ON THE EXTERNAL 
CAUSES OF DISEASE. 
gravity of the atmospherical gases. But, leaving that out of 
the question, we are disposed to disagree with him upon more 
important grounds. When holes of the description which he 
has recommended are placed so immediately opposite the horse’s 
head, we are of opinion, whatever he may say to the contrary, 
that they are as likely to admit a current of cold air from without, 
as to assist in the withdrawing of the heated air from within; 
and we are well assured that a stream of cold air playing con¬ 
stantly on the head of a horse can be productive of no good. It was 
a generally received opinion at one time, that if a living body be 
suddenly exposed to cold when it is above the natural standard 
of heat, and especially if there be much perspiration, very great 
danger is to be apprehended. This is true only to a certain 
degree and in a particular manner: for instance, if the whole of 
the body be exposed at once, and completely, to an extraordinary 
degree of cold, no harm will happen; but if only a part of the 
body be thus exposed, we may expect a derangement of its 
functions in some shape or other. 
“ If the wind blows through a hole, 
Make your will, and take care of your 80111,” 
0 
says the Spanish proverb, and the saying is a very true one. 
Change from one extreme to the other ought always to be 
guarded against, and a uniform temperature should be preserved 
as much as possible in the stable. These are the Scylla and 
Charybdis, into which many persons have fallen; either keeping 
their horses in a constant chill by exposing them to currents of 
cold air; or, on the other hand, shutting out the least access to 
it, to prevent their “ catching cold,” as they commonly term it. 
It is needless, we presume, to observe that the terms made use 
of to express varieties of temperature are merely relative, the 
limits between heat and cold constantly varying with the parti¬ 
cular state of the body immediately previous to and at the time it 
is subjected to the impression. In general, however, below for¬ 
ty-five degrees is considered cold , above seventy hot, and the 
mean between the two, temperate . 
The operation of heat upon the living system is universally 
stimulant; the operation of cold (that is to sap, the absence of 
heat) is either tonic or sedative, according to the mode of its ap¬ 
plication; for the animal frame, like inanimate matter, is liable 
to have a portion of its heat abstracted from the external parts 
bv the application of a colder medium: but its inherent powers 
of regeneration, w r hen the impression of cold has been moderate 
and of short duration, quickly supply the portion withdraw n, and 
