Together with those inflammations leading rapidly and insensibly to exudation, the term deposit (metastasis, capillary phlebitis, lobular process) applies aptly to certain processes which, considering the rapidity with which they become established, are, in many respects, of a very remarkable kind. These processes are founded in a sickening of the fibrin, with a tendency to coagulation. They consist in the blood, through spontaneous impairment or through infection [that is, the reception of various substances], acquiring the tendency to coagulate, and actually coagulating within the circulating system, under a more or less marked separation of fibrin.

This happens either in one of the larger vessels, or, what is far more common, in the capillaries of an organ. In the former case it is, consistently with the frequent reception of deleterious substances into the venous blood, the larger veins, usually in the vicinity of the point of infection. With respect to the capillary system, no point of it is exempt, although the more vascular organs, those in which the blood undergoes important changes, are most obnoxious to the affection; for example, the lungs, the spleen, the kidneys.

In large vessels it is not difficult to interpret the appearances. In the absence of all evidence of local inflammation of the vessel's coats, the calibre is plugged with lengthy, cylindrical, or smaller, clod-like - in vascular trunks membranaceous, - in arteries, especially where the inner surface is rough or gibbous, adherent - coagula. The probability of these coagula resulting from inflammation of the vessels, increases in proportion as the fibrin which constitutes them is pure, and as its yellow color and general attributes approximate to those of croupous fibrin. The various coagula found within the heart's cavities - the valvular, the globular, vegetations, belong to the same class.

The cylindrical and clod-like coagula are often equably reddened by incorporated blood-corpuscles. At other times they contain layers of a lighter color than the rest, and which therefore have incorporated fewer blood-corpuscles. Some layers are even marked by a total absence of redness, and obviously consist of pure effused fibrin.

To trace the process in the capillaries is not an easy matter. It is conceivable that besides what happens within the vessels, and as a consequence thereof, exudation of blood-serum, and even of a portion of plasma with blood-pigment takes place. By means of this exudation, the vessels become obscured and uncognizable. Still, the simple fact of the process occurring in large vessels should remove all doubt as to its existence in the capillaries.

In the capillaries of an organ, the process originally manifests itself by a dark red, sometimes reddish-white, spangled or striated, circumscribed, impacted substance, of a dense, fragile consistence.

These impactions possess the peculiarity of being seated for the most part in the periphery of organs, - the lungs, spleen, kidneys, for instance. They represent roundish tubercula or else wedges with their broad base directed towards the periphery and impinging upon the sheath, - their points towards the interior of the organ. They are always present in considerable number, and commonly associated with exudative processes. Their size is mostly inconsiderable, commonly ranging from that of a pea to that of a walnut. In organs of a lobu-lated structure, they are sometimes called lobular metastases.

The ulterior changes are various, corresponding with the nature of the coagulation, and therefore of the blood-(fibrin) disease.

They sometimes shrivel and condense, with obliteration of the canals of the vessels, and of the implicated textures, into a fibroid state, - still further shrivelling callus, towards which the neighboring parts are retracted in a scar-like manner, and which often involves a residue of blood-pigment in the shape of rusty brown, or rusty yellow coloration.

It is probable that, like the thrombus, they are often progressively redissolved, and again taken up into the circulation without detriment to the textures.

Sometimes they break down to a puriform, ichorous fluid, to gangrenous ichor, with diffluence and necrosis of the involved textures, resulting in a pus or ichor depot, or a gangrenous slough. In greater coagula, this metamorphosis very commonly emanates from the central layer. Capillary impactions, at the periphery of an organ, often assume the aspect of a superficial boil.

The coagula often undergo fatty conversion.

Occasionally, the coagula have the character of tubercle or of cancer, especially of medullary cancer; and it is probably through this process that the often very rapid development of cancer is produced in brutes, by the injection of cancer-blastema.

In conclusion, many an important crase-exhausting metastasis may have its source in the same processes, involving a great extent of capillaries, and issuing in gangrene. Such metastases occur as the sequel to typhus, and to the exanthemata.

With respect to the organs whose capillaries are especially obnoxious to these coagula resulting from infection of the blood, as it is in venous blood that the mischief commonly originates, and as the lungs are the first organs reached by the poison, their capillary tissue is commonly the first to suffer. In its arterial passage, the contaminated blood next attacks the capillaries of the spleen, and of the kidneys. Lastly, in a higher grade of the dyscrasis, all the other textures, mucous membranes, common integuments, and subcutaneous areolar tissue, even bone, become implicated in their turn.

In infection of the portal blood, the liver is the first assailed, otherwise it is only so in common with other organs, and by no means more frequently than the spleen and kidneys.

That, compared with the greater vessels, and especially the arteries, these processes occur pre-eminently in the capillary system, seems due to the slackening of the circulation in the capillaries, which in itself promotes coagulation, and at the same time, leaves the deleterious matter longer in contact with the blood. In certain organs, moreover, their formation appears, as before stated, to be favored by the revulsion which the blood undergoes in them during the acts of nutrition and secretion.

Sensitive as is arterial blood in respect to infection, as in arteries, for instance, coagula are comparatively rare in arteries of the aortal system, with the exception of those at the point of arterial inflammation. This is probably owing to the great rapidity of the arterial current. In the arterial section of the heart, however, they are readily engendered by diminished action of their organ, far more readily than out of the venous blood in its right chambers.

The relation which these processes bear to inflammation and its terminations, is obvious. Determined by high grades of dyscrasial impairment of the blood, they represent product formation, endogenous exudation, within the vascular system.