Hemorrhage consists in the extravasation of blood bodily, and in its entirety, from the bloodvessels, consequent upon a breach of their continuity. Herein it differs from red effusions resulting from the transudation through the parietes of vessels of blood serum, which, owing to various changes of admixture, has taken up blood pigment. Hemorrhage occurs either within textures, when it is with reference to its attendant paralysis, somewhat inappropriately termed apoplexy; or else within natural or preternatural cavities or canals; for example, in serous sacs, in muco-membranous cavities or canals, pus-reservoirs, etc. The two kinds frequently coexist.

Heterologous growths are, in the same degree as normal formations, subject to hemorrhage, those at least which are highly vascular; as, for instance, adventitious membranes, carcinoma (in a high degree), the interior of cysts, etc.

Hemorrhage depends upon various causes, the most common cause being, as before stated, a breach of continuity in the bloodvessels.

Apart from hemorrhages produced by external injury inflicted upon bloodvessels, whether alone or in conjunction with other formations, those resulting from the following momenta, more especially capillary (parenchymatous) hemorrhages, possess a high degree of interest.

1. Hemorrhage the result of intense hyperaemia, of whatever kind. Thus, active hyperemia has a marked tendency to create bronchial hemorrhage, passive hyperemia uterine hemorrhages, hyperaemia from mechanical causes, in particular the bronchial and intestinal hemorrhages that result from heart disease, and the cerebral hemorrhages induced by a vacuum within the skull.

Finally, the excessive accumulation of blood determines rupture of the capillaries.

2. Another step conducts us to hemorrhage as occurring during the progress of inflammation, namely, in the stages of congestion and of stasis. In this combination we have hemorrhagic inflammation, and the in many respects remarkable exudation designated hemorrhagic. Here, as in simple hyperemia, the hemorrhage is unfailing, and considerable in proportion to the extent of the congestion and stasis, as also to the delicate, lax, and vulnerable, nature of the implicated texture. Any one of these influences may predominate to a various extent. There are organs in which, owing to the nature of the texture, inflammation never takes place without hemorrhage - for instance, the brain, the lungs, many heterologous formations, and especially exudates undergoing a change of structure, and loose cancerous textures. The hemorrhage is capillary.

3. Hemorrhage from the laceration of vessels, produced in atrophied organs by the laxity and diminished resistance of surrounding textures - apoplexy of the decrepit uterus.

4. Hemorrhage from the spontaneous laceration of organs diseased in texture, pulpy and friable - laceration of the heart.

5. Hemorrhage from laceration of vessels consequent upon impaired texture of their coats, with or without dilatation of their calibre. It affects the smallest bloodvessels as readily as the main trunks, and more especially the arteries. Other coincident causes - hypersemia, for example - greatly favor its occurrence.

6. Hemorrhage consequent upon the destruction of bloodvessels by ulceration, or by contact with a free acid, as in softening of the stomach.

It is questionable whether, and in what way, dyscrasial states can give rise to hemorrhage. A relaxation of the coats of bloodvessels sufficient to admit of the passage through them not only of plasma, but also of blood-corpuscles, is by no means proved, and its assumption, to explain the hemorrhage occurring in scurvy or typhus, needless. The spontaneous hemorrhage arising in the progress of such maladies, is the result either of local hyperemia and inflammation, into which those general diseases have resolved themselves, or else of preternatural expansion (increased volume) of the blood itself, and of the consequent rupture of bloodvessels in the looser textures, such as the gums, the mucous membranes, and the lungs. Hence the occurrence of hemorrhage in several organs simultaneously, and again the predominant invasion of a few particular organs. That hemorrhage, having once set in under such circumstances, is apt to become excessive, is due, without any doubt, to the slender coagulability of the dyscrasial blood.