Definition. Inflammation may be defined as the local reaction against injurious influences. An aseptic wound heals without any of the clinical signs of inflammation and without reaction. It is only by a study of the minute changes about such a wound that the resemblance, between the processes of wound repair and those of slight inflammation, become evident.

Etiology. The cause of inflammation is any injury to the tissues by mechanical, thermal, or chemical means; by the effect of electricity, or by the growth of bacteria.

Pathology. Inflammation occurs through changes in the circulation.

When one of the causes mentioned above acts upon the tissues, the first alteration seen is an increasing blood supply to the part, the arterial circulation being increased both by the greater rapidity and force of the current through the vessels, and by the dilatation of all the small branches and capillaries.

When the inflammation grows more intense, the circulation in the capillaries becomes slower and the corpuscles collect, until they clog the vessels. The normal current of blood in small vessels, as seen under the microscope, shows a thick central stream of corpuscles with a transparent border of lymph (containing only a few white corpuscles) between it and the vessel wall.

As the stream diminishes in rapidity, the number of white cells in the clear space increases, the blood plaques appear also, and finally, when the current is reduced to stagnation, the clear space disappears, being filled entirely with cells, chiefly leucocytes, although red cells find their way into it.

This tendency of the white cells to separate from the others, even when the current is rapid, is partly due to their viscosity and power of ameboid movement, but in the main is a purely mechanical effect of the slower current.

It has been proven that when particles of different density are suspended in a liquid which is circulating through a system of narrow tubes with a very rapid current, there is a clear space next to the wall of the tube where the friction necessarily reduces the speed of the fluid which is free from particles, and, as the current is slowed down, some of the particles of least density, begin to appear in this clear space, their number increasing as the current becomes slower, until even the heavy particles also collect here when it is very slow.

It is known that among the cellular elements of the blood, the leucocytes have the least specific gravity or density, and the blood plaques rank next, while the red blood disks are the heaviest, and these bodies appear in the clear serum near the vessel wall in that order, according to the law just cited. The slow current is associated with an increased intravascular blood pressure, which, in part, is the cause of the phenomena of exudation, emigration and diapedesis.

Exudation. Serum of the blood passes out of the vessels, and collects in the lymphatic spaces in the cellular tissue, and elsewhere, and also exudes from the surface of the mucous membranes or forms vesicles or blisters in the skin by detaching the superficial epithelial layers. Complete stasis, or stoppage of the circulation is seen only when the inflammation is exceedingly intense, and would cause the death of the part if continued long.

Usually the current merely becomes slower than normal. This retarded circulation is followed by the phenomena of emigration.

Emigration. Emigration of the white blood corpuscles consists in the passage of the cells directly through the vessel walls. It is most frequently seen in the capillaries, although it also takes place in the small veins. The white corpuscles, or leucocytes, have the property of ameboid movement, stretching out at will in any direction, long, narrow processes of their protoplasm, called pseudopodia, which may be attached to any object, and having secured such an anchorage, the rest of the protoplasmic body is drawn towards it.

In this way, the leucocytes are able to pass through the interstices between cells, or along narrow channels in the tissues. When the blood current becomes sufficiently slow to enable them to cling to the walls of the vessels, it is then that ameboid movement begins. Sometimes the cells loose their hold and are swept on again, but in other cases a minute bud of protoplasm will appear on the other side of the wall of the vessel, opposite to the spot where the leucocyte is clinging, and as this grows larger, a narrow neck of protoplasm can be traced through the wall directly to the leucocyte, and presently the mass of the leucocyte becomes proportionately smaller as the external bud of protoplasm grows larger. The conditions are gradually reversed, the nuclei of the cells appear outside and only a small mass of protoplasm remains within the vessel until finally the entire leucocyte is in the tissue outside of the vessel and is free to wander in any direction.

The mechanical part of this process is not yet understood. It is claimed by some that small openings exist in the walls of the vessels, between the endothelial cells which line them, to which is given the name of stomata. These openings ordinarily are invisible, but they are said to enlarge under the effect of the dilation of the vessels, and of the alterations in their walls, produced by the inflammatory reaction, and that the leucocytes escape through those openings.

