toxins produces the exudation, and anemia due to the mass outgrowing its own blood-supply is the cause of the caseation. First, there forms from granulation-tissue a cheesy matter, which is liquefied into scrofulous, curdy, or tubercular fluid. This really is not pus, as the tubercle bacillus is not pyogenic; if true pus forms, it is because of a secondary infection with pus cocci-an accident, and not a part of the natural process of formation of a cold abscess. A cold abscess may be absorbed, or may become encapsuled by densely fibrous organization of its limiting-wall into a thick pyogenic membrane. The fibrous wall of a tubercular abscess is lined by a thin, yellowish membrane, which is studded with miliary tubercles (Volkmann's membrane). Tubercular matter rarely invades a muscle, whereas syphilis often attacks muscle (Warren).

The

Symptoms. The term cold abscess is employed for a tubercular abscess because it presents no inflammatory signs. There is no local heat; no discoloration unless pointing occurs; the parts look paler than natural; pain is absent in the abscess, though it may exist at the point of origin of the fluid; the tubercular material often wanders from its point of origin under the influence of gravity; fluctuation is present unless thick walls mask it. Constitutional symptoms are trivial or absent unless secondary infection occurs. swelling may suddenly appear in some spot-the groin, for instance. When it appears suddenly it has travelled from a distant and older area of disease. The abscess may last for years without producing pain or annoyance. The tubular exploring-needle will settle the diagnosis. The constitution is invariably below normal because of the tubercular infection, and the temperature is a little above normal. A cold abscess which is infected with pus organisms exhibits great inflammation, and septic fever rapidly develops. In tubercular disease of the vertebræ the fluid may find its way to the lumbar region, to the iliac region, or to the immediate neighborhood of Poupart's ligament, above or below it.

Tubercular Abscesses in Various Regions.-Tubercular abscess of the head of a bone (Brodie's abscess) arises in the cancellous structure of a long bone, most often in the head of the tibia. Pain is continued but not usually very severe, is of a boring character, and is worse when the patient is in bed. Attacks of synovitis arise from time to time in the adjacent joint. There is no such thing as an acute abscess of bone. A pyogenic inflammation of such severity that it would cause an acute abscess in soft parts, in bone

causes acute necrosis. The organism obtains access to the bone by means of the blood, and finds in the bone a point of least resistance.

Retropharyngeal or postpharyngeal abscess is usually due to caries of the cervical vertebræ, but can arise in the connective tissue of the parts or as a tubercular adenitis. An abrasion of the mucous membrane may admit the bacilli to the tissue or the glands. A swelling projects from the posterior pharyngeal wall, and there is great interference with respiration and deglutition. Caseous matter from caries of the cervical vertebræ may reach the posterior mediastinum by following the esophagus, or it may appear in front of or behind the sternomastoid muscle (Edmund Owen).

Dorsal Abscess.-The tubercular matter in dorsal abscess arises from dorsal caries, flows into the posterior mediastinum, and reaches the surface by passing between the transverse processes. The tubercular matter from dorsal caries may run forward between the intercostal muscles or between these muscles and the pleura, pointing in an intercostal space at the side of the sternum or by the rectus muscle. It may open into the gullet, windpipe, bronchus, pleural sac, or pericardium. It may descend to the diaphragm and travel under the inner arcuate ligament to form a psoas abscess, or under the outer arcuate ligament to form a lumbar abscess. A psoas abscess points external to the femoral vessels, a characteristic which distinguishes it at once from a femoral hernia.

Iliac abscess arises from lumbar caries, the swelling lying in the iliac fossa and pointing above Poupart's ligament.

Psoas abscess is usually due to lumbar caries, the fluid pointing in Scarpa's triangle external to the femoral vessels. A psoas or iliac abscess, by following the lumbosacral cord and great sciatic nerve, forms a gluteal abscess. These abscesses may open into the bowel, bladder, ureter, or peritoneal cavity.

Lumbar Abscess. In a lumbar abscess the fluid produced by dorsal caries descends beneath the outer arcuate ligament, or the fluid from lumbar caries which collected anterior to or in the quadratus lumborum muscle passes between the last rib and iliac crest in the triangle of Petit, the small space bounded by the crest of the ilium, the posterior edge of the external oblique muscle, and the anterior edge of the latissimus dorsi muscles.1

1 For a lucid description of these abscesses see Owen's Manual of Anatomy, from which much of the above is condensed.

Chronic abscess of the breast is a caseated area of tuberculosis of the breast. A lump is detected which slowly enlarges and finally ruptures, sinuses being formed. The axillary glands are apt to be implicated. The patient belongs to a tubercular stock, as a rule gives a history of previous tubercular troubles of various sorts, and has usually borne children. Chronic abscess of the breast causes little or no pain.

Treatment. If a small cold abscess exists in a superficial structure, open it with aseptic care, rub its walls with bits of gauze to remove tubercular masses, irrigate with 1: 1000 mercurial solution, pack with iodoform-gauze, and dress antiseptically. When the discharge becomes thin and scanty the packing can be dispensed with. If it be slow in healing, inject or swab out with a stimulating fluid as in acute abscess, or inject with iodoform emulsion.

