All the world knows when a hand, a foot, or an eye is inflamed. Proverbially, the signs of this are redness, heat, pain, and swelling. The redness is owing to the excess of blood ; the heat to the same cause, with also probably some increase of chemical change in the part. Pain is not quite so clearly to be accounted for. Pressure on a nerve is known to cause pain ; and the excess of blood beating on a part at whose centre is stagnation, must induce considerable pressure. Nerve-pain (neuralgia), however, often occurs without inflammation and with-out pressure. Some one has wisely said that pain is always a sign of a tendency in the part towards,death. It is, at least, indicative of lowered vitality, local or general; and that is present at the centre of an inflamed organ, while around it there may be the heightened activity of stimulation. In a boil, and yet more fully in a carbuncle, we see the dead centre (core) of the violent inflammation, when its force is nearly spent.

The swelling of an inflamed part is due in considerable degree to the accumulation of blood in it. But, under the pressure of the heightened circulation, some of the lymph (watery portion) of the blood escapes from the blood-vessels into the substance of the part. This undergoes changes, which are important.

An active or acute inflammation may end in several ways:

1. Resolution is the early passing off of all the inflammatory symptoms, leaving almost no sensible change in the part.

2. Effusion of lymph, not at once absorbed, shows itself in bands which glue together tissues naturally movable, or in a collection of fluid (serum), constituting a form of local dropsy. In an attack of pleurisy, both of these results may follow instead of resolution.

3. Suppuration is the formation of pus ; that is, yellow matter, which is very seldom absorbed, and whose best destiny is to be got out of the body by an opening, natural or artificial, at or near the external surface. Every "gathering" or abscess is an example of this. Pyaemia is a general disorder of the system, with a disposition towards the formation of collections of pus in different organs, with fever and much weakness, endangering life.

4. Mortification, also called gangrene, or sloughing, is the actual death of the part. Frozen feet mortify, not from inflammation, but from the directly killing effect of cold. Inflammation does not often end in mortification ; if it does so, it is either from the extreme intensity of the inflammatory process, or from a very low vital condition of the patient affected.

Inflammation is modified considerably by specific causes of disease. A gouty toe is one example of this ; a wrist or elbow inflamed with rheumatic fever is another. The sore throat of quinsy, that of scarlet fever, and that of diphtheria, are all inflammations, yet each somewhat different from the others. The pustule of vaccination and that of genuine small-pox are not precisely alike; and still different is that of chicken-pox ; and so on with other specific diseases.

Chronic inflammation is not a desirable term, though it is used in all medical books.

In it, redness, pain, or at least soreness, and more or less swelling, are present, in varying degrees ; but there is no effusion of lymph, which really is the characteristic of a true inflammation. Irritability is a usual part of what is called chronic inflammation ; we might often with advantage speak of this in describing the disorder: thus, irritable eyes, irritable stomach, irritable bladder, irritable womb, irritable brain, etc.