COLD APPLICATIONS VS. COUNTER—IRRITATION. 
m 
—has been carefully blanketed when in the stable, and his over¬ 
coat, as it may be termed, is removed when he is taken out in 
the colder air ; or the patient may have been in some draught, 
etc. The causes are numerous, each case having its own 
special aetiology, and it matters not what this may be so the 
“ chill ” occurs. 
The question now arises : What is the nature of the “ chill¬ 
ing ” ? It is of nervous origin, and this brings us down to the 
starting-point of the disease. This “ chill ” has been defined 
as a “ prolonged depression of nerve force without the re¬ 
action which should occur immediately after the collapse.” 
In the case where the “ chill 5 ’ occurs in the horse, the ac¬ 
tion of the cold air on the cutaneous nerves and nerve endings 
has been severe, so severe that for a time the nerve centres 
are paralyzed, as it were, from the number of afferent im¬ 
pulses received, and have lost control over the vaso-motor 
center, so that we find the caliber of the vessels over which 
these minute nerves possess an inhibitory power, constricted 
and carrying less blood than formerly. This condition of 
affairs is followed in a short time by what is termed the “ re¬ 
action,” when the nerve centers, recovering from the shock, 
begin to reassert command over the vaso-constrictor centre, 
and the blood flows again freely through the minute capilla¬ 
ries ; and it is just at this point where the crisis occurs. If 
the action of the cold has not been too depressing in its effect, 
the minute nerves once more take command of the capillaries 
and vessels nearest them, and all goes on well. If, on the other 
hand, the depressing effects have been too severe, these nerves 
are not able to reassume their governing power over the 
walls of the vessels, these consequently lose their tone, so that 
when the blood is pumped into them they become unduly re¬ 
laxed and filled, and because of this the blood flows slowly 
and more slowly until it almost stagnates and we have what 
is termed congestion. 
This is the result of the action of the cold air on the out¬ 
side skin. Now, as we are dealing more particularly with the 
lungs, let us not forget that the mucous membrane lining the 
bronchial tubes and the air cells is continuous with the exter- 
