Various forms of sterilizers are so cheap that in hospital practice a separate sterilizer may be used for each set of dressings. From eight to twenty layers of gauze should cover the wound and the surface for some considerable distance beyond the limits of the wound. A layer of moist iodoform gauze or sterilized gauze dipped in sublimate solution should be placed immediately over the line of union, as slight moisture increases the capillary absorbing power of the dressing. The gauze is covered over with several layers of absorbent cotton, and all are securely held in place by a roller bandage, preferably of gauze also. It is sometimes wise to change the dressing of a large wound attended with much oozing at the end of twenty-four hours, when the drainage-tubes, if used, may be removed. The change of dressing should be done with all the antiseptic precautions employed at an operation. If the fluids do not. soak through the dressing, no change should be required for several days. It is well to keep a dressed wounded part exposed to a free circulation of air. In the case of a wound about the pelvis this may be accomplished by the use of a cradle. The air beneath the bed-clothes is apt to become foul.

3. Moist Dressing. In the case of septic wounds, where rapid absorption of the discharges and disinfection of the wound-surfaces are desirable, healing may be promoted by substituting a wet antiseptic dressing for the usual dry one. This form of dressing may also be advantageously employed in the treatment of contused and lacerated wounds where the facilities may not be at hand for an antiseptic operation and dry dressing. The wound is dusted over with iodoform or aristol, and then covered with a large compress of sterilized gauze moistened in a 1:1000 corrosive-sublimate or 1:60 carbolic solution; creolin, 1 per cent.; or aluminum acetate, saturated solution, may also be used. A piece of impermeable material, such as "gutta-percha tissue," should widely cover the whole dressing, and all is held in place by a loosely-applied roller bandage. It may be desirable to remoisten the dressing every hour or so with a few drachms of the same solution as used.

What is the roller bandage?

Roller bandages are made from plain, sterilized or corrosive-sublimate gauze, and are used for retaining dressings in position, making equable pressure, and restraining motion. The material from which the bandage is made is cut in strips three to ten yards in length and from one-half to four inches in width. It should be applied

evenly and smoothly to the surface by circular and spiral turns, so as to retain its place during the ordinary movements of the patient. Where a firm support is required muslin, canton Alannel, or flannel should be the material selected. For producing absorption in the treatment of certain joint diseases by elastic pressure, a roller of pure rubber is used.

Define the process of repair.

This is the process by which tissues which are the seats of wounds or contusions are restored approximately to their former condition. The term "approximately" is used for the reason that the process of repair always results in the formation of an amount of connective tissue in excess of that which was originally in the wounded or contused parts. This excessive connective tissue, when the process is complete, is the cicatrix or scar.

Describe the process of repair.

Absorption of the effused blood and of the destroyed tissueelements; exudation of lymph, serum, and fibrin: this last forms a sort of framework, so to speak, into which pass white blood-corpuscles, which soon become changed into regular connective-tissue cells. Other new connective-tissue cells are also formed in this "framework" by proliferation from the cells in the surrounding tissues. At the same time new blood-vessels are formed, as well as fibres and intercellular substance. Additional factors in the production of new connective-tissue cells are the fibroblasts, or certain cells found in the walls of the new arteries. But the process is not yet complete. What is formed is not adult connective tissue, but resembles embryonal connective tissue. It is always spoken of in connection with repair as granulation tissue (see below). The final stage consists simply in the maturation of this tissue until it becomes fully developed and of the "adult" type. The above phenomena greatly resemble the changes caused by a mild degree of inflammation, but they occur without bacteria or septic infection, hence are not 66 inflammatory."

Discuss the process of repair as it occurs in the different wounds.

In incised wounds whose edges have been approximated, the process of repair goes on as already described, except that as there is no loss of substance to be made up, but only union to be effected between two raw opposed surfaces, it is necessarily of very limited extent. In fact, it results in the formation simply of a very thin

layer, first of granulation tissue, and then of cicatricial tissue, between the two edges, for the entire depth, of the wound. When wounds are closed in this manner they are said to heal by primary union or first intention.

In lacerated wounds there is actual loss of substance to be made up; hence the process is extensive, and results in a mass of granulation tissue filling in the gap or cavity existing between the edges, which are more or less widely separated. This granulation tissue in lacerated wounds can be seen, and its surface is found to be not smooth, but covered with numberless little points resembling granules or granulations, whence its name. Furthermore, there is always an excess of white corpuscles in this process of repair in lacerated wounds, which appears on the surface of the granulations as pus. If the wound is being repaired or healing aseptically, this "pus would scarcely be evident at all, and the discharge would apparently consist only of serum. But, owing to the difficulty of keeping such wounds aseptic, there is almost always an entrance of pyogenic bacteria, and hence an amount of suppurative inflammation, however slight it may be, is present, sufficient to produce the purulent discharge usually seen on the surface of wounds healing in this way. The wound is now an ulcer, and the last stage of repair consists in the advancement of epithelium from the surrounding skin over the surface of the granulations. Wounds closing in this manner are said to heal by granulation, or second intention. Punctured wounds also heal by "granulation."

