The seat of the disease is in the mucous membrane, which is a
continuation of the external skin, folded into all the orifices of the
body, as the mouth, eyes, nose, ears, lungs, stomach, intestines and
bladder; its structure of arterial capillaries, veins, arteries, nerves,
&c., is similar to the external skin; its most extensive surfaces are
those of the lungs and intestines, the former of which is supposed to be
greater than the whole external surface of the body.
The healthy office of this membrane is to furnish from the blood a fluid
called mucus, to lubricate its own surface, and protect it from the
action of materials taken into the system. The mucous membrane and the
external surface of the body seem to be a counterpart of each other, and
perform nearly the same offices; hence, if the action of one is
suppressed, the other commences the performance of its office; thus a
cold which closes the skin immediately stops the perspiration, which is
now forced through the mucous membrane, producing the discharge of
watery humors, pus intermixed with blood, dry cough, emaciation, &c.
There are two varieties of this disease; the first is called _common
catarrh_, which proceeds from cold taken in pasture that is not properly
drained, also from atmospheric changes; it may also proceed from acrid
or other irritating effluvia inhaled in the air, or from poisonous
substances taken in the stomach in the form of food. The second variety
is called _epidemic influenza_, and is produced by general causes; the
attack is sometimes sudden; although of nearly the same nature as the
first form, it is more obstinate, and the treatment must be more
energetic. It is very difficult to lay down correct rules for the
treatment of this malady, under its different forms and stages. The
principal object to be kept in view is, to equalize the circulation,
remove the irritating causes from the organs affected, and restore the
tone of the system.