There is much foundation for believing that healthy inflammation is invariably a homogeneous process, obedient to ordinary principles, and that in similar structures, situations, and constitutions it uniformly assumes the same features. If experience reveals to us that here it is commonly productive of certain effects, and there of different ones, the same unbounded source of wisdom communicates to the mind a knowledge that there is some difference in the tone of the constitution, or in the structure or situation of the parts affected, assignable as the cause of this variety.

Some authors make the nature of the exciting cause one principal ground of the specific distinctions in inflammation; and with good reason, for they take into account the action of morbid poisons, and the qualities of disease in general.

In burns, for example, the inflammation is unquestionably attended with great peculiarity, requiring different treatment from that of common inflammation in general. But when the exciting cause is strictly mechanical, its violence and extent may cause differences in the degree and quantity of inflammation; but with respect to its quality, this must be accounted for by constitution or other circumstances.

It was Dr. Hunter's doctrine that parts which, from their vicinity to the source of the circulation, enjoy a vigorous circulation of blood through them, undergo inflammation more favourably, and resist disease better, than other parts of similar structure more remote from the heart. The lower extremities are more liable to inflammation than parts about the chest. When inflamed they are longer in getting well, and the circumstances of their being depending parts, which retards the return of blood through the veins, must also increase their backwardness in any salutary process.

Common inflammation, when situated in highly organised and vascular parts, is generally more disposed to take a prosperous course, and is more governable by art than in parts of an opposite texture. Hence common inflammation of the skin, cellular tissue, muscles, etc, more frequently ends favourably than the same affection of bones, tendons, ligaments, &c; but inflammation of vital parts, though they may be exceedingly vascular, is less likely to go on favourably than in other parts of resembling structure but of different functions, because the natural operations of universal health depend so much upon the sound condition of such organs.

Again, all new-formed parts, not constituting any portion of the original structure of the body, such as tumours, both of the encysted and sarcomatous kind, excrescences, etc, cannot endure the disturbance of inflammation long, nor in great degree. The vital powers of such parts are weak, and when irritated by the presence of inflammation, these adventitious substances are sometimes removed by the lymphatics, but more commonly mortify. This remark applies also to substances generated as substitutes for the original matter of the body; for instance, the substance of a cicatrix, or of callus. Now, the knowledge of this fact leads us to a rational principle of cure in the treatment of several diseases. It is, again, worthy of notice that inflammation always proceeds more favourably in strong than in weak constitutions; for where there is much strength there is little irritability. In weak constitutions the operations of inflammation are backward, notwithstanding the part in which it is situated, and may, comparatively speaking, possess considerable organisation and powers of life.

Healthy inflammation, wherever situated, is disposed to be most violent on that side of the point of inflammation which is next to the external surface of the body. Take an illustration which will more explicitly express my meaning: When inflammation attacks the socket of a tooth, it prevails in the greatest degree, not at the inner side of the alveolary process, but towards the cheek.

"We may observe the influence of this law in several diseases, but more particularly in gunshot wounds. Suppose a ball were to pass into the thigh, to within an inch of the opposite side of the limb, we should not find that inflammation would be excited along the track of the ball, but on the side next to the skin which had not been hurt; or, if a ball were to pass quite through a limb, and carry into the wound a piece of cloth, which lodged in the middle, equidistant from the two orifices, the skin immediately over the extraneous or foreign body would inflame, providing the passage of the ball was superficial.

"We now notice three remarkable effects often following common inflammation; namely, adhesions of parts of the body to each other, the formation of pus, or suppuration, and ulceration, a process in which the lymphatics are sometimes thought to be more or less actively concerned than the bloodvessels. Hence Dr. Hunter termed the different stages of inflammation the adhesive, the suppurative, and the ulcerative. But all parts of the body are not equally liable to each of these consequences.

