parts of oil of copaiba and castor oil; or paint on a protective coat of flexible collodion.

When the skin seems on the verge of breaking, paint it with a solution of nitrate of silver (gr. xx to 3j). When the skin breaks, a good plan of treatment is to touch once a day with silver solution (gr. x to 3j) and cover with zincichthyol gelatin. We can wash the sores daily with 1: 2000 corrosive-sublimate solution, dust with iodoform, and cover with soap plaster, with lint spread with zinc ointment, or with dry aseptic gauze. When sloughs form, cut most of them off with scissors after cleaning the parts, slit up sinuses, and use antiseptic poultices. In sloughing Dupuytren employed pieces of lint wet with lime-juice and dusted the sore with cinchona and charcoal. In obstinate cases use the continuous hot bath or the intermittent ice poultice. When the sloughs separate, dress antiseptically or with equal parts of resin cerate and balsam of Peru. If healing is slow, touch occasionally with silver solution (gr. x to 3j). Bed-sores, being expressive of lowered vitality, demand that the patient shall be stimulated, shall be well nourished, and shall sleep soundly.

Postfebrile Gangrene.-Dry or moist gangrene may follow any fever, but is most frequent after typhoid (may follow influenza, measles, scarlet fever, etc.). Keen, in the Toner lecture for 1876, collected 113 cases of postfebrile gangrene, and 43 of these were due to typhoid. It is most usual in the lower extremities, but may appear in the upper extremities, cheeks, ears, nose, genitals, lungs, etc. Some writers have assigned as the cause weakness of cardiac action, but most observers believe an obstructing clot is the usual cause. This clot is secondary to endarteritis due to toxins of the typhoid bacillus.' It most often appears in the third week, but may arise far into convalescence. Treatment presents nothing exceptional. If an extremity is extensively involved, await a line of demarcation before amputating.

Rules when to Amputate for Gangrene.-In dry gangrene, due to obstruction of a non-diseased artery, wait for a line of demarcation. In senile gangrene, if it affect only one or two toes, let the dead parts be cast off spontaneously. If a greater area is involved or the process spreads, amputate above the knee without waiting for the line. In ordinary moist gangrene wait for a line of demarcation. In traumatic spreading gangrene amputate at once. In hospital gangrene and in Raynaud's gangrene wait for a 1 Mettler, in New York Med. Jour., March 9, 1895.

line of demarcation. In diabetic gangrene amputate at once, high up. In ergot gangrene, in postfebrile gangrene, and in frost gangrene wait for a line of demarcation.

IX. THROMBOSIS AND EMBOLISM.

Thrombosis is the antemortem coagulation of blood in the heart or in a vessel, the coagulum remaining at its point of origin and plugging up the vessel partially or completely. This process is an essential part in the arrest of hemor

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FIG. 35.-Thrombus in the saphenous vein (Green).

rhage; it occurs in phlebitis and arteritis, and affords a frequent basis for embolism. Thrombi may form in the veins, in the arteries, and in the heart. Clotting is due to destruction of white blood-cells, fibrin-ferment being set free, causing the union of calcium and fibrinogen and thus forming fibrin. Thrombosis is more common in the veins than in the arteries, the slow blood-current and the existence of valves favoring the deposit, though not causing it. Fig. 35 shows thrombosis.

Causes of Thrombus.—The essential cause of all intravascular thrombi is damage to the endothelial coat, though many other conditions favor their formation. Among these favoring conditions are retarded circulation in tuberculosis, influenza, and fevers, the blood clotting behind the veinvalves after the endothelium has been damaged by toxins; or the pressure of a bandage or of a splint; varicose veins; ligation of a vessel; injuries of a vessel; foreign bodies in a vessel; atheroma in arteries; sutures in a vessel; certain diseases, such as gout, typhoid fever, pregnancy, and septic processes; phlebitis or arteritis arising in the vessel or from extension of surrounding inflammation; and entrance of specific organisms.

It has been asserted that so long as the endothelium of a vessel is uninjured a clot does not form. Slowing of the blood-current in aseptic conditions, it is now taught, will not cause thrombosis. One of the functions of the endothelial coat is to keep the blood fluid by preventing corpuscular disintegration. A thrombus can form only when fibrinferment is set free, and fibrin-ferment can be set free only when white corpuscles disintegrate. When moving blood

coagulates, the third corpuscles first settle out, and then the leukocytes. This is known as the white or "antemortem " thrombus-the clot of moving blood. Thrombi from moving blood are rarely pure white: they contain some red corpuscles, forming mixed thrombi. The red thrombus plugs vessels which are cut across or ligated; it also occurs in septic processes, and is formed after death. A thrombus may be absorbed, first embryonic tissue and then fibrous tissue replacing it (organization). A thrombus may degenerate and break down (fatty degeneration), giving rise to emboli. A thrombus may calcify or may undergo purulent liquefaction, infective emboli being set free. A thrombus in an artery is apt to extend to the first collateral branch, but does not pass higher. The blood-current into the branch prevents further extension. Remember this fact when an artery is cut near a large branch. If we simply tie the artery, such a short clot will be formed that the vessel will not be obliterated. Tie not only the artery, but also the branch. A clot in a vein may extend a long distance. The author has seen in a postmortem examination a venous thrombus reaching from the ankle to the vena cava.

