ments. The latter are probably living leucocytes which have escaped into the abscess cavity, the former probably leucocytes which have undergone degeneration and death. The liquor puris consists of water, albumen, and salts, of which chloride of sodium is the chief. It coagulates on boiling. Though probably derived in chief part from the exudation of the serum through the vessels, it differs from serum in that it does not coagulate spontaneously. In very acute abscesses the pus contains, besides corpuscles, granular material derived from the rapid degeneration of the tissues, and under some circumstances bacilli and micrococci are found in it when treated by appropriate reagents. If allowed to stand or to decompose in an imperfectly drained abscess cavity, it will be found teeming with the bacteria of putrefaction.

Varieties of Pus.-Pus is variously spoken of as sanious when it contains blood, curdy when portions of coagulated fibrin are seen floating in it, ichorous when of a watery consistency, mucopus when mixed with mucus, and infective when containing micro-organisms. In some instances it has been observed to have a bluish-green color (blue pus), which is supposed to be due to the micrococcus cyaneus.

The Causes of an acute abscess may broadly be said to be those of acute inflammation, and need not again be referred to. The circumstances which induce the inflammatory process to terminate in suppuration may briefly be said to be persistent and long-continued action of an irritant, and such a lowering of the vitality of the tissues and amount of injury (short of their actual destruction and consequent gangrene) as induce stasis and coagulation of the blood in the vessels, and hence preclude the possibility of resolution occurring.

The Symptoms of an acute abscess are at first those of inflammation followed, while pus is forming, by a chill or rigor and by throbbing pain in the part. Pain, however, usually ceases when suppuration is fully established. The local signs, when the abscess is superficial, are pointing, central softening, and when about to burst, a red and glazed appearance of the skin with separation of the cuticle. Deep suppuration is often difficult to detect; deep-seated fluctuation, oedema, sub-cuticular mottling and tenderness on pressure are then the chief signs, and puncture with a grooved needle will clear up any doubt.

Treatment. The chief indications are to remove the pus with as little injury to the tissues as possible, to ensure a sufficient drain, and to maintain the parts aseptic. When it is evident that suppuration must ensue it should be promoted by moist warmth in the form of a large linseed-meal poultice sprinkled

with opium, or hot poppy fomentations. As soon as fluctuation is detected the abscess should be opened by making a free incision in the most dependent part or where it is pointing, of course taking care to avoid blood-vessels or other important structures in the neighborhood. The pus should generally be allowed to flow out of its own accord. To ensure a thorough drain, and to prevent any tension from reaccumulation, the opening should be free and a drainage-tube should be inserted. If the drainage is efficient no harm will ensue if a poultice, the favorite treatment, be applied. But if the abscess is deep and the aperture small, and there is thus danger of the pus becoming retained, antiseptic dressings should be used, as under these circumstances the retained discharge will probably be under some degree of tension and the pus-forming zone inefficient to prevent absorption. Although it is a rule in surgery to open an abscess as soon as fluctuation clearly shows that pus has formed, there are some instances in which this is especially imperative. Thus an abscess should be opened early when it is situated in the perineum, the abdominal or thoracic walls, the sheath of a tendon, under deep fascia or the peritoneum, in the orbit, near a joint, and in the neck if attended by dyspnoea; when obstructing some passage; when caused by the infiltration of urine, fæces, etc.; and when a spontaneous opening would produce deformity.

Hilton's method, as it is called, of opening an abscess, is very useful when the abscess is situated deeply and among important structures, as at the root of the neck or in the axilla. It consists

in making an incision through the skin and fascia, and then working gently in the direction of the pus with a director. As soon as pus presents, a pair of dressing forceps is slid along the groove of the director into the abscess cavity, the director removed, and the blades of the forceps separated so as to stretch the opening and make a free exit for the pus.

The Complications of Acute Abscess are: 1. Hemorrhage from the involvement of a large vessel. 2. The implication of some important part, as the peritoneal cavity, the interior of a joint, 3. Degeneration into a sinus or fistula. 4. Blood poison

etc.

ing (sapræmia, pyæmia).

CHRONIC ABSCESS.-The process by which a chronic abscess is formed is similar to that described under the acute variety. The preceding inflammation, however, is of a chronic character, and the pus is formed slowly, and when deeply seated often without any symptoms of inflammation. A chronic abscess has a tendency to burrow in the tissues, especially in the long axis of the body; and its walls often become condensed and thickened, and lined with a layer of smooth granulations, which give

it a velvety and mucous membrane-like appearance. The pus may be like that from an acute abscess, or thin and curdy. It never contains bacteria before the abscess is opened; but quite recently micrococci and tubercle bacilli have been demonstrated in the pus taken from many chronic abscesses after cultivation in blood-serum. Cause. A chronic abscess is generally formed in connection with dead bone, joint-disease, a caseating lymphatic gland, or tubercular deposit. At times no cause can be discovered. The symptoms are very various, and differ according as the abscess is found in connection with dead bone, a diseased spine, etc., and will be again referred to under the head of suppuration in bone, psoas abscess, etc. Here it may be stated generally that the chief signs are a fluctuating swelling, often unattended with any sign of inflammation, and the presence of some affection, as spinal caries, that is known to be often associated with abscess. Before a chronic abscess is opened there are usually no constitutional symptoms; but subsequently hectic fever or lardaceous disease of the viscera is very liable to ensue and terminate fatally from exhaustion, renal disease, diarrhoea, or hepatic mischief. Diagnosis.-A chronic abscess may be mistaken for a fatty tumor, a hydatid or other cyst, a blood extravasation, or a soft sclid tumor, and it may be quite impossible to arrive at a correct diagnosis without puncture with a grooved needle. The diagnostic point between these affections will be further alluded to in the section on diseases of regions. Terminations. A chronic abscess, after remaining quiescent for a long period, may take on increased action, and burst either externally, or into a mucous canal, a serous cavity, etc.; or the watery portions of the pus may be absorbed, leaving behind a caseous mass, which may either dry up or undergo calcification; or it may remain in its caseous state for years, and then break down, and set up fresh inflammation around, and produce what is called a residual abscess. Treatment.-Small chronic abscesses unconnected with diseased bone, joints, etc., may be treated like other abscesses by free incision, drainage, and prevention of putrefaction. Large abscesses, especially when the result of spinal disease, require very careful management. If free drainage and antiseptic precautious are neglected, and the pus is allowed to undergo putrefaction, long-continued suppuration, and attending hectic, generally follow and frequently terminate fatally. Hence, many advise that the opening of a chronic abscess should be delayed as long as possible-i. e., until it is evident, from the reddening of the skin, and its near approach to the surface, that it will, if left longer, burst spontaneously. The objections to this plan are, that the evil day is only postponed, and that in the

