DISEASES OF THE RESPIRATORY ORGANS. 
455 
pause a little over the consideration of these phenomena^ and 
to endeavour to trace them to their source ; if it will assist 
him^ he is at liberty to suppose that the patient has pre¬ 
viously been exposed to a draught, or has got his feet wet, 
or has been subjected to a sudden change of temperature ; can 
he satisfy his mind upon the question? How does the con¬ 
tact of cold air upon a part of the body, or the presence of 
moisture, or change from a hot room to the cool air without, 
or the reverse, occasion all these functional derangements ? 
We can understand that these causes may lead to local 
changes in the circulation and nervous functions of the parts 
immediately implicated, the skin and mucous membranes, 
and even the internal organs; but to connect them with the 
indications we have adduced is quite beyond our power, and 
the difficulty is largely increased when the symptoms occur 
without the presence of any of the quoted causes. 
During the present time, and for some days past, the tem¬ 
perature of the air has been uniformly hot; no variation has 
been observed, and yet under these seemingly favorable cir¬ 
cumstances catarrh or influenza has been remarkably pre¬ 
valent in man and animals, attacking in many instances 
those who seem proof against ordinary causes, as they are 
presumed to be. 
The result of a candid inquiry into the circumstances 
affecting the prevalence of catarrhal affections will be, we are 
satisfied, to establish a conviction that the received notions 
relative to the causation of these diseases are unsatisfactory^ 
and indeed in the majority of cases untenable j that something 
beyond, and possibly independent of the temperature of the 
air, must be assumed in order to explain the disturbance of 
the system; and lastly, that there is every reason to conclude 
the existence of some subtile material that has hitherto 
escaped observation, of the nature of miasm,’^ which being 
taken into the system, occasions certain molecular changes 
that are expressed by certain symptoms of an intensity pro¬ 
portioned to the quantity of the poison absorbed or the 
susceptibility of the system to its influence. It will be seen 
that this statement brings us again to our primary position— 
the vagueness and uncertainty of our knowledge upon 
the subject of so simple a pathological problem as a common 
cold. 
Fever to some extent attends the progress of the catarrhal 
affection invariably; sometimes the indications are exceed¬ 
ingly slight, at others very decided, and not unfrequently a 
critical evacuation is perceived from the respiratory or digestive 
membrane, in the shape of profuse mucous discharge or 
