pans, allowing two pounds for every thousand cubic feet of space. Set the pans on bricks so as not to burn the floor, pour a little alcohol over the sulphur and ignite, beginning with the pan farthest from the door by which you are to make your exit. Leave the room quickly, and paste up this door like the others. Keep it closed for twenty-four hours; then open all the windows, and let the room air for as much longer.

When chlorine is used, the same precautions must be taken against its escape. The materials for its production are better placed in the higher parts of the room than on the floor, as the gas is heavier than air. The following is the best way to procure it in quantity: Mix an equal bulk of common salt and the black oxide of manganese in a shallow earthen dish, add two pints of sulphuric acid, previously diluted with two pints of water, and stir with a stick.

The efficiency of both sulphur and chlorine is increased by the presence of steam; the latter especially requires a certain amount of moisture in the air.

CHAPTER XV.

Surgical cases-Wounds of various kinds-Their modes of healingInflammation-Blood-poisoning-The treatment of wounds-Surgical dressings—Lister's method-Operations—Giving anæsthetics -Care after operation-Dangers to be anticipated.

WOUNDS of all kinds, with the diseases resulting from them, and such others as are treated by operative or mechanical means, come under the head of surgical cases. A wound is defined as a solution of continuity of the soft parts. It may be of any degree of severity, from a slight contusion to an extensive laceration.

An incised wound is a simple smooth cut, like that of a knife, and is dangerous in proportion to its depth. If the edges are torn the wound is described as lacerated. A lacerated cut will be more painful than a sharp incision of the same extent, but the hæmorrhage will be more easily controlled. A contusion or bruise is a subcutaneous laceration. It will occasion more or less extravasation of blood, known as ecchymosis. If the contusion is accompanied by a rupture of the integument, the discoloration will be less, as the effused blood and serum find an outlet. This constitutes a contused wound. It is usually made by some blunt instrument. The tissues may be crushed beyond recovery, in which case ulceration sets up around the dead parts, and they become gradually separated. Such separation is known as sloughing. All lacerations partake of the character

of contused wounds, as there is more or less bruising about the sides and edges. Gunshot wounds, being made by blunt bodies, are practically tubular contused wounds. They are very painful and likely to be accompanied by a deep-seated inflammation, as they usually contain foreign matter. Punctured wounds are those made by sharp-pointed instruments. If of any depth, they are dangerous, from the variety of tissues involved, and from the want of a free vent for any discharge that may be set up. Slight wounds may be rendered more serious by the introduction into them, either at or after the time of injury, of some poison or virus.

Burns are dangerous in proportion not so much to their depth as to the extent of surface involved. A burn covering half the surface of the body will result in death from shock; recovery is very rare if so much as one third of it is burned. Burns are sometimes classified as of three degrees: the first is a mere reddening, with slight swelling, owing to distention of the capillary blood-vessels. It is sometimes followed by desquamation of the cuticle. If the heat applied has been a little greater there will be a rapid flow of fluid out of the distended capillaries, and blisters will be formed containing serum, or serum mixed with blood. These may be raised immediately, or after a few hours. With a burn of the third degree the injury is still more severe, so as to destroy the vitality of the part. The gangrenous portion then gradually sloughs off, with free formation of pus, and the wound heals slowly by granulation. The cicatrix of a burn has a strong disposition to contract, and often produces great deformity. Severe burns are not infrequently complicated by inflammatory affections of the internal organs. The

lungs and kidneys often become deranged in their action, and gastric disorders are common. Perforating ulcer of the duodenum occurs seldom earlier than the tenth day after injury.

Scalds are, in effect, similar to burns, and frost-bites are analogous. Of the latter there are two degrees, one in which vitality is merely suspended, the parts being white, stiff, and numb, and developing an inflammatory tendency upon return of the circulation; and a second degree, in which the vitality is completely destroyed, and gangrene supervenes upon thawing.

There are five modes described, by either of which a wound of the soft tissues may heal. 1. By primary union, where two cleanly-cut surfaces, brought into close contact, simply grow together, without suppuration. This is also called healing by first intention. Wounds of the perinæum and of the face and throat are most likely to heal in this manner. 2. When union by first intention does not take place, there may still be primary adhesion. A layer of lymph exudes, gluing together the surfaces of the wound, which then unite promptly. 3. In the process of granulation, the wound is gradually filled up to the surrounding level by new tissues, appearing in the form of small red, close-set granules bathed in pus. 4. In secondary adhesion, two granulating surfaces, brought together, unite. 5. Under a scab, where the effusion of lymph forms a thick film, under which the healing process goes on, the surface of the sore contracting and acquiring a new skin. It takes a cicatrix a long time to acquire the vitality of the original structure; sometimes, indeed, it never does.

For ordinary purposes it is, perhaps, sufficient to classify wounds as healing by first intention, or by

granulation, without going further into detail. Destruction of the external tissues, attended by secretion of pus, is ulceration.

Granulations, if deficient, can be encouraged by stimulating applications, or be checked, if excessive, by astringents. Nitrate of silver is most often used for the latter purpose.

The healing of a granulating surface may be hastened by skin-grafting, which consists in placing upon it small portions of skin freshly cut from some part of the patient's or some other individual's body. If the operation is successful, each graft becomes a center around which cicatrization takes place, thus rapidly diminishing the size of the ulcer. The resulting cicatrix possesses more vitality, and is less liable to contract, than that which results from the ordinary healing process. In deep ulcers, prepared sponge is sometimes used for grafting. This is invaded by the granulations, and is subsequently absorbed. Antiseptic precautions must be taken in grafting.

The healing process is often hindered by inflammation, a series of changes in the blood and the tissues, resulting from irritation or specific poison, and manifested by heat, redness, swelling, pain, and suppuration. The swelling will be greatest and the pain least where there is the most loose tissue; in a bony or fibrous tissue, inflammatory pain is very severe. Inflammation attacking a mucous membrane is of less importance than when a serous membrane, or solid part, is affected, as the matter can find its way to the surface by one of the natural outlets; otherwise it is pent up in a cavity, or in the substance of some organ. An accumulation of pus in any of the tissues or organs of the body is an abscess. In opening an abscess the incision should