The causes which particularly favour the occurrence of haemorrhage are: 1. External heat, which is said to rarefy the blood: but the blood is by no means an expansile fluid; and the swelling of the veins, in warm weather, alleged as an argument of its expansility, is owing to the diminished resistance of the integuments. Sauvages and Haller inclosed blood in a thermometrical tube, and found that in the heat of boiling water it did not dilate 1/200 Part of its bulk. When, therefore, heat assists the production of haemorrhage, it is rather by diminishing resistance, and increasing the irritability, which disposes to irregular action. 2. A sudden diminution of the weight of the atmosphere is said to have the same effect, and the facts adduced in its support are the bleedings from the lungs in ascending high hills. Later experience seems not to have confirmed this opinion, but to have attributed the haemorrhage to the difficulties of the ascent, in lungs previously weak, since the accident is chiefly confined to such habits. 3. Violent exercise and violent passions certainly contribute to the production of haemorrhage, particularly exercise of some organs, as of the voice, in producing haemoptysis. 4. Ligatures, on particular parts or postures favouring a particular determination of the fluids. 5. Cold, particularly if applied suddenly to the lower extremities.

The first question to be considered when we are to speak of the cure of hemorrhages is whether they are to be left to the regulations of nature, or be relieved by art. Dr. Stahl and his followers thought discharges of blood owing to the exertions of nature to remove an habitually plethoric state, and that when the vessels were sufficiently depleted the wound would close. We have admitted that when faintness came on, the haemorrhage would cease; but it is highly proper not only if pos-; sible to prevent the occurrence, but to diminish or check the discharge. We cannot allow that nature, if all powerful, is all wise. If a person is plethoric she will sometimes discharge the load on the brain, sometimes on the lungs, where immediate death may ensue, instead of the stomach, where the blood would not be injurious. She does Hot when the plethora is removed prevent its recurrence, but stores up fluids for a return of the disease. In short, as in many other situations, nature must be superseded or checked in her operations, and haemorrhages cured by art; for a recurrence, against which she has not provided, will occasion hydropic swellings; and in the lungs, her most common outlet, a consumption may be the consequence.

The chief foundation of what may be styled the haemorrhage diathesis is plethora. It is necessary for various purposes of the animal economy that the arterial system should be kept full, and even distended. The arteries are kept full, whatever be the quantity of fluids, by the elasticity of their external coat, and the contractility of the muscular: they are kept distended by that portion of the fluids necessary to counteract this elasticity and contractility. Fulness is therefore relative: when only in that degree which excites a proper tone it is salutary; when beyond, it is morbid tension. So necessary is a fulness of the vessels, that nature is always anxious to keep it to the proper degree, and even in excess. Plethora is consequently the most frequent morbid state, and haemorrhages very frequent diseases. The means of relieving plethora, while constantly counteracted by nature, are not easy. Fluids evacuated either by nature or art are soon supplied, as we have said, by the stoppage of the secretions; and consequently bleeding, the most obvious means, is only a temporary relief. It is a suspicious one, as the quantity is soon restored; and it is injurious, as laying the foundation of a habit which cannot, with advantage be always obviated, or without danger neglected. It is, however, often absolutely necessary, to prevent fatal consequences; for suddenly to deplete will alone occasion that faintness to which the cessation of the discharge is most commonly owing. A more certain method of obviating plethora is by diet, and increasing the excretions. Though nature constantly keeps the vessels full by regulating the secretions, yet it depends on ourselves neither to fill the vessels rapidly with the most nutritious fluids, nor to keep them distended by inactivity. A light vegetable diet does not produce nourishment, either copious in quantity or rich in quality; and it prevents plethora, by being at the same time cooling and laxative. With this diet, moderate exercise is useful; and this is perhaps only contra indicated in haemoptysis. Exercise, while it fills the vessels of the surface, whose united areas we have found to be considerable, promotes that insensible discharge which we have shown to be so highly salutary; and if conducted so as not to increase the vital heat, or accelerate the circulation, is highly useful. Another equally obvious method of avoiding plethora is by laxatives. These should be mild and gentle; of that kind which excites the discharge from the excretories, rather than that which stimulates the muscular fibres of the intestines. The neutral salts are particularly valuable in this view. Of the other evacuants we cannot speak highly as obviating plethora, though the topical ones which obviate partial plethora are of singular utility. These are cupping glasses, leeches, setons, issues, and blisters. Each acts by drawing the fluids to the surface: each by partially evacuating them. In this general view we need not enter into their comparative merits, and perhaps on the whole a preference cannot be easily assigned. Neither acts with rapidity, except perhaps the cupping glasses, and they are prophylactic rather than curative remedies. A very effectual method of curing haemorrhages is by moderating the impetus of the blood, on which they so greatly depend. The first medicines to be employed are refrigerants; and the most effectual of these is cold water, internally; occasionally with frequently repeated, rather than large, doses of nitre. The latter is a remedy of the greatest importance; an"instar omnium" in these complaints, especially when saline purgatives are interposed. External cold is equally useful;