Inflammation is the most important of all the morbid processes that fall under the notice of the physician or surgeon. The most obvious symptoms or phenomena of inflammation, when it attacks an external or visible part, are pain, redness, heat, and swelling. If a healthy man gets a splinter of wood or any other foreign body imbedded in any fleshy part he begins to experience pain at the part, and this is soon succeeded by redness of the skin. In its early stages the process is known as irritation; but soon, if the foreign body be not removed, the pain and redness increase, and are accompanied by a firm and extremely tender swelling at and around the spot, and a sense of abnormal heat. These purely local symptoms are succeeded, if the inflammation reach a certain degree of intensity, by a general derangement of the vascular and nervous systems, to which various names, such as constitutional disturbance, symptomatic or inflammatory fever, &c., have been applied.
Numerous observers have attempted to trace the exact phenomena of inflammation, by microscopic examination of the transparent parts of animals in which the process has been artificially excited. From observation made on the web of the frog's foot and other transparent parts of animals by Wharton Jones, Paget, Cohnheim, Burdon Sanderson, Ziegler, and many others, the main features of the process are now well known.
In inflammation of moderate severity the blood-vessels of the part are seen to dilate, and the current of blood through them, at first sometimes a little accelerated, becomes much slower than the normal. In consequence of this retardation the white blood-corpuscles, being somewhat sticky in consistence, fall out of the central stream, and drag along the sides of the vessel, where, as the inflammation increases, they are arrested. Then follows the most remarkable part of the process. Minute buds are seen to form on the outside of the walls of the veins and capillaries, each one corresponding to a white blood-corpuscle in the interior. These buds grow larger at the expense of the corpuscles, which thus pass through the wall of the vessel without any break in its continuity; and the migration continues till the tissue around the vessels is crowded with corpuscles. At the same time an abnormal quantity of fluid exudes through the walls of the blood-vessels, and in part coagulates, forming with the corpuscles what is known as coagulable or plastic lymph. From the capillaries red as well as white blood-corpuscles pass into the tissues. If the inflammation be more intense complete arrest of the flow of blood in the vessels (stasis) takes place.
We may now consider the explanation of the cardinal symptoms of inflammation. The redness depends upon there being more blood than usual in the blood-vessels of the affected part; sometimes also upon the occurrence of hemorrhage in the inflamed tissue. The swelling depends in part upon the distension of the blood-vessels, but mainly upon the effusion of fluids and blood-corpuscles above described. These are termed the products of inflammation; and many changes, some of a reparative nature and others of an injurious tendency, depend upon their presence. The pain may vary from mere discomfort to intense agony. It is probably due to compression of the sensory nerves of the affected part by the dilated vessels, and the exudation. It is often throbbing. There is usually most pain in those parts in which the tension produced by the swelling is the greatest, as in bone, serous and fibrous membranes, &c. The pain occurring in inflammation is always aggravated by pressure, and by this means the physician can often distinguish between inflammatory and non-inflammatory disorders. The heat is seldom so much increased as the sensations of the patient would lead him to believe; it does not rise above the maximum heat of the blood in the interior of the body. This increase of heat depends upon the increased flow of arterial (or highly oxidised) blood to the part.
The blood obtained by bleeding a patient suffering from inflammation of any important organ usually presents a peculiar appearance after coagulation known as the buffy coat (see BLOOD). Another and a more important change in the blood in inflammation is the augmentation of the fibrin, which often rises to two, three, or more times its normal quantity.
The further course of inflammation is much more variable. The most favourable termination is resolution, where the products of the inflammation are gradually removed by the lymphatics, and the tissue returns to its normal state. If the exuded blood-corpuscles accumulate in large amount (suppuration) they form an Abscess (q.v.), and must in general be evacuated before cure can take place. If the inflamed tissue be superficial its outer layers may die and be thrown off (ulceration), leaving a sore which heals by Cicatrisation (q.v.). If the inflammation be severe and extensive Gangrene (q.v.) or mortification may ensue.
