An abscess; (from abscedo, to depart;) or from abs and cedo, to retire.) A cavity containing pus, or a collection of matter in a part. So called, because the parts which were joined are now separated; one part recedes from another, to make way for the collected matter. Termed also Diapyema ; dubletus, an Arabic term; and exi-lura.

and used by Hippocrates, are translated by Celsus, abscessus, and sometimes vomica. Paulus Aegineta seems to limit the signification of abscessus to suppuration, by defining to be an abscess, or a corruption of the fleshy parts, muscles, veins, and arteries.

The words and which signify to recede or retire, are used by Hippocrates with great latitude. He means by them any critical removal of offending humours, however discharged ; also the change of one disease into another, as a quincy into a perip-neumony, etc. See Apostasis. But the present practice seems universally to consider an abscess as that tumour which follows an inflammation, for almost every abscess is the consequence of inflammation.

The proper seat of abscesses is the cellular membrane.

The source of the purulent matter in abscesses is not yet determined. It has been supposed, with some appearance of reason, to be derived from a solution of the solid parts in the exuding serum; and experiments, made by digesting animal substances in serum, have been adduced as supporting this opinion. On the other hand, it has been contended, particularly by De Haen, that purulent matter may be formed without suppuration, without a destruction of the solid parts, or previous inflammation; and it is certain that membranes will, at times, assume a purulent appearance, where little or no previous inflammation has taken place : in such cases, the appearance of pus has been attributed to a change in the state of the extreme vessels, by which they have become secretory organs separating a peculiar fluid. It is also certain, that purulent matter may be distinguished, chemically, from other fluids of the body ; and microscopical observations show it to be composed of spheroidal particles, swimming in a fluid. It is, however, evident, that pus is in very few instances, if ever, produced without destruction of the solid parts, which are lost in the fluid discharged; and that new granulations of flesh arc formed under its protection. If it destroys the animal substance, it contributes to its reproduction : it regenerates instead of corroding. In this place, however, we speak of mild purulent matter; in the language of surgery, laudable pus ; the formation of which we shall afterwards attempt to explain. See Inflammation, Malignant Ulcer, Cancer, and Hectic.

The inflammatory heat continuing to increase, in opposition to the usual means, a suppuration will certainly follow. If the patient feels frequent shiverings, a formation of pus is probably commenced. This shivering is produced by the absorption of some of the pus, or its thinner parts; but when the matter is enclosed in a cyst, or surrounded by an inflamed surface, this absorption rarely or never happens. Whatever be the source of the pus, as it must be derived from the vessels, their tension is removed, the many blood-vessels which before were compressed are freed, the blood circulates freely, the heat abates, and the part is less red, but gradually becomes more soft.

In the progress of an abscess on the external parts, the tumour increases, as well as its heat, pain, and redness: a pulsation i: perceivable in the tumour, and an evening hectic comes on. The pain and tension then cease, the hardness of the part at length yields to the touch, and the skin bursting, gives a vent to the contained matter.

An abscess should be carefully distinguished from a hernia, an aneurism, and from a varicous tumour.

A hernia, as will appear hereafter from its seat, its effects, and the absence of pulsation, cannot easily be mistaken for an abscess: and a varicous vein, as it is neither attended with heat, with pulsation, nor fever, can scarcely ever lead the practitioner into error. An aneurism may be supposed to be an abscess; or, on the other hand, an abscess may be mistaken for an aneurism, as each may be attended with inflammation or pulsation. The practitioner, however,- who finds a painful tumour beating strongly, if in the course of a large artery, Mill carefully attend to the previous symptoms. Has much fever preceded ? has no violent strain occasioned it ? can the finger be passed between the tumour and the artery? It is then an abscess. Has the tumour increased slowly, without fever, come on from strong exertion; and does the pulsation, on pressing between it and the artery, appear more evident? It is then aneurism: but to this subject we shall return. See Aneurism.

If, during the treatment of an abscess, the patient is sleepless and feverish; if he breathes with difficulty and loathes his food; if the pus when discharged, is ill-coloured, fetid, and sanious; if blood or spongy flesh appears in the cavity of the ulcer; if faintings come on during or after the times of dressing; the prognostic is unfavourable: on the contrary, if these symptoms are absent, or but in a moderate degree, a favourable issue may be expected. By improper treatment an abscess is easily converted into a,mortification. "Deep-seated abscesses are sometimes difficultly discovered by the touch; but as no considerable suppuration can happen in the body without being soon after accompanied with a hectic fever, the slightest appearance of this fever at once determines the case.