There can be no doubt that the emigration is due to the ameboid motion of the cell, and the discovery of the phenomenon, to which is given the name chemotaxis, affords a sufficient explanation.

This is the influence possessed by certain substances to attract or repulse ameboid cells. In some cases this attraction appears purely to be mechanical, but it is probably a chemical effect of some kind in most, if not in all, instances.

The process of inflammation produces some chemical compound which similarly causes the cells to leave the vessels, and when there is any inflammatory action in their neighborhood, to find their way by the shortest route to the seat of the inflammation.

The leucocytes direct their course through the tissues to the chief points of inflammation by reason of chemotaxis, and surround the dead tissues, or any point of bacterial growth, or any foreign body which may be the cause.

The wandering leucocytes form the pus cells, and if they are very numerous, they constitute a purulent or suppurative inflammation. The wandering cells, however, are almost entirely made up of leucocytes, of which three forms are known, varying in size and in the size and number of their nuclei. The leucocytes surround any foreign body, and if the particles are small enough, they incorporate them within themselves, in fact, they may be said to swallow them. This taking up of particles by the wandering cells is called phagocytosis.

Diapedesis. When the circulation becomes very low and the pressure very high, there is a tendency of the red corpuscles to leave the vessel.

This is a purely passive process, and is observed only when the changes in the vessel wall are extreme. Both varieties of these cells die and are destroyed in the exudate, the former furnishing the fibrin which is so abundant in some forms of inflammation. This escape of red corpuscles is known as diapedesis, and is sometimes so extensive as to amount to capillary hemorrhage.

Symptoms. From antiquity the local symptoms of inflammations have been enumerated, as heat, redness, pain and swelling and to these has been added, impaired function.

The redness is due to congestion. The pain is due to the pressure exerted on the sensory nerves by the surrounding swelling, as is well shown by the intensification of the distress, as every beat of the heart forces more blood into the space already filled. In some cases, however, it may be caused by the direct action of the inflammatory agent upon the nerves. The heat is caused by the increased supply of warm arterial blood, for it has been abundantly proven that the temperature never rises above the heat of the blood, although naturally in a patient with fever, it will be above the normal temperature of that fluid. The swelling is due to the dilated vessels, and to the escape of serum and blood cells from the vessels into the tissues. The impaired function is chiefly caused by the pain which is often increased by any attempt to use the part, and by the swelling which prevents free movement, though the loss of function may also be dependent upon the direct action of inflammation upon the nerves.

The constitutional symptoms of inflammation are an elevation of temperature with or without a chill. There are also other disturbances, such as nausea, vomiting, diarrhea, sweating and polyuria. These are due to efforts on the part of the general economy to eliminate toxic substances.

The inflammatory products may poison the system in two ways: (1) by the diffusion of their chemical substances, (toxins and ptomains), or (2) by the passage of bacteria themselves into the blood.

Termination. Inflammation may result in resolution, suppuration, necrosis or sloughing, or in the establishment of a chronic state.

Resolution. Resolution is the termination of an inflammation by the gradual cessation of all the changes which have occurred. The pain subsides, the circulation becomes more normal, and the exudate is absorbed, or makes its way to the free surface of the body, where drainage occurs either spontaneously or by incision.

If there has been any loss of substance caused by the inflammation, it is restored by processes exactly similar in character to those in the repair of wounds.

Suppuration. Pus consists of a serum containing little or no fibrin and large numbers of leucocytes. There are also many cells, either dead or dying, which represent the waste thrown off from the tissues as a result of the inflammatory reaction. A purulent inflammation or suppurative inflammation, is one in which there is pus formation.

When suppuration occurs, the pus may make its way to a free surface, such as a mucous membrane, or may form an abscess, or may cause sloughing of the skin over the seat of inflammation, and so escape from the cellular spaces in the tissues.

Pus may be thrown off by a mucous membrane, without any actual breach of continuity. Diffuse infiltration of the tissues is the most dangerous form of suppuration.

