the vessel-walls into the tissues around, a process which need not here be described, as it is one with which you are no doubt already familiar. By and by the colored corpuscles, in groups of two to a dozen, also leave the central stream and pass through the walls of the vessels into the tissues, producing those patches of darker redness and the mottling of the surface alluded to above. The central stream next begins to oscillate, flowing onward during the systole, and slightly receding during the diastole of the heart; while the colored corpuscles show a tendency to adhere to one another. Finally the stream stops, and stasis is said to have occurred (Fig. 1).

In the meantime the liquid contents of the vessels have also been passing through the vessel-walls into the tissues, and this, together with the escaped leucocytes, accounts for the swelling and for the serous exudation which can be squeezed out when the parts are cut into. The serum, further, soaks into the neighboring healthy tissues, thus explaining the surrounding oedema, and is thence, along with some of the leucocytes, taken up by the lymphatics, and so passes back into the circulation, and as we shall presently see, may partly account for the attendant inflammatory fever. If now the cause of the inflammation ceases to act, and the vitality of the tissues has not been too much lowered to permit of their recovery, the corpuscles in the middle of the stream in those vessels where stasis has occurred again begin to oscillate and

then to move on; the leucocytes no longer drop out of the current, and those that have already escaped into the tissues either break down or pass along with the escaped fluids into the lymphatics, leaving

FIG. I.

Dilated vessels th

Dilated vessels,

increased flow.

with retarded

Leucocytes

Stasis with

ssue with

into

dense

connective Tissue.

ration o

imations

inflam

if at the

flow and escape of

connect

the part apparently un- Diagram of the minute changes in inflammation. injured.

If the above favorable termination does not take place and stasis is not soon relieved, coagulation of the serum rapidly ensues, and the vessels become thrombosed. At the same time,

moreover, coagulation of the liquid exudation in the tissues also occurs, in consequence, it is said, of the fibrin ferment contained in the leucocytes causing the fibrinogen in the liquid to unite with the fibrino-plastin in the leucocytes. The clot thus formed contracts, squeezing out the serum, which is then drained away by the lymphatics, so that if the parts at this stage be cut into, a serous exudation will no longer escape. The original tissues of the part, partly in consequence of the primary injury, partly in consequence of the accumulation of leucocytes and fluid exudation, and partly in consequence of the plugging of the vessels, completely lose their vitality and become swollen and softened, and finally disappear among the leucocytes, which then completely take their place, forming a mass of closely packed small cells embedded in a very slight amount of intercellular substance. Under favorable circumstances capillary loops, derived from the vessels around, grow among these cells, which now go by the name of granulation tissue; and the cells themselves become gradually converted into fibrous tissue, producing the condition already referred to of fibroid thickening or scarring. Under less favorable circumstances the intercellular substance in the centre of the mass of closely packed cells liquefies; and the cells, cut off from their nutrient supply, undergo degeneration and die, and are then known as pus-cells, while the liquefied tissues and exuded serum form a liquid (liquor puris) in which they are contained. Thus pus is formed, and suppuration is said to be established. When this degeneration occurs on the surface of the skin or mucous membrane, and the products can escape externally, the process, though essentially similar to that of suppuration, is spoken of as ulceration. And lastly, the infiltrated tissues in the centre of the inflamed area may lose their vitality and die en masse, before infiltration with leucocytes has gone on sufficiently to produce their softening; and mortification or gangrene is then said to result.

Theory of the Inflammatory Process.-The theory most generally held at the present day is that the inflammatory process is one of lowered vitality and not, as was formerly taught, of increased nutritive activity; that the irritant or exciting cause acts by producing some molecular change in the vessel-walls, thereby rendering them capable of behaving toward the blood more or less like dead matter, and thus promoting a tendency to stasis and coagulation and the escape of leucocytes and serum in abnormal quantities; that the inflammatory small-cell exudation, formerly regarded as a proliferation of the tissue elements, is derived from the accumulation of the escaped leucocytes in the tissues; and that the tissue elements themselves remain passive or undergo degeneration.

Causes of Inflammation.-The molecular change in the vesselwalls, which it is probable is the direct cause of the inflammatory phenomena, may be brought about by some influence acting upon them, I, from within, through the blood; and 2, from without, either directly upon the vessel-walls themselves, or indirectly through the intervention of the contiguous tissues. Irritants acting in either of these ways may be looked upon as exciting causes, and would appear in some instances to be alone sufficient to set up the process. In other cases, however, certain prior conditions such as may be considered to lower the vitality of the tissues, and to render them less able to resist deleterious influences, appear necessary to render such irritants operative. Among such predisposing causes may be mentioned: 1. A deficient supply of healthy blood induced by insufficient or improper food, a feeble action of the heart, hemorrhage, anæmia, and the like. 2. The presence of impurities or of certain poisons in the blood, such as exist in chronic alcoholism, Bright's disease, diabetes, gout, syphilis, and in lead, mercurial and phosphorous poisoning. 3. Deprivation of healthy nerve influence, as from disease or injury of a nerve centre, or nerve trunk. 4. Old age. 5. The strumous diathesis.

The exciting causes, which are usually spoken of as irritants, may be considered under the following heads: 1. Direct violence. 2. The chemical products of putrefaction. 3. Infective micro-organisms.

