INTRODUCTION. 
11 
below by the Captain on account of the stormy character of 
the weather, and on whom the hatches were closed down, 
although the cabin which was crowded by them had scarcely 
any other means of ventilation. Out of 150 of these unfor¬ 
tunates, no fewer than 70 died of suffocation before the 
morning,—a catastrophe only second to that which occurred 
in the “Black Hole of Calcutta,” in which 123 out of 146 
died during one night’s confinement in a room eighteen feet 
square, provided with only two small windows. Yet the 
Captain of the “ Londonderry ” was acquitted of all blame; 
since he had done what seemed to him best for the welfare of 
his passengers, the result being due simply to his astound¬ 
ing ignorance of the fact that men cannot live without having 
air to breathe. Hot a year passes without the occurrence of 
numerous deaths from the like cause; and yet these are 
really insignificant, when compared with the vast amount of 
disease which is constantly attributable to inattention, on the 
part of individuals, to those simple means of securing an 
adequate supply of air which are within the reach of every 
one. And when we bear in mind that the respiratory func¬ 
tion is only one of the processes whose due performance has 
to be provided for, and that the regulation of the food and 
drink, of the excretions, of clothing and temperature, of 
exercise (bodily and mental) and repose, and of the repro¬ 
ductive functions, all fall within rules which it is the pro¬ 
vince of Physiology to prescribe, we see how vain it is to 
expect that the body can be maintained in health, without 
some acquaintance with that science, or at least with the 
rules which it lays down. Por, although it is quite true that 
man has within himself certain instincts which afford him a 
considerable measure of guidance in all these particulars,— 
hunger and thirst, for example, leading him to take the 
sustenance which his body requires, weariness tempting him to 
needed repose, and so on,—yet it is no less certain that in a 
state of artificial civilisation these instincts are so often over¬ 
borne by acquired tastes, or by the pressure of other circum¬ 
stances, that they cannot alone be safely relied on. Hence it 
is all the more important that the rules for preserving health 
should be based on an intelligent knowledge of Physiological 
principles; otherwise, like the natural instincts, they are likely 
to be put aside as occasion prompts; whereas, in proportion as 
