ules containing such serum. "These globules have much resemblance to granular cells or exudation corpuscles; but they are larger, and are more distinctly and constantly provided with a cell-wall and nucleus, in addition to granules and molecules." In form, they are generally "spherical," though "sometimes irregularly rounded or oval. Their cell-wall is commonly opaque and somewhat uneven, from being studded with minute granules." "Pus globules are," in general, "larger than exudation corpuscles, even exceeding in size the blood-discs. According to Mr. Addison, they measure from 1-2000 to 1-1500 of an inch." They are evidently a modification of exudation corpuscles.

Physically, pus globules are without great power of cohesion. In this respect, they are in contrast, with the primordial cells and the red corpuscles. This physical effect, however, is, doubtless, the result of a chemical change.

The circumstances which give rise to suppuration are mainly three; an increase of inflammation, an irritating influence of air, and a certain depraved condition of the blood. It is easy to illustrate, at least in part, the manner in which these circumstances produce their effect, and increase the oxidation of the material concerned. It is, however, only necessary for me here to say, that it belongs to the nature of inflammation to expose the affected part to the reception of more oxygen; the pressure of the air does the same directly, and likewise increases the inflammation; and a certain depraved condition of the blood irritates and tends to the same result.

All these influences, where the vital powers are at work, feebly and under embarrassments, are sufficient to give chemical laws the ascendency over vital, and thus to produce the effect, of degenerating and destroying the imperfectly organized material which is about to form a temporary tissue. But, when once that tissue is formed, especially, when the more perfect organization of permanent tissue is produced, it is not to be expected, that the kind of chemical influence referred to can be made to overcome vital influences. In this view of the subject, we perceive, that to speak of pus as a secretion, is not philosophically correct. Liquor sanguinis is secreted, and subsequently undergoes vital changes, upon the surface. Indeed, if a surface which is suppurating be fre

quently sponged, a thin fluid only will, from time to time, be discovered, and no pus, as such, will be seen. The simple reason is, it has not time to form.

What has thus been said of the nature of suppuration throws important light on the question how the absorption of pus produces hectic fever. In the first place, the loss of vitality in what is absorbed renders it foreign matter; and that, when absorbed, always produces more or less constitutional disturbance. In the next place, the increased size of the pus globules must render them exceedingly irritating in their forced passage through the capillaries. And, finally, the soluble tritoxide of proteine, which is a prominent part of pus, acts, chemically, as an irritant. It will even dissolve dead animal matter; and it, doubtless, has an injurious effect, wherever it travels in the human system.

CHAPTER VIII.
ULCERATION.

In ulceration there is a breaking-down and removal of tissue, essentially in the same manner as in mortification. The loss of vitality, in the part, however, is gradual; and, at the same time, there is, in immediate proximity to the decaying part, a struggling and partially successful effort of vitality. By this effort, granulations are being formed, though they are also being disintegrated, in part, and converted into pus.

In the case of an abscess, the hyaline fluid forms an organized or exudation membrane, around a limited part, and thereby defends the exterior structure from the noxious influence of the gathering pus. This membrane has been called pyogenic, on account of its supposed office of secreting pus. We have seen, however, that pus is not a secretion. Still, the name, for distinction's sake, may well enough be retained. This pyogenic membrane varies somewhat, in its strength and influence, according to circumstances. Very commonly, it affords the least resistance in the direction of some cutaneous or mucous surface, and the abscess is said to point in that direction. The parts there are put more upon

the stretch, the vessels are more obstructed, the vitality is diminished, and the liquor sanguinis is less secreted. Fibrous and other hard textures generally resist pretty fully the progress of abscesses and the escape of pus. "Serous membranes, by their ready plastic process, first adhere together, and then often give passage to the contents of an abscess through them," thereby forbidding the escape of any pus into the sacs which they form. After an abscess has opened and discharged its contents, the granulation process, to an extent, gets the ascendancy of the morbid chemical influences; and, though the superficial layer of exudation corpuscles degenerates, more or less, into pus, the healing process is, in time, effected, and the cavity is obliterated.

