The coexistence of the phenomena, redness and heat, with swelling and pain, the ordinary symptoms of inflammation, may, therefore, be considered as sufficient evidence of the presence of the inflammatory condition. The absence, however, of one or more of these phenomena is not incompatible with the existence of inflammation, for the increased redness and heat may disappear before the inflammatory process ceases, and pain be sometimes absent.

The redness of an inflamed part is usually the first observable phenomenon, and one of the most characteristic symptoms of inflammation, and one also that is persistent and due to hyperemia. It varies in intensity, according to the degree of the inflammatory process, the nature of the part affected, the condition of the system, the cause of the inflammation, the freedom from obstruction in the vessels, and the rapidity of the circulation. Of a light tint in the early stage, it becomes deeper as the inflammatory process increases in degree, until every grade, almost, of redness is observable, ending in a deep crimson or even purple. It may appear in points, streaks, in minute ramifications, or be quite uniform over the entire surface affected. Usually it is more intense in one spot, gradually fading as it recedes, until lost in the surrounding healthy tissue; in other cases the redness has an abrupt boundary, and is of equal intensity over its entire area. The bright hue usually attends ordinary active inflammation; the dark or purplish hue that form of inflammation proceeding from some specific cause, or associated with a gangrenous tendency, and indicates stasis. The redness of inflammation is caused by the increased amount of blood entering the vessels of the part, and remaining there for a longer time than is natural under other conditions.

The Heat of an inflamed part is also caused by the unusual quantity of red blood present, and also by an increase of that vital action upon which the evolution of heat depends, namely, super-oxidation of the affected tissues, resulting in their decomposition. It is more marked at the focus of the inflamed area. The increase of temperature is generally more sensible to the sufferer than to the observer, though it may often be detected by the hand, and is very evident by the use of the clinical thermometer; it is also verified by comparison with other unaffected parts; but is never beyond the temperature of the internal organs.

The Swelling of an inflamed tissue is caused in part by the unusual quantity of blood present in the dilated vessels, - the engorgement of the blood vessels of the part, and also by the matters, both liquid and solid, which exude into the affected tissue through the walls of the dilated vessels, and also to extravasation resulting from rupture of these walls; for as the vessels are distended their walls become thinner, and permit the blood plasma to escape through them in greater quantity than is required for mere nourishment; hence the inflamed tissue becomes infiltrated with this plasma, the consequence of which is an increase of thickness or swelling. The swell of a part, however, without other symptoms is not an evidence of inflammation, as this phenomenon may occur from other causes. Swelling may also be absent when the other symptoms of inflammation are present, an example of which is afforded in inflammation of mucous membranes, before exudation has occurred in the connective tissue beneath. The swelling is soft in acute inflammations, and hard in the chronic form, being especially marked in loose connective tissue.

The Pain of inflammation, which is persistent, and increased by pressure, motion, or exercise, is mainly due to mechanical pressure upon the nerve-filaments; and exercise increases the arterial tension and augments the pain. Every tissue is supplied with sensory nerves, and the pain resulting from irritation and injury varies considerably, in accordance with the nature of the part and its supply of nervous filaments. Parts having little sensibility in a normal condition, often become extremely painful when inflamed; the gums afford a well marked example. When the parts are unyielding, as in periodontitis, the pain becomes very severe; and a pulsating or throbbing pain is caused by the increased force of the smaller vessels conveying the blood to the focus of inflammation, and also the obstruction of the circulation produced by the swelling and increased by the stasis at the focus of the affected area. When the veins of an inflamed part become obstructed by the swelling, bringing about pressure to such a degree as to prevent the blood from passing through them, the quantity being constantly increased by the supply from the arteries, a condition of strangulation results, in which the pain is very severe.

We find an example of this condition of strangulation in pulpitis, or inflammation of the pulps of the teeth. Pain is also generally present, even in the case of soft tissues affected with inflammation, and where every advantage is afforded for their swelling; the oral mucous membrane is an example. There is also pain of an itching character, in certain forms of inflammation of mucous membranes; also boring pain in the neighborhood of joints. The pain of alveolar abscesses, when they slowly form, is often of a tensive character, and generally becomes lancinating when they are about to point; and in all such cases is useful in determining the seat of the suppurative process. At times the pain is reflected to parts remote from the seat of inflammation, as otalgia in pulpitis, etc.

The acute form of inflammation may change to the subacute and finally to the chronic, examples of which are presented in the different stages of pulpitis and periodontitis. The constitutional symptoms of acute inflammation are sthenic and asthenic fevers: the sthenic being characterized by full, strong, rapid pulse, increased temperature, flushed face, injected conjunctiva, headache, lumbar pains, interrupted sleep, diminished secretions, dark colored urine, thirst, tongue coated white or yellowish, and constipation; and is common in the strong and robust.

Asthenic fever is characterized by a feeble pulse, a fluctuating temperature, a dull, torpid, and at times delirious mental condition, the tongue dry and coated with a brown or black fur ; and is common in the very young and feeble and old persons.

The fever of inflammation, also known as "traumatic," is very generally present when the inflammation is severe, or the injury occasioning it is extensive and complicated. This inflammatory fever generally makes its appearance in from twelve to twenty-four hours after the injury is received, or when the inflammatory process is at its height; and when the parts have previously been healthy, and the inflammation limited, it is moderate in its character and soon terminates spontaneously. This fever is indicative of the introduction into the system of poisonous substances resulting from the pathological changes in the exudates or the fixed tissue cells, on account of the action of the specific microorganisms. The symptoms of inflammatory fever are a feeling of fatigue, restlessness, thirst, hot and dry mouth, coated tongue, urine scanty, but deeper in color, frequent pulse, temperature about 100° F.; and the fever usually reaches its climax in about thirty-six hours, when it begins to decline, and by the sixth or seventh day has disappeared. In the case of an abscess, it frequently happens that when suppuration occurs the fever begins to decline. Should the fever continue longer than the time referred to, the cause may generally be due to deeper suppuration and other complications of the local affection. During the inflammatory process, when putrescent matter has been absorbed by the blood in greater quantity than can be resisted or gotten rid of by the organism, and there is no escape from it by drainage, the symptoms of inflammatory fever become more intense, and a condition of septic poisoning takes place, known as septicemia. When some time has elapsed after the inception of the inflammatory process, and the characteristic fever has almost disappeared, a chill suddenly occurs, followed by profuse perspiration, the condition known as pyemia is present - pus globules in the blood.