In this variety of inflammation the exudate is brought into contact with the greatest possible extent of absorbent vessels, for as a surface of a sponge is greater than that of a bag, which would contain it, so the surface of these intercellular spaces is much greater than that of an abscess cavity filled by the same amount of pus. In this form the bands of cellular tissue, lying between and forming the boundaries of these spaces, remain intact, and the exudate is either absorbed into the circulation, or seeks escape through many punctate openings in the skin.

The entire skin of the part is frequently detached from the fascia by the sloughing of the subcutaneous tissues, before it gives way, and even when it finally yields to the necrotic process, the openings formed will be altogether too small in proportion to the extent of the disease beneath, so that healing is still further delayed.

Sloughing. Inflammation may be accompanied by sloughing or death of tissues. Gangrene, mortification or necrosis is a death of the tissue from any cause. The part which has died is designated as a slough.

When inflammation has subsided, granulation tissue forms on the living tissue, exerting pressure upon the slough, thus hastening its absorption or separation.

Chronic Inflammation. An interruption at some stage of resolution or suppuration and the continuance of mild symptoms constitutes a chronic state.

By chronic inflammation, we understand a long continuance of some or all of the changes seen in acute inflammation, but less in intensity, and an abnormal tendency to the production of new tissue.

Treatment. The general indications to be observed in the treatment of inflammation are: (1) to combat the congestion of the parts; (2) to relieve tension; (3) to give free issue to the products of inflammation; (4) to produce early separation of sloughs.

Very hot or very cold applications exert a beneficial and soothing effect upon inflamed areas.

Cold has the tendency to reduce tension by constricting the blood vessels thus diminishing the amount of blood supplied. In an infected area the reproduction and development of bacteria are checked, and suppuration is frequently aborted.

Heat has the effect of dilating the blood vessels and hastens repair in bruised, strained, or torn tissues. This is a variety of hyperemia treatment which is especially useful in the absence of bacteria. In infected areas the growth of bacteria, and increased pus formation, would be encouraged and heat is contraindicated.

We are yet without an antiseptic material which can be used in sufficient strength to affect the growth of germs and yet not injure the patient. Injury of the part treated, and absorption into the circulation are both to be avoided. The application of dressings, wet with corrosive sublimate, or other chemical solutions to the unbroken skin over inflamed areas, is a fallacy. Any benefit which has been observed to follow their use, has undoubtedly been due to the effect of the moisture and warmth or cold, according to the temperature of the dressing, thus obtained, while local sloughing and general constitutional poisoning are a common result of such applications. A light gauze dressing, applied cold, and kept constantly wet with any evaporating solution, will greatly relieve the congestion and so assist the inflamed tissues in their contest with any irritating materials.

A thick wet dressing made with a hot solution, and well protected against evaporation so that it will retain its heat, will produce the same effect as a poultice, although less powerful. When there are discharging wounds or raw surfaces, unprotected wet gauze should be employed, for poultices are then inadmissible, and the weak antiseptic solution will inactivate and wash away bacteria.

Astringent solutions have an excellent effect upon inflammatory processes and the most generally useful of these is the 50 per cent. solution of acetate of aluminium.

The following is a modified Burow’s solution:

Filter after mixture has been allowed to stand for 24 hours.

Ointments are employed by many in the treatment of small areas of inflammation; they are useful, though not as efficient as hot or cold wet dressings. Over the unbroken skin, they can only act like a poultice and should not be employed where infection exists. On clean wounds they are unnecessary, but upon ulcers or wounds which show no tendency to heal, such ointments as Peruvian balsam, 5 per cent., or scarlet red, 4 per cent., are extremely valuable.

THE PROCESS OF REPAIR

Regeneration of Tissues. The reparative powers of the tissues of the human body are considerable, although not comparable with those of the lower animals, in the lowest orders of which the reproduction of an entire limb, or even one-half of the body, may take place. In order to understand the regeneration of tissue, we must first consider briefly the life history of the cells.

A cell consists of a mass of protoplasm, generally enclosed in a cell membrane, and containing a nucleus and nucleolus. The nucleus represents the most vital part of the cell protoplasm, and has a more granular appearance than the latter. The nucleolus is a minute solid spot in a nucleus, appearing to be more highly refractive.

