at about twenty millions, and its actual mortality at 
about 440,000, what maybe termed its inevitable mortality— 
arising from diseases that would not be directly affected by 
sanitary improvements—would be only one half, or 220,000 ; 
so that the same number of lives may be considered to be 
annually sacrificed by the public neglect of the means of pre¬ 
serving them,“—the deaths from typhus alone being no fewer 
than 50,000. But as it is scarcely to be supposed that every 
part of our population could be placed in conditions as favour¬ 
able as those which prevail where the rate of mortality is 
the lowest, we may take 13 per thousand as the average to 