Symptoms.-The symptoms are dependent on the seat of the obstruction. An organ or a part of an organ may exhibit functional aberration. The local signs in a vessel accessible to touch or sight are the presence of a clot; if it be an artery, anemia and the absence of pulse below the clot; if it be a vein, swelling and edema below it. There is usually pain at the seat of trouble, and anesthesia below it. Moist gangrene may follow venous thrombosis, and dry gangrene arterial thrombosis. Thrombophlebitis is inflammation. of a vein in which a septic thrombus forms. We see this condition sometimes in the lateral sinus of the brain as a result of suppuration in the middle ear; in any of the cerebral sinuses after compound fracture of the skull; and in the uterine veins in puerperal sepsis. It is the first step in pyemia. Thrombo-arteritis is inflammation of an artery in which a septic thrombus forms or in which a septic embolus lodges. It occasionally attacks an aneurysmal sac.

Treatment. If in a limb, raise the limb a few inches from the bed, keep it perfectly quiet to avoid detachment of fragments (emboli), paint with iodin or rub with ichthyol, apply a bandage from the toes up, and place hot bottles around the extremity. The great danger is the formation of emboli, so avoid movements and rough handling. In thrombophlebitis, if the vessel is accessible, tie it above and below the

clot, open the vessel, remove the clot, irrigate, and pack with iodoform gauze. Internally the treatment is stimulant and supporting. Massage is unsafe. In thrombo-arteritis treat as in thrombophlebitis.

Embolism signifies vascular plugging by a foreign body (usually a blood-clot) which has been brought from a distance. Emboli may arise either in the venous or in the arterial system, but lodge only in an artery or in the veins of the liver. The initial thrombus may form upon diseased heart-valves or in a vein. It may be composed of fat, micro-organisms, air, or a portion of a tumor. An embolus is arrested when it reaches a vessel whose diameter is less than its own. It is usually caught just above a bifurcation. When an embolus lodges, it at once partially or entirely obstructs the circulation, and increases in size by thrombosis. A non-septic embolus usually organizes. A soft

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FIG. 36.-Embolus impacted at bifurcation of a branch of the pulmonary artery (Green).

embolus may disintegrate and permit of re-establishment of the circulation. An embolus may cause an aneurysm. A septic embolus breaks down, forms a metastatic abscess, and sends other emboli onward. Fig. 36 shows an impacted embolus.

An embolus is more serious than a thrombus it causes sudden plugging which makes dangerous anemia inevitable, and it may produce gangrene if the collateral circulation fails. In organs with terminal arteries (spleen, kidney, brain, and lung) there is no collateral circulation and embolism causes infarction. The embolus produces an area of anemia; the removal of all propulsion upon the venous blood causes it to flow back and stagnate, and vascular elements exude, forming a wedgeshaped area of red tissue, the embolus being the apex of the wedge. This is known as the "red infarction," and is often seen in the lung. The white infarction seen in the brain and kidney is not due to retrogression of venous blood, but is due to anemia and resulting coagulation-necrosis. A septic embolus causes septic arteritis and a septic infarction, and a septic infarction suppurates and forms a pyemic abscess.

Symptoms. The symptoms depend upon the organ involved. They are sudden in onset, and consist of loss of function which may be permanent or which may be followed

by inflammation or softening. Embolism of the cerebral arteries may cause aphasia, paralysis, or coma. Embolism of the pulmonary artery may cause almost instant death. Embolism of the central artery of the retina causes blindness. Embolism of a large artery of a limb produces symptoms identical with thrombus, except more sudden and decided.

Treatment. The treatment of aseptic embolism depends upon the part involved. In a limb, keep the part warm in order to stimulate the collateral circulation, elevate several inches from the bed, and insist on perfect quiet. Massage is unsafe. If gangrene ensues, await a line of demarcation and amputate. In septic arteritis in an accessible region it would be good surgery to act as in thrombo-arteritis from thrombosis. Unfortunately, such a condition is not often in an accessible region. After an operation upon veins (as the operation for varicocele or for hemorrhoids), after a cutting operation, and after fracture, avoid as much as possible movements or handling, as fragments of thrombus may be detached. Operations upon the rectum may be followed by hepatic embolism and abscess of the liver.

Fat-embolism is an accumulation in the capillaries of liquid fat after injuries of adipose tissue, high tension forcing the fat into the open mouths of veins. Some little fat may get into the blood by means of the lymphatics. Fat-embolism occasionally arises in osteomyelitis, after extensive bruises, crushes, or lacerations, and after amputations, fractures, resections, or rupture of the liver.' This fluid fat accumulates especially in the capillaries of the lung and brain.

Symptoms.-The symptoms are those of edema of the lungs and exhaustion, often with coma or delirium. There are restlessness, dyspnea, rapid pulse and respiration, and low temperature. If life is prolonged a day or two, oil is found in the urine. Small amounts of oil may be found in the urine after serious injuries or operations when no symptoms of embolism exist. Nevertheless, the presence of the oil is always an ominous sign, and is often a warning. These symptoms never occur until at least twenty-four hours after the accident, and rarely before the third day. The symptoms occur at a later period than those of shock, and at an earlier period than those of ordinary embolism of the lung. Severe cases are commonly fatal; milder cases are often recovered from.

Treatment. The treatment consists of the ordinary methods used in shock-stimulants, heat, etc., with dry cupping

1 G. H. Makins, in Heath's Dictionary.