meantime extensive destruction of the tissues is taking place as the abscess is allowed to enlarge. The best plan would appear to be to aspirate the abscess frequently so as to reduce its size, and then to open it freely with antiseptic precautions, and ensure thorough drainage subsequently. Aspiration alone, however, will in some cases suffice, the abscess drying up, and in this way becoming cured. When the abscess is lined with a thick layer of caseous pus, healing will be promoted by well rubbing the walls with a strong solution of chloride of zinc. The unhealthy granulations in strumous abscesses may be scraped away with a Volkmann's spoon.

DIFFUSE SUPPURATION may occur either, 1, in the substance of the tissues or organs; or 2, on the surface of the skin or a mucous or a serous membrane. As examples of the former may be cited cellular, and cellulo-cutaneous erysipelas, in which, as the result of a spreading infective inflammation, extensive suppuration occurs through large tracts of the subcutaneous tissue; as examples of the latter, gonorrhoea, bronchitis, and some forms of peritonitis. The pathological process in both is practically similar, only that in one the inflammatory products (pus) are dif fused through the tissues, and in the other, over the free surface. Suppuration on the free surface of the skin or mucous membrane when the deeper layers of these structures are involved, is, however, spoken of generally as ulceration; and when the epithelial layers only are affected, as intertrigo in the case of the skin, and as purulent catarrh in the case of a mucous membrane.

Constitutional Effects of Long-continued Suppuration-Hectic Fever and Lardaceous Disease.-HECTIC FEVER is a common accompaniment of prolonged suppuration from whatever cause when the wound cannot be kept aseptic and efficiently drained. It has been ascribed to the drain on the system owing to the formation of large quantities of pus; but this is certainly not the only cause, as a chronic abscess may attain a very large size, and exist for years unattended by hectic as long as it remains unopened; nor after opening does hectic occur if the pus can be prevented from undergoing putrefactive changes, and the cavity can be well drained. It would therefore rather appear to be due to a chronic blood poisoning, consequent upon the absorption of the products of putrefaction in small quantities at a time. Symptoms.-Hectic fever is characterized by profuse sweating, rapid wasting, nocturnal rises of temperature with morning remissions, and generally by diarrhoea and deposits of urates in the urine. The face is pale and pinched, the cheek flushed, the eye bright, the pupil dilated, the tongue red and dry at the edges, and the pulse rapid, small, and weak. The appetite grad

ually fails, the patient becomes weaker and weaker, and dies. exhausted of diarrhoea, lardaceous disease, etc. Treatment.The cause of the suppuration should be removed, or, if this is impossible, the absorption of septic products should be as far as is practicable controlled by establishing a free drain to the suppurating cavity, and by preventing by the use of antiseptics the putrefaction of the discharges. At the same time the system must be supported by nourishing diet and stimulants, and the sweating combated by dilute sulphuric acid, and the diarrhoea. by opium, catechu, or other astringents.

LARDACEOUS DISEASE is another of the complications that may follow prolonged suppuration consequent upon long-standing disease of the bones or joints. As the disease, however, perhaps falls more often under the notice of the physician than of the surgeon, the student, for a description of it, is referred to a work on medicine.

SINUS AND FISTULA.

When an abscess opens spontaneously, or is opened artificially, we have seen that the cavity usually fills up with granulations. Under some circumstances, however, as when an abscess is connected with dead bone, or contains a foreign body, or is formed in connection with a mucous canal or secreting gland, or its walls after opening are prevented from remaining in contact by muscular action, the abscess does not close, but degenerates into a suppurating track called a sinus or fistula. Though the terms sinus and fistula are often used synonymously, the former is generally applied to such a track when it is only open at one end, the latter when it is open at both ends. Although, perhaps, a sinus or fistula more often owes its origin to the non-closure of an abscess, and is hence described here, it may be the result of a wound, of ulceration, of sloughing, or of a congenital defect. Special forms of fistulæ, as fistula in ano, recto-vesical, salivary fistula, etc., will receive special notice under diseases of organs. Here it may be said generally that a sinus, and in some instances a fistula, is a long and often tortuous suppurating track, lined by a false membrane, and usually opening in the midst of prominent granulations. Treatment.-The cause should be sought, and if possible removed, and the walls of the sinus then pressed together by careful bandaging. The bandage should be so applied as to prevent the accumulation of pus in the deeper end, and the consequent reconversion of the sinus into an abscess. If this is found impracticable, a drainage-tube should be inserted and shortened daily as the sinus gradually fills up from the bottom. When the sinus has existed long, and the walls are callous and indurated, it should be stimulated by injections of