In the cellular textures, and in the circumscribed cavities, or those lined by a serous membrane, the adhesive stage takes place more readily than the others; suppuration may be said to follow next in order of frequency, and, lastly, ulceration. This statement must be received, however, with the understanding that the inflammation is healthy, and not excessive; for, when it is erysipelatous, carbuncular, or influenced by unfavourable conditions of the general health, or marked by violence of degree, no texture suffers injury and even destruction so frequently, or to so great an extent, as the cellular tissue; and where it does not actually mortify under these circumstances, it becomes a frequent

In internal canals, on the inner surface of the eyelids, nose, mouth, and trachea, in the air-cells of the lungs, in the cesophagus or gullet, stomach, intestines, pelvis of the kidney, ureters, bladder, urethra, and in all the ducts and outlets of the organs of secretion, being what are termed mucous membranes, the suppurative inflammation comes on more readily than either the adhesive or the ulcerative.

Adhesions which originate from the slightest degree of inflammation in other situations and structures, can only be produced by a violent kind in the above-mentioned parts. Ulceration is more frequently met with upon mucous surfaces than adhesions. Then again, the cellular tissue appears to be much more susceptible of the adhesive inflammation than the adipose, and much more readily passes into the suppurative, Thus we see the cellular tissue connecting the muscles together, and the adipose substance to the muscles, inflaming, suppurating, and the matter separating the muscles from their lateral connections, and even the fat from the muscles, while the latter substance and the skin are only highly inflamed. With respect to fat being inflamed, however, the expression is not strictly true, because fat has no vessels, principle of life, nor action of its own; consequently we cannot suppose that it can itself either inflame or suppurate. We know that it is itself a secretion, and when an abscess forms in it, we understand that the mode of action in the vessels naturally destined to deposit fat has been altered to that adapted to the formation of pus. When, therefore, the fat is said to he inflamed, it is only meant that the membranous cells in which it is contained, and by which it is secreted, are thus affected. The deeply situated parts of the body, more especially the vital, readily admit of the adhesive stage of inflammation.

The circumstance of deeply-seated part3 not so readily taking on the suppurative stage of inflammation as the superficial ones do, is strikingly illustrated in cases of smooth extraneous bodies, which, if deeply lodged, only produce the adhesive inflammation. By this process a cyst or sac is formed, in which they lie without much inconvenience, and they may even gradually change their situation without disturbing the parts through which they pass; but no sooner do these same bodies approach the skin, than abscesses form immediately.

Now, all inflammations attended with disease partake of some specific quality, from which simple inflammation is entirely free. When the constitution allows the true adhesive and suppurative stages to occur, it is to be regarded as the most healthy; for were it in an opposite state, we should see the very same irritation excite some other kind of inflammation, such as the erysipelatous, scrofulous, etc.

In specific inflammations, the position, structure, and distance of the part affected from the source of the circulation, as well as from the surface of the body, seem also to have much influence. Let us now proceed to discuss the symptoms, nature, and causes of inflammation.

Redness, swelling, heat, pain, and loss of function are the five principal symptoms of phlegmonous inflammation. If we refer to any writer on this interesting subject, we shall find the above symptoms enumerated as characterising phlegmon (or healthy inflammation); in short, this term is usually applied to a circumscribed tumour, attended with heat, redness, tension, and a throbbing pain. These are the appearances first observed; and when they are slight, and inflammation is of no great extent, they have commonly very little, and sometimes no apparent influence on the general system. But when they are more considerable, and the inflammation becomes extensive, a full, quick, and generally a hard pulse takes place, and the patient at the same time evinces universal heat, thirst, and other symptoms of fever, while the inflamed part becomes red, painful, and swollen, and its functions are also impaired. The same degree of inflammation produces more swelling in soft parts, and less in those of a harder structure, while of textures naturally transparent, inflammation usually produces opacity.

Most commonly it thickens parts and renders them more solid, hut in certain instances it may occasion the opposite effect, a softening of them, as in the brain and medulla spina-lis. The softening of some textures is regarded by Professor Carswell as a variety of gangrene.

In discussing inflammation it is necessary to remember the febrile disturbance of the constitution. I will therefore now offer a few particulars upon the subject.