10 INTRODUCTION. 
may be well to subjoin a few additional facts, derived fror 
the cholera-experience of 1848-9, which, from its genera 
diffusion, tested, in a very remarkable degree, the relativ 
healthfulness of different provincial towns, and of differen 
metropolitan districts. Thus, among the whole population o 
the ten towns of Exeter, Derby, Cheltenham, Leiceste: 
Nottingham, Rochdale, Norwich, Preston, Halifax, and Bir 
mingham, amounting to 657,000, there were no more thai 
238 deaths from cholera; whilst, in an equal population 
inhabiting the towns of Newcastle-under-Lyne, Plymouth 
Brighton, Merthyr Tydvil, Portsea, Tynemouth, Wigan, Hull 
Wolverhampton, and Leeds, the number of deaths was n 
fewer than 10,415, or forty-three times as great. So again, it 
twenty-five Metropolitan districts, chiefly on the north side o 
the Thames, having a total population of about 310,000, th 
number of deaths from cholera was only 389; whilst in 
twenty-two districts, almost entirely on the south side of th 
river, the number of deaths, out of a population of almos 
exactly the same amount, was 5,932, or more than ¢welv 
times as great. In no instance is there the least difficulty in 
accounting for these contrasts. They all point to the sam 
general conclusion ; that,. namely, of the immense influenc 
which is exercised over human health by the purity of the ait 
that is breathed, and of the water that is drunk; and it i 
because these two conditions are in a great degree capable o 
public regulation, that legislative interference has so much it 
its power, and is sd imperatively called for by the interests o 
humanity, which speak solemnly and distinctly to all whe 
claim the rights of property in the foul “ plague-spots” which 
deface our country, of their bounden duty to render them not 
unfit for human occupation. 
But although the magnitude of the evils resulting from the 
neglect of the conditions of Public Health, gives to this sub- 
ject the first claim on our consideration, yet it is not the les: 
important that every individual should acquire as much 
knowledge of the constitution of his body, and of the right 
means of keeping it in working order, as will save him from 
seriously damaging either himself or other people by hik 
ignorance of such matters. It is less than ten years since a 
fearful sacrifice of life occurred among the deck-passengers on 
board the Irish steamer “ Londonderry,” who were ordered 