What is healing by secondary union?

This is simply union effected by bringing together the edges of a wound whose surfaces are already covered with granulation tissue.

What is healing "under a scab"?

A wound starts in to heal by granulation in the usual way, but very soon there is formed on the surface a covering of coagulated blood, dried discharge, etc., which is called a scab. This scab stretches a little way beyond the edges of the wound, and under it the process of healing by granulation goes on to completion, including also the advancement of the epithelium.

Contusions are healed by granulation, the process being all the while, of course, covered in by unbroken skin.

Describe the process of repair in fractures.

It is exactly the same as already described, except, of course, the addition of lime-salts to what is first granulation tissue and later bony-cicatricial tissue, which bears the same relation to normal bone tissue as ordinary cicatricial tissue does to pormal connective tissue. This bony-cicatricial tissue is called callus, and it forms in three places: (1) as a plug between the ends of the bones, extending from one medullary canal into the other; (2) between the opposed surfaces of the compact tissue; (3) beneath the periosteum on and along the superficial surface of the line of fracture. All this is temporary callus, and it becomes sufficiently hard to permit use of the limb in from six to eight weeks. The permanent callus is the permanent bony cicatrix into which the temporary callus in situations 2 and 3 (see above) becomes converted. This transformation takes from three to four months, during which time also the medullary plug of temporary callus is absorbed by physiological rarefying osteomyelitis (see Inflammations of Bone), and the continuity of the medullary canal is restored.

What is the process of repair in nerves?

If a nerve is divided, it may be possible to secure union at once between the divided ends. As a rule, however, the nervous elements of the entire distal section degenerate, and regeneration is effected by proliferation of nervous elements from the proximal section.

INFLAMMATION.

CLASSIFICATION AND VARIETIES.

What is inflammation?

Inflammation is an alteration in the structure of tissue accompanied by certain symptoms. This may be explained as follows: Any given area of tissue is made up of (1) tissue-structure proper, and (2) blood- and lymphatic vessels, which, for brevity, will be called the vascular supply. In health these two elements have a relationship to each other which is called normal, and which is based on the amount and the condition of each element present. This normal relationship varies, of course, in the different tissues. Hence anything which effects a variation in this normal relationship causes a change in tissue-structure, and this change, if accompanied by

certain symptoms, is called inflammation. On the other hand, if such a change is brought about by traumatism, it is called a contusion or a wound, each presenting its characteristic symptoms.

What are the different kinds of inflammation?

The change in tissue-structure already referred to may take place in one of two ways-viz. (1) by an alteration of the tissue-structure proper; (2) by an alteration of the vascular supply. In either case the amount or quantity and the condition or quality of each may be affected. Thus we may have a change in the amount of tissue proper-i. e. it may be increased or diminished; or its quality may be changed-i. e. a different kind of tissue may be substituted for the original tissue. Or the vascular supply may be increased or diminished by dilatation or contraction of the vessels, or the quality of the vessel-walls may be so altered that exudation of lymph or of one or other or of all the constituents of the blood is allowed. Therefore it follows that each of these changes corresponds to and is identical with a certain kind of inflammation.

These various inflammations are classified as follows: Inflammations of the tissue-structure proper are called non-exudative inflammations; those whose presence is shown by exudation of the blood-elements or of lymph are known as exudative inflammations; while to those which are characterized by increased or diminished vascular supply are given the names hyperemia and anæmia respectively. It is understood of course that any one of these inflammations may occur either singly or associated with one or more varieties.

Explain more fully the non-exudative inflammations.

As already stated, these inflammations are changes in the tissuestructure proper. They are subdivided as follows: If the tissue is simply increased in amount, and at the same time retains its original characteristics, the inflammation is called non-specific productive inflammation. If, on the other hand, there has taken place a change in the quality of the original tissue, and a different kind of tissue of a certain definite structure has been substituted, the inflammation is called a specific productive inflammation. The terms "specific" and "non-specific" will be explained later on.

There remains that form of inflammation in which the tissuestructure is diminished or destroyed. This is called inflammation with the destruction of tissue, or "destructive" inflammation.