It is indispensable in the first place to discriminate between exudates reddened by blood-pigment only, and those which contain substantive blood, that is, blood-corpuscles.

The former are met with in all dyscrases, both acute and chronic, in which, owing to defibrination, to decomposition of the fibrin, or to diminished proportion of salts, blood-pigment is transferred from the blood-corpuscles to the blood-serum. Thus, exudates occurring during the progress of scurvy, of typhus, of gangrene, of the drunkard's dyscrasis, of putrid exanthemata, are stained with adherent blood-pigment. Those containing blood in its totality, and the red color of which results from blood-corpuscles, are the true hemorrhagic exudates.

Holding fast this distinction, we shall be enabled partly to infer from physiological reasoning, partly to prove by the exact method, the origin and import of hemorrhagic effusion.

We have seen that, in every inflammation, at the stage of congestion and stasis, there occur extravasations of blood, proportionate in extent to the vascularity of the organ, to the magnitude of its congestion and stasis, and lastly, to the laxity and vulnerability of its texture. That this bleeding takes place out of lacerated, or in somewise opened vessels by extravasation, and not by transudation, is evident from the absence in the walls of bloodvessels of pores equal to the transudation of blood-corpuscles. This is the rule with respect to hemorrhage in textures like those of the brain or the lungs. The difficulty is, and always has been, to explain hemorrhagic effusion occurring upon serous membranes, - a formation so given to effusion in no way hemorrhagic. Upon this point it is to be observed:

(a.) A primitive genuine hemorrhagic exudate (not merely bloodstained), if it really ever occur upon serous membranes, occurs only as a rare exception.

(b.) Hemorrhagic exudates upon serous membranes are, almost without exception, the result of hemorrhage from the bloodvessels of a spurious membrane in the act of becoming organized; in other words, from the product of a previous inflammation of the serous tunic. This hemorrhage may be an independent act, or it may be the concomitant of inflammation propagated from the serous coat to its pseudo-membranous duplicate. This is, in fact, usually the case. Such exudates are secondary ones.

The facility with which hemorrhage takes place from these new growths, is explicable on the ground of their imperfect organization, both as regards change of texture and the development of bloodvessels. An inflammation early set up in such a new formation, encounters a lax, soft, lacerable growth, involving an incomplete, soft, and delicately membraned vascular apparatus, with anastomoses as yet unclosed; bloodvessels which, when urged into congestion and stasis, readiy give way, or possibly force a passage from their free and as yet unanastomosed ends into the substance, and through this into the cavity, of the serous membrane.

Accordingly, under these stereotype conditions, hemorrhagic exudation is precisely what extravasation is during the course of an inflammation in the laxer textures, namely, exudation plus hemorrhage.

Hemorrhage being, however, the consequence not alone of mechanical laceration, but also of a softening or a corrosion of the vessels, it is intelligible how ichorous exudates, and the solvent exudates generally, may put on a hemorrhagic character.

Hemorrhagic Exudation

Hemorrhagic Exudation seems to stand in an especial relation to tuberculosis, and is dreaded chiefly because the latter is assumed to be its source. It is important to be clear upon this point:

(a.) It is quite true that it is very frequently a partially tuberculized new growth (pseudo-membrane) in which the hemorrhagic process occurs. Still there are very notable exceptions to this.

(b.) Tuberculized growths appear to be peculiarly liable to inflammation; tubercle being wont to set up reactive processes of inflammation everywhere in its circumference.

In this way the hemorrhagic inflammatory process often concurs with local tuberculosis, without directly depending upon the tuberculous crasis. That tuberculosis acts as the source of hemorrhagic effusion is rendered probable by experience, but it is by no means proved.

In like manner, hemorrhage and hemorrhagic exudation break forth in the midst of carcinomatous growths, or in pseudo-strata, of the same character, upon mucous membranes or within serous sacs.

In quantity, the extravasate mingling with the exudate varies considerably, and it may be either intimately blended both with the coagula and with the fluid portion of the exudate, or separated from it in the shape of pellet-like clots.

Apart from the aforesaid conditions of its appearance, and of its relation to tuberculosis, it is of evil omen only in proportion to the loss of blood entailed by it, and to the previously reduced vital strength of the patient.

The hemorrhagic exudate is not organizable, or only very tardily so. This refers more particularly to the exudate; the blood-corpuscles after long remaining unaltered at length become dissolved, leaving their pigment to undergo the changes elsewhere described. The exudate portion, answering to the character of its base, very commonly retains its rudi-mental condition, which in the majority of cases is tuberculous.

It would seem advantageous, before concluding, to revert to a few points already touched upon, relative to the habitudes of exudates in and upon diseased structures.

Exudates are deposited more or less uniformly between the elementary parts of textures. This is contingent upon the more or less uniform density and cohesion of the textures, as also upon the number of bloodvessels present, and their mode of distribution; for example, the striated exudates, following the linear arrangement of the bloodvessels in tendons and ligaments.

When copious effusion takes place suddenly and violently in the laxer structures, for example, in the brain, the exudate becomes established through the forcible separation and laceration of the natural textures.

In the inflammation of membranes the exudate is, as we have stated, for the most part thrown out upon the free surface. In the inflammation of glands similar effusion takes place into their respective cavities - the uriniferous tubules, Malpighian bodies, and the like.

Coagulable exudates solidify upon the surface of inflamed membranes, and are commonly termed spurious membranes. Upon serous membranes they occasion agglutination of the serous surfaces.