out injury. Silk can be used for both ligatures and sutures; many sizes should be kept on hand. Sutures of silk should be well boiled before using. A convenient method of preparation is to wind the silk on a glass spool, place the spool in a large test-tube, close the mouth of the tube with jeweller's cotton, introduce the tube into a steam sterilizer, and keep it there for one hour. These tubes are carried in wooden boxes sealed with rubber corks. Silkworm gut contains fewer bacteria than catgut and does not swell when introduced into a wound. It is a very valuable suture-material, but is not used for ligatures. Silkworm gut is prepared by placing it in ether for forty-eight hours and in a solution of corrosive sublimate (11000) for one hour. It is carried in a long tube filled with alcohol. A few minutes before using the gut is placed in carbolic acid and alcohol (one-third of a 5 per cent. solution of acid, two-thirds of alcohol). Silk and catgut should be tied by the reef-knot. Silkworm gut is tied by the surgeon's knot. The first double knot is double and tight, the second is single and is lightly tied. If the second knot is light, it will not cut (Greig Smith). Silver wire is

prepared by boiling.

Most wounds are closed by interrupted sutures of silkworm gut, but silk, catgut, chromic catgut, or silver wire can be used. The old continuous suture (Glover's stitch) is rarely used. An admirable closure can be effected by Halsted's subcuticular stitch, and scarcely any scar results. Marcy's buried tendon sutures are very valuable, especially in hernia. operations and in various operations upon the abdomen. Kangaroo tendon is the best material for buried sutures. This tendon is prepared by boiling it for one hour in alcohol and then treating it by the palladium process exactly as catgut is treated.

Dressings are made of cheese-cloth. This material is boiled in a solution of carbonate of sodium, rinsed out, and dried; it is then soaked for twenty-four hours in a solution containing I part of corrosive sublimate, 2 parts of table-salt, and 500 parts of water. It is placed in jars, and it may be kept moist or dry.

Sterilized gauze is prepared by boiling the material in soda, rinsing, and either boiling it for fifteen minutes or placing it in the steam sterilizer for the same time.

Iodoform gauze is useful for packing and for dressing foul wounds. It is prepared as follows: make an emulsion composed of equal quantities by weight of iodoform, glycerin, and alcohol, and add corrosive sublimate in the proportion

This mixture stands

of I part to the 1000 of the mixture. for three days. Take moist bichlorid gauze, saturate it with the emulsion, let it drip for a time, and keep it in sterilized and covered glass jars (Johnston). Lister's cyanid gauze (double cyanid of zinc and mercury) is not certainly antiseptic, and must be dipped into a corrosive-sublimate solution (1:2000) before using. All forms of gauze can be bought ready prepared from reliable firms. Some surgeons place silver foil upon a wound before applying the gauze (Halsted, p. 29). Small wounds in which drainage is not employed may often be dressed by laying a film of aseptic absorbent cotton over the wound and applying, by means of a clean camel's-hair brush, iodoform collodion (grs. xlviij to 3j).

When a wound is dressed with gauze a rubber-dam is sometimes laid over the dressings, so as to diffuse the discharge and prevent it from coming rapidly to the surface. The use of the rubber-dam is not nearly so common as formerly. In an aseptic wound dry dressing uncovered by rubber is the most useful. When a dressing is covered by an impermeable material it becomes wet, acts as a poultice, and the discharges on the dressing may undergo decomposition. Drainage is obtained when needed by rubber or glass tubes, by strands of horsehair, silkworm gut, or catgut, or by pieces of gauze. Gauze, catgut, etc., are known as capillary drains. When moist they drain serum excellently, but pus very badly, or not at all. Drainage-tubes or strands are brought out at a portion of the wound which will be dependent when the patient is recumbent. Drainage is used in all infected wounds, in most very large wounds, in wounds to which irritant antiseptics have been applied, and in cases in which large abnormal cavities exist. Dressings must be changed as soon as soaking is apparent, and the change must be effected with all of the aseptic care employed in the operation. Stitches may usually come out about the sixth day. In large wounds only a few of them are taken out at one time, the remainder being allowed to remain for a couple of days longer. When a stitch begins to cut it is doing no good, and it should be removed, no matter how short a time it has been in place.

Preparation of Marine Sponges.-Beat out the dust; place them for forty-eight hours in a solution of hydrochloric acid (15 per cent.); wash them out with water; place them for one hour in a solution of permanganate of potassium (3iij to 5 pints of water); soak for four hours in a solu

tion containing 10 ounces of hyposulphite of sodium, 5 ounces of hydrochloric acid, and 3 pints of water; wash with running water for six hours. Keep the sponges in a jar containing corrosive-sublimate solution (1 : 1000). After using, wash in hot water, soak for half an hour in a solution of sodium carbonate (1: 32), wash in hot water, and replace in corrosive sublimate. A marine sponge inevitably becomes foul in its interior, and should not be used.