Sometimes ulcers form superficially. Inflammation gives origin to the destruction of the tegumentary, and portions of deeperseated tissues. They lose their vitality, and are either absorbed or carried away with the pus discharged. The excavation being greater, in some portions than in others, often gives a ragged form to the ulcer. Sometimes, especially when the impurity of the blood enfeebles the vital power, the reparative process will go on but imperfectly, and the pus discharged, or a portion of it, will not be well-formed. It may be ichorous or sanious, or may, by other characteristics, show the weakness of the vital action; but, as soon as the vital energies, working by fixed laws, begin to get the ascendancy, well-formed pus takes the place of that of other traits, and granulations, to a greater or less extent, restore the part.

In general, ulceration has its origin in a suspension of the normal nutrition of the part, by means of inflammation. Frequently, however, it is immediately preceded by an induration which is produced by some abnormal deposit, either from the blood vessels, or from the lymphatic system, or from both. In this case, "the ulceration commences in the centre of the induration, because the nutrient influence of the vessels is most reduced, by the pressure at that spot." Sometimes, it would seem, that the impoverished and impure condition of the blood gives rise to ulceration, without its being preceded by induration or inflammation. This especially happens in parts, the blood vessels of which become congested by posture; and in the non-vascular textures, which are not nourished the most directly by the blood.

CHAPTER IX.

MORTIFICATION.

Mortification consists in the decay of animal tissue, in consequence of a suspension of circulation in the part, or of the blood's having, in a great degree, lost its vital properties. The part dies; and, if the vital energies in the parts immediately around are sufficiently energetic, the reparative process is immediately set up, and, by means of it, the dead portion is separated or sloughed from the living. If, however, the vital power in the surrounding parts is but feeble, and the separating process takes place but slowly, decomposition will, to an extent, ensue, while the dead portion. remains attached to the living.

For convenience's sake, degrees of mortification have been expressed by different terms. When the death of the part seems entire, when the color is a dark bronze or almost black, and when sensible decay is going forward, the mortification is called sphacelus. On the other hand, when vitality seems gradually to depart, • when the color is only livid or a greenish yellow, and when decay is not yet sensible, the mortification is called gangrene. These terms, however, are not always used with precision.

When the vital energies have been sufficient to cause a sloughing of the mortified part, immediately the granulating process will appear, attended with suppuration. Sometimes, when a part is gangrenous, and even when its mortification seems almost entire, it will be, in a measure, supplied with warmth and moisture from the healthy adjoining tissue, it will exhale an offensive odor, and, if it be upon the surface of the body, the cuticle will run in blisters. At other times, the mortified portion becomes dark-colored, dry, and horny, but does not rapidly putrify. It is then called dry mortification or dry gangrene.

When the mortification is internal, as the matter becomes putrid, it is liable, by being pent up, to affect the living body and produce constitutional symptoms. If, however, the constitution be vigorous, and the reparative process be well established, the living parts will be more or less protected from the infectious influence of the

dead matter; but, in persons of feeble constitution, whose blood is deficient in plastic power, the infection will be felt, and typhoid or putrid symptoms will appear. And, in general, it may be said, that no living parts, however great their activity, can long resist the pernicious influence of dead matter in connexion with them, without experiencing a poisoning or injurious effect.

CHAPTER X.

LYMPHATIC SWELLINGS.

Besides the enlargements produced by inflammation and serous effusion, there are forms of swelling which arise from an accumulation of lymph in the part. The lymph is detained in the lymphatic vessels, and over-distends them. Of course, the part is enlarged.

Such an enlargement, when it exists simply, may be called lymphatic congestion. In some cases of ague, nervous swelling, &c., the enlargement is little more than congestion of the lymphatic vessels. When, for instance, the face suddenly swells, in consequence of diseased teeth and a disordered condition of the nerves connected with those teeth, the effect is evidently lymphatic congestion. So, too, when the abdomen suddenly puffs up, by means of disordered uterine action, the puffiness is immediately caused by lymph detained in the lymphatic vessels. The nerves connected with this set of vessels, become weakened in their power, and the lymph does not pass with its normal rapidity; -it accumulates in the part affected. Such, at least, is my view of this matter.

There are, however, modifications of this condition. Not unfrequently, lymph is detained in the glands, until it becomes hardened and assumes a pasty appearance. Inflammation is set up in and around the glands, and so the enlargement is compound in its character. It arises partly from lymphatic congestion, and partly from inflammation. Scrofulous enlargements of glands about the neck, in the axilla, in the groin, and in other localities, are instances of this compound character of disease. So, also,