Chronic Abscess of Bone.-Make an incision to bare the bone. Open the abscess with the trephine, the gouge, or the chisel; curet with a sharp spoon and gouge; cut away the edges of the bone with rongeur forceps; irrigate the cavity with hot corrosive sublimate solution (1 : 1000), and swab it out with gauze wet with pure carbolic acid; pack with iodoform gauze and apply dry antiseptic dressings. It is better not to employ an Esmarch apparatus. Bleeding will not be severe, and when no apparatus is used we can be sure that all the diseased bone has been removed, because sound bone bleeds and dead bone does not.

Cold Abscess of Lymphatic Glands.-In non-exposed portions of the body the capsule should be incised and dissected or scraped away, and the cavity swabbed out with pure carbolic acid and packed with iodoform gauze. If the abscess is allowed to burst, it will make an ugly scar; therefore in exposed portions of the body an effort should be made to prevent a scar. When only a little caseated matter exists and the skin is not discolored, prepare the parts antiseptically and carry a silk thread by means of a needle through the skin, through the gland, and out at its lowest point. Dress with gauze. In three days the thread can be taken out and a firm compress applied. When the gland is almost entirely broken down and the skin above it is purple and thin, insert a hypodermatic needle through sound skin into the abscess, draw off the pus, and inject iodoform emulsion (10 per cent. of iodoform, 90 per cent. of glycerin or olive oil). This procedure is to be repeated when pus again accumulates. By this means we can often effect a cure in

a week or so. When an abscess breaks or is at the point of breaking cut away all purple skin, curet the abscesswalls (the abscess having become a scrofulous ulcer), remove the remains of gland and capsule, swab the cavity with pure carbolic acid, and dress with iodoform and corrosive gauze.

Tubercular glands ought to be extirpated before they caseate and form abscess.

Cold Abscess of Mammary Gland.-Many operators simply incise, curette, pack with iodoform gauze, and dress antiseptically. It is wiser to remove the entire gland and clean out the axilla, in order to prevent both recurrence and dissemination.

Large Cold Abscesses (Psoas Abscess).—In view of the facts that these abscesses may cause no trouble for years and that an operation may be fatal, some eminent surgeons are opposed to an operation unless the abscess is moving toward inevitable rupture or is disturbing the functions of organs by pressure. Most practitioners believe, however, that this mass of tuberculous matter is a source of danger through being a depot of infective organisms which may overwhelm the system, and that death will rarely occur in the hands of the operator who employs with intelligence strict antisepsis. In no other cases is attention to every detail more important, as a mixed infection can easily take place, and will probably mean death.

In many cases aspiration can be employed to empty the cavity, injecting either a 10 per cent. iodoform emulsion to the amount of 3iij, or 3iij of a 5 per cent. ethereal solution of iodoform after the fluid is sucked out. After injecting the emulsion squeeze and manipulate the fluid into every nook and cranny. The American Text-book of Surgery advises the injection of from 1 to 3 ounces of the following preparation iodoform, 10 parts; glycerin, 20; mucil. gum Arab., 5; carbolic acid, 1; water, 100.

Whatever fluid is chosen, the operation must be repeated three or four times at intervals of four weeks. It is dangerous to inject large amounts of iodoform, as poisoning may be produced (p. 27). Some surgeons incise such an abscess, inject iodoform emulsion, and sew up without drainage. Such a procedure often fails and is sometimes followed by iodoform-poisoning. If aspiration and injection fail, open, under rigid antisepsis, the most dependent portion of the abscess, scrape its wall with bits of gauze, and over-distend with a 1:1000 solution of warm corrosive sublimate. Let

the mercurial solution run out and then irrigate the cavity with hot normal salt solution, which will remove the remains of the corrosive fluid. With a long probe find the highest point of the cavity, and make a counter-opening; scrape well, search for and remove carious bone, flush out the whole area with corrosive sublimate, wash out the meicurial solution with hot normal salt solution, inject emulsion of iodoform, and either make tube-drainage from opening to counter-opening and from bone to counter-opening, or pack the entire cavity with iodoform gauze. If hemorrhage is severe, after injecting with hot salt solution the cavity must be packed. When a large abscess breaks of itself, it should at once be drained and asepticized as above. In the treatment of a cold abscess give nutritious food, cod-liver oil, quinin, iron, and the mineral acids. Removal to the seaside is often indicated, and mechanical appliances may be needed for diseases of the bones and joints. If secondary infection does occur, the patient develops hectic fever (q. v.).

Dorsal abscess and lumbar abscess are treated after the same plan as psoas abscess, although one incision only is usually necessary unless the fluid has travelled to a distant point.

A postpharyngeal abscess must not be opened through the mouth. To open it in this manner puts the patient in danger of suffocation by fluid running into the larynx during or after the operation. Further mixed infection of the abscess-area will be certain to ensue. Septic pneumonia will be apt to arise from inhaled infected particles, and profound gastro-intestinal disturbance will be liable to develop because of the inevitable swallowing of purulent, putrid, and tubercular masses. Incise the neck and open by Hilton's method, going through the sternocleidomastoid muscle or behind it. Rub the wall with bits of gauze, remove any loose bone, irrigate with hot normal salt solution, inject iodoform emulsion, insert a tube or pack with iodoform gauze.

VII. ULCERATION AND FISTULA.

An ulcer is a loss of substance due to necrosis of a superficial structure. The action of the pus organisms is the same as in an abscess. A broken abscess becomes an ulcer, and an ulcer is a half-section of an abscess. The floor of an ulcer consists of granulation-tissue and corresponds with the abscess-wall. An abscess arises from molecular death within the tissues; an ulcer, from molec