Senn's Decalcified Bone-chips.-Take the shaft of the tibia or femur of a recently killed ox, saw it into portions. two inches in length, remove the marrow and periosteum, and place the fragments of bone in a 15 per cent. solution of hydrochloric acid. Change the solution every twentyfour hours. In from two to four weeks the bone will be decalcified. Wash in distilled water, place the pieces of decalcified bone for a few minutes in a dilute solution of potash to neutralize the acid, and then immerse for twenty-four hours in distilled water. The portions of bone are cut into strips in the direction of the long axis of the segments. Each strip is three-quarters of an inch wide and should be sliced into bits one millimeter thick. These chips are kept in an alcoholic solution of corrosive sublimate (1: 500).

III. INFLAMMATION.

Definition.-Inflammation is a nutritive disturbance arising from tissue-damage, and is not an increase of nutrition. It is defined by Sanderson as "the succession of changes which occur in a living tissue when it is injured, provided that the injury is not of such a degree as at once to destroy its structure and vitality." The changes alluded to in this definition comprise-(1) changes in the vessels and the circulation; (2) departure of fluids and solids from the vessels; and (3) changes in the perivascular tissues.

Vascular and circulatory changes are essential to inflammation in both vascular and non-vascular tissues. In the former they occur in the inflamed tissues; in the latter (cornea and cartilage) they are manifest in neighboring tissues from which the non-vascular area derives its nutritive material.

Active Hyperemia.-When an irritant is applied to tissue there may be a momentary arterial contraction due to irritation of the nerves, but this contraction is transitory, and is not an inflammatory phenomenon. The first vascular phenomenon is dilatation of all the vessels-capillaries,

venules, and arterioles-appearing first and being most pronounced in the small arteries. As a result of the dilatation there are increased rapidity of circulation and increased determination of blood to the part, and the area of hyperemia becomes warmer than is normal. This condition of increased circulatory activity is known as "active hyperemia " (Fig. 19).

Active hyperemia is an increase in the amount of moving blood in a part. Passive hyperemia is an increase in the amount of blood in a part,

but not of moving blood, as passive hyperemia or congestion is due to venous obstruction, and the blood is stagnated. Plethora means an increase in the total amount of body blood. Diminution in the amount of blood in a part is ischemia.

In active hyperemia more blood goes to the part and more blood passes through it, an increased amount of venous blood comes from the hyperemic area, the venous tension is increased, and the veins may even pulsate. The capillaries, which under ordinary circumstances contain but few blood-cells (Fig. 18), become filled with corpuscles, and even the smallest capillaries pulsate. The capillaries contain no muscle-fiber, and hence these tubes cannot actively contract, contraction or dilatation depending upon the amount of blood sent to or retained in them. In active hyperemia the increased amount of blood sent to the part causes capillary dilatation. Fluid elements rarely leave the blood-vessels during active hyperemia, but they occasionally do. The wheals of urticaria are thus formed (Warren). Active hyperemia is often the first stage of an inflammation, but it is not of necessity followed by other inflammatory changes, and it can be caused by nerve-section or nerve-stimulation.

During active hyperemia the capillaries are crowded with corpuscles and the blood in the veins is of a much brighter red than in health. The red blood-cells are swept along the

centre of the current (in the axial stream); the white bloodcells float lazily along near the vessel-wall (Fig. 19).

Retardation.-After active hyperemia has existed for a variable time the blood-current begins to lessen in velocity, until it becomes more tardy than in health. This is known as "retardation of the circulation." Retardation is first noted in the venules, next in the capillaries, and last in the arterioles; but arterial pulsation continues. The white cells show a strong tendency to adhere to the vein-walls, and, as a re

sult, accumulate against the inside of, and stick to, these walls and to one another, until the veins are entirely lined with layers of leukocytes. In the capillaries some leukocytes gather, but not many. In the arteries they adhere during cardiac dilatation, but are swept away by the force of the heart's contraction. Retardation is believed to be chiefly due to paresis of the muscular walls of the arterioles. This causation seems probable when we recall Lord Lister's experiments upon FIG. 19.—Dilatation of the vessels in inflammation. the pigment-cells of the frog's foot. Lister proved that inflammation paralyzes the pigment-cells, and concluded that dilatation at the focus of an inflammation is due to the paralyzing action of an irritant. Dilatation at a distance from the focus is a reflex phenomenon (W. Watson Cheyne).

Oscillation and Stagnation.-By this accumulation of leukocytes the blood-stream is progressively narrowed and the axial current is impeded. The red blood-cells begin to stick to one another, forming aggregations like rouleaux of coin, which increase the difficulty the axial current has to contend with, until progressive movement ceases and the contents of the vessels sway to and fro with the heart-beat. This is the stage of oscillation. In a short time oscillation ceases and the vessels are filled with blood which does not move, and the vessel-walls become irregular in outline or