246 
THE EAT. 
In the first place, perspiration is that compound fluid 
which passes out through the pores of our skins, commonly 
known as sweat, and which sweat is composed of carbonic 
acid gas, human fat, water, &c., and is not only most 
offensive in its odour, but to a certain extent poisonous. 
In the next place, perspiration is divided, as it were, into 
two sorts, namely, the sensible and the insensible perspira- 
tion. The sensible perspiration is that moist state of the 
skin occasioned by heat or exertion, and which we can both 
see and feel, and wipe off if necessary ; but if viewed 
through a very powerful magnifying glass, it will be found 
spurting a foot or two from every part of the body, like so 
many little water-spouts, and in such numbers, that the 
body on every side seems enveloped in steam. 
The insensible perspiration is that gentle discharge from 
the pores, which is ever going on, and renders the skin soft, 
but not wet, and spurts only a few inches from the body ; 
but at all times it is regulated by temperature, action, or 
excitement. 
Now we can understand what we call a cold. If we get 
chilled in any way it stops up the pores ; consequently, the 
carbonic acid gas and humours of the body are kept in, and 
then we feel feverish and unwell, and begin to cough. 
What is more, we shall not be better till exercise, or physic, 
or some other agency, has opened these valves, and let out the 
noxious gas, &c. Everything we wear, even to the very 
soles of our boots, is, I may say, saturated with perspira- 
tion. This not only shows us the necessity for clean linen, 
(fee, but the great mischief also attending the ordinary use 
of water-proof clothing ; for that solution of India-rubber, 
which so effectually keeps out the wet, does as effectually 
keep in the perspiration. At the same time we can per- 
fectly understand how it is that different kinds of animals 
can track us out by scent. 
The most striking instance of this kind I ever met witli 
was reported in the papers about thirty years since. Some 
gamekeepers came to the spot where a deer had been killed 
in the night time. In order to discover the poacher, they 
put an old bloodhound on his trail. The dog tracked him 
to the neighbouring town, and though it was market-day, 
and all the people busy buying and selliug, he scented him 
