454 ' DISEASES OF THE RESPIRATORY ORGANS. 
improvement. So often has this point been noticed that it 
is almost imjiossible to escape the conclusion, that causes alto¬ 
gether independent of atmospheric temperature are at work to 
occasion the derangements in the system which we are all so 
familiar with in ourselves as well as in our animals. 
The frequency of the occurrence robs the malady of half 
the interest it would otherwise excite; its symptoms, though 
common, are not trifling; nor would the functional and 
organic changes be lightly estimated if they were not so 
constantly under 'our observation. Let us for a moment 
examine the phenomena of a cold as we can recollect them 
to have presented themselves, probably on many occasions. 
A slight sensation of chilliness is probably the first indica¬ 
tion ; and here at the outset we have matter for reflection. 
The ordinary equable temperature of the body, preserved in 
a wonderful way through the medium of the nutritive, respira¬ 
tory, and circulatory functions, is suddenly disturbed by a 
transient shiver, not consequent upon contact with a cold 
medium, but under external circumstances that afford no 
clue to the change. It will not suffice to say that diversion 
of the current of blood from the surface occasions a diminu¬ 
tion of animal heat, as this condition is most likely not pre¬ 
sent; indeed the sudden chill of which we speak is more 
often associated with a very perceptible increase of surface 
heat. The susceptibility of the nervous system will be next 
adduced in explanation; a sudden impression is transmitted, 
say from the extremities of the sensient nerve to the spinal 
centres. Very satisfactory and lucid this ! Here, in the pre¬ 
sent advanced state of physiology and pathology, we have a 
simple fact of common occurrence. A sudden impression of 
cold literally flashes along the spinal cord, without anything 
being present in the surrounding circumstances to account 
for it; the development of animal heat is for a brief space in¬ 
terrupted ; the force of the organism secures a momentary 
shock; and, honestly speaking, we cannot offer an intelli¬ 
gible and simple explanation; meanwhile we are involving 
ourselves in the complicated mazes of pathological inquiry, 
while the shortest and straightest roads are yet unftimiliar 
to us. 
To continue our analysis. The sensation of chilliness may 
continue, or it may not; the patient may suffer from a feeling 
of cold while his friends complain with equal bitterness of 
the heat; symptoms of fever are at the same time evident in 
dry, hot skin, irritable pulse, and injected membranes ; thirst 
is constant, the secretions are diminished, and a sense of 
languor pervades the frame. We ask the pathologist to 