Cell Division. When the cell is quiescent, the protoplasm appears evenly granular, but when it is stirred to active life, slender twining threads can be traced in the nucleus, perhaps consisting of one long thread twisted upon itself.

On account of their readiness to take up dyes used in staining, these threads are called chromatine threads.

When the cells are about to divide, the chromatine threads are seen to arrange themselves in a line across the center, called the equator of the nucleus, forming a rosette or star shape, known as the mother star. Some large granules then appear in the nucleus at points on either side of this line, which are known as the poles of the nucleus. The loops of the thread are directed towards the poles. Gradually these threads become arranged in radiating lines, converging at the poles, and then break away from their former connections with the equator, forming a daughter star at each pole, a clear space appearing at the equator. A constriction next appears in the now clear equator, and the nucleus divides into two distinct nuclei. Simultaneously with this division, or immediately following it, the protoplasm of the cell body divides in the same place, and thus two complete cells are produced. The chromatine threads lose their rosette arrangement, and gradually become imperceptible as the new cell returns to the quiescent state. This process of cell division is known as karyokinesis or aryomitosis.

In simple cells like the leucocytes, reproduction may take place by simple fission, thus: a constriction appears in the nucleus and in the body of the cell in the same line, and the two divide without any visible protoplasmic changes. Such a simple mode of division does not occur in the more highly specialized cells of various tissues. If the karyokinetic action be not very vigorous, the nucleus may divide, but the cell body remains intact, producing the cell with two or more nuclei so commonly observed. Every cell reproduces its kind, spindle cells producing connective tissue; epithelial cells epithelium; and bone cells producing bone.

Repair of Wounds and Healing by Apposition. When a wound occurs, the cut edges immediately retract on account of the elasticity of the tissues, and the gap fills with blood and serum. If no bacterial or chemical irritant is introduced, there are no true inflammatory changes. The divided blood vessels are soon plugged with coagulated blood, which extends into the cut vessels to the nearest branch. The capillaries around the seat of injury dilate slightly, the fixed cells of the tissues become active, dividing by karyokinesis as already described. The endothelial cells lining the divided blood vessels multiply and take an active part in the process. In spite of the congestion and the new cells produced, the reaction is much less than that of inflammation. The new cells invade the blood clot, consuming it and also any foreign matter, or any tissue which may have been killed by the injury. From the loops of the occluded capillaries, at the sides of the wound, spring buds of endothelial cells, becoming thicker and then hollow as they extend, blood cells forming in them and blood entering them also from behind. These advancing endothelial tubes join with those on the opposite side of the wound, and thus the new forming tissues are supplied with blood vessels.

It is said that new vessels are also formed by the pre-existing lymph-spaces and by independent cells. Meantime the connective tissue cells have been forming fibres across the clot and epithelial cells over its surface, if skin or mucous membrane be involved in the injury. The new vessels disappear, and the new connective tissue forms the scar. This is the process of primary union in a wound in which there is not a marked cavity or a loss of tissue on any of the exposed surfaces of the body, and no matter how closely the edges of such a wound may lie in contact, it can heal by no other method. Even the closest apposition of the sides of a wound cannot prevent the interposition of a thin layer of clot and the partial death and absorption of a very thin layer on its surfaces. This is also known as primary union.

Healing by Granulation. When a wide gap has been produced by retraction or by actual loss of tissue, healing takes place by granulation, as it is called, a process which differs from that just described merely in the fact that more tissue must be reproduced. The outpouring of blood and serum, occlusion of the vessels, congestion, multiplication of fixed cells, emigration of leucocytes, and production of vascular loops and buds, goes on as before. As the formative changes advance, small, round elevations of a rosy color appear on the new surface, making it look like velvet. These rounded elevations of the healing surface are called granulations.

They advance steadily on all sides, filling the gaping wound until the level of the original surface is reached, the new tissue organizing behind them, and contracting as it organizes, so that the space to be filled is daily made smaller by this contraction as well as by the production of new tissue. As the surface is reached, the epithelial cells on the edges of the granulating area slowly spread over it, the granulations generally projecting above the adjoining surface and the epithelium growing over them as they contract again to their proper level. The advancing line of epidermis is visible as a pink line, gradually whitening with time.