1. Direct Violence.-Under this head are included all forms of mechanical injury, excessive heat or cold, electrical stimulation, the application of strong acids or alkalies, or irritating products, as croton oil or mustard, friction, and tension.

The above are regarded, as here, by the majority of surgeons as exciting causes. By the extreme supporters of the germ theory, however, they are merely considered as predisposing causes, the exciting cause, according to these pathologists, being in every case micro-organisms. The character of this work will not permit of the discussion of the arguments for and against such a view, and it must here suffice to say that Dr. Burdon Sanderson, the highest authority on the subject in this country, has no doubt that inflammation can be induced by mechanical or other violence without the intervention of micro-organisms, although he admits that injuries which are in themselves inadequate to produce inflammation acquire that power when microorganisms are present in the circulation.

2. The Chemical Products of Putrefaction would appear to play an important part in the causation of inflammation, and are probably the chief agents at work in the production of spreading

suppurative inflammation when it occurs in wounds. For putrefaction (or sepsis as it is often called) to occur, there must be dead animal matter, a sufficiency of water and oxygen, the main. tenance of a certain temperature, and the presence of a ferment. This ferment, according to the germ theorists, consists of living microscopic organisms, called bacteria, which are said to exist in large numbers in the air, water, etc., in fact everywhere, except in mid-ocean and above the snow line on mountains, and to be especially numerous in large cities, hospitals, etc. They are no doubt invariably present where putrefaction is going on, but whether they are the cause, or merely the result of the putrefactive process as the opponents of the germ theory maintain, is still open to question. Be this as it may, it is not thought that the inflammation is lighted up by the bacteria themselves, but by the chemical products (ptomaines), which are formed in the process of putrefaction, and which soak into the surrounding tissues, acting like any irritant fluid. For it has been found that when fluid swarming with bacteria is injected into the blood or connective tissue of a living animal, the bacteria rapidly disappear without causing inflammation or other ill effect. Again, if a similar fluid is injected into the peritoneal cavity in such quantities only as to allow of its rapid absorption, no inflammation ensues. On the other hand, if such fluid, or even pure water, is injected in quantities more than can be rapidly absorbed, serum from the blood is effused into it; and as all the essentials for putrefaction are now present, viz., diluted serum which constitutes the dead animal matter, heat, moisture, oxygen, and ferment, putrefaction ensues, and inflammation results. From these and similar experiments it is inferred that the bacteria themselves are incapable of setting up inflammation; that they are only able to thrive in dead animal matter, and not in living tissues; and that it is the products of putrefaction, of which they are probably the cause, that set up the inflammatory process.

3. Infective Micro-organisms.-These, which include the various species of micro-organisms, known as the bacillus and micrococcus, are also believed to play an important rôle in the causation of inflammation. Indeed, they are believed by some pathologists to be the essential factors in all inflammatory processes. But while it cannot be admitted that they are the exciting cause of all inflammation, the belief is fast gaining ground that they are important, if not the chief agents in many inflammations, and especially in those inflammations which, because they occur without any apparent cause, were formerly spoken of as idiopathic. Thus erysipelas and some forms of periostitis appear prob

ably to depend upon them, while malignant pustule has been proved to do so. Unlike bacteria, the organisms which are found in all decomposing fluids, and which as we have seen are unable to exist in the living tissues, many species of bacilli and micrococci are not only capable of living in such, but thrive and multiply in them, and while doing so give rise to certain irritating products which set up inflammation. Hence they are called infective, parasitic, or pathogenic fungi. They are supposed not only to multiply and spread in the surrounding tissues, setting up inflammation in their course, but also to enter the system by the blood and lymph vessels, where, still multiplying, they poison the body generally; and in consequence of their becoming lodged in various tissues or organs of the body, where they further multiply and thrive, to set up a like inflammation. The way in which they enter the body is either by a wound direct, or else by the alimentary or respiratory mucous tracts. Where they enter by a wound, it appears that decomposition of the discharge favors their entrance (as in erysipelas occurring in a septic wound), though such is not essential. They or their spores are supposed to exist in the air, water, etc., but in less quantities than the bacteria, and only occasionally, as when a case of specific inflammation to which they are supposed to give rise is present in the same ward.

As bacteria, bacilli, and micrococci will have to be frequently mentioned, they may be here briefly described. The common form of bacterium (bacterium termo) is a rod-like body about 25000 of an inch in breadth, and less than twice its breadth in length. It multiplies by fissure, not by spores. It is easily killed by antiseptics, and will not thrive in living tissues; hence it is named nonpathogenic, and, as it is always found in putrefying or septic fluids, it is also spoken of as the carrion or septic fungus.

sure.

The bacillus is also a rod-like body, but it is more than twice its breadth in length. It multiplies by spores as well as by fisIts spores resist heat and cold, chemical reagents, drying and strong solutions of carbolic acid, but are killed by bichloride of mercury and permanganate of potash. The bacilli of surgical interest are the anthrax bacillus, the cause of malignant pustule, the tubercle bacillus found in tubercular disease, and the bacillus of glanders, of leprosy, of syphilis, and of tetanus.

The micrococcus is a round or oval body, from 0 to 75000 of an inch in diameter. It occurs singly or in pairs, sometimes in chains or in colonies known as zoöglœa masses, and multiples probably by cell division. Micrococci, though often found in putrefying fluids, are, like the bacilli, not thought