In the return to health of inflamed tissues, where neither resolution nor death of the patient has taken place, formation of new tissue is necessary to fill up the gap which is left by suppuration or ulceration. This is effected mainly by the action of the exuded leucocytes present in the 'plastic lymph,' which under suitable conditions becomes gradually organised into fibrous tissue, bone, &c.; but the restoration of the epithelial covering, where a breach in the surface either of skin or mucous membrane has occurred, is effected only under the influence of epithelial cells present at the edge of the gap. The process is essentially similar to the healthy repair of broken bones (see FRACTURE), or incised wounds, though many authorities do not apply the term inflammation to these cases. It is thus that parts recently severed from the body may be sometimes replaced and still live. The success of the Taliacotian operation, by which a new nose is engrafted in the position of that which had been lost, of the operation of injecting a stimulating fluid into cystic tumours, with the view of setting up adhesive inflammation, and of various other surgical operations, essentially depends upon the property of organisation possessed by inflammatory exudation, or closely allied products. Although the organisation of plastic lymph is thus essentially a conservative and reparative process, it leads in many cases to untoward results. Thus, when a serous membrane (e.g. pleura, pericardium, peri- toneum) is inflamed, the exudation between its contiguous surfaces often becomes transformed by the same process into fibrous tissue, forming layers or bands which seriously interfere with the functions of the organs involved (lung, heart, intestine, as the case may be) after the inflammation has subsided. In inflammation of the iris the pupil may be rendered irregular or immovable, or may even be closed up by inflammatory exudation. In endocarditis, or inflammation of the lining membrane of the heart, exudation may be deposited in wart-like masses on the valves, and may thus occasion some of the worst forms of cardiac disease.
The causes of inflammation are very various. Among predisposing causes must be reckoned any condition which lowers the vitality of the whole body, or of any particular part of it. The most obvious exciting causes are mechanical violence, chemical irritants, excessive heat or cold, producing injury of a part of the body which leads directly to inflammation in that part. Less obvious, but not less certain, is the effect of exposure to cold in exciting inflammation of internal organs. But of all the causes the most important undoubtedly, though they have only been recognised within the last three decades of the 19th century, are micro-organisms—bacteria, &c. (see GERM). Besides the numerous specific diseases attended by inflammation of various organs and tissues proved or believed to be due to these bodies, many forms of what is known as simple inflammation—e.g. acute abscess—have been shown to be associated with them. Some authorities go so far as to say that no true inflammation can take place without them; and though this opinion has not been proved, it is certain that almost all the most severe forms of inflammation are characterised by the presence of some form of micro-organism.
The inflammatory diseases of the most important organs are described under their specific names, and, as a general rule, the termination -itis is employed to indicate an inflammation. Thus, peritonitis signifies inflammation of the peritoneum; iritis, inflammation of the iris; &c. Inflammation of the lungs, however, is usually known as pneumonia instead of pneumonitis, and of the pleura as pleurisy instead of pleuritis. See PNEUMONIA, PLEURISY, ENTERITIS (for inflammation of the bowels), PERITONITIS, STOMACH (for gastritis), LIVER (for hepatitis), EYE (for iritis), BRAIN, &c.
It is unnecessary to enter into the consideration of the treatment of inflammation further than to remark (1) that if possible we must remove its exciting cause, which can seldom be done except when the inflammation is external; and (2) that the patient should be placed on a strictly anti-phlogistic regimen (which implies a total abstinence from solid animal food and stimulating drinks, due attention to ventilation, temperature, &c.). Of the direct remedies, one of the most powerful, both for good and evil, is blood-letting, although at present it is rarely used. The medicines chiefly employed are purgatives, preparations of mercury, tartar emetic, and opium; while, as external applications, hot fomentations or poultices (sometimes applications of cold water or ice are preferable), and counter-irritation by means of blisters, sinapisms, setons, &c., are often of service.