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Hæmorrhagies happen especially in plethoric: habits, and to persons of a sanguine temperament. They appear most commonly in the spring, or in the beginning of summer.

For some time, longer- or shorter in different cases, before the blood flows, there are some symptoms of fulness and tension about the parts from whence the blood is to issue. In such parts as fall under our view, there are some redness, swelling, and sense of heat or of itching; and in the internal parts, from which blood is to flow, there is a sense of weight and heat; and, in both cases, various pains are often felt in the neighbouring parts.

739. When these symptoms have subsisted for some time, some degree of a cold stage of pyrexia. comes on, and a hot stage is formed; during which the blood flows of a florid colour, in a greater or lesser quantity, and continues to flow for a longer or shorter time; but commonly, after some time, the effusion spontaneously ceases, and together with it the pyrexia also.

740. During the hot stage which precedes an hæmorrhagy, the pulse is frequent, quick, full and often hard ; but, as the blood flows, the pulse becomes softer and less frequent.

741. In hæmorrhagies, blood drawn from a

vein, does, upon its concreting, commonly shew the gluten separated, or a crust formed, as in the cases of phlegmasiæ.

- 742. Hæmorrhagies, from internal causes, having once happened, are apt, ' after a certain in. terval, to return; in some cases very often, and frequently at stated periods.

743. "These are, in general, the phenomena of hæmorrhagy; and if in some cases all of them be nof exquisitely marked, or if perhaps some of them do not at all appear, it imports only, that, in different cases, the system is more or less generally affected ; and that, in some cases, there are purely topical hæmorrhagies, as there are purely topical inflammations.

SECT. II.

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Of the proximate cause of llamorrhagy. 744. The pathology of hæmorrhagy seems to be sufficiently obvious. Some inequality in the distribution of the blood occasions a congestion in particular parts of the sanguiferous system ; that is, a greater quantity of blood is poured into certain vessels than their natural capacity is suited to receive. These vessels become, thereby, preternaturally distended; and this distention, proving a stimulus to them, excites their action to a greater

degree than usual, which pushing the blood with unusual force into the extremities of these vessels, opens them by anastomosis, or rupture ; and, if these extremities be loosely situated on external surfaces, or on the internal surfaces of certain cavities that open outwardly, a quantity of blood flows out of the body

745. This reasoning will, in some measure, explain the production of hæmorrhagy." But it appears to me, that, in most cases, there are some other circumstances that concur to produce it: for it is probable, that in consequence of congestion, a sense of resistance arises and excites the action of the vis medicatrix naturæ; the exertions of which are usually made by the formation of a cold stage of pyrexia, inducing a more vigorous action of the yeşşels ; and the concurrence of this exer. tion more effectually opens the extremities, and occasions the flowing out of the blood.

746. What has been delivered in the two preceding paragraphs, seems to explain the whole phenomena of hæmorrhagy, except the circumstance of its frequent recurrence, which I appre. hend may be explained in the following manner,

The congestion and consequent irritation being taken off by the flowing of the blood; this, therefore, soon after, spontaneously ceases; but, at the same time, the internal causes which had before produced the unequal distribution of the blood, commonly remain, and must now operate the more readily, as the overstretched and relaxed vessels of the part will more easily admit of a congestion of blood in them, and, consequently, produce the same series of phenomena as before,

747. This may sufficiently explain the ordinary return of hæmorrhagy: but there is still another circumstance, which, as commonly concurring, is to be taken notice of; and that is, the general plethoric state of the system, which renders every cause of unequal distribution of more considerable effect. Though hæmorrhagy may often depend · upon the state of the vessels of a particular part being favourable to a congestion's being formed in them; yet, in order to that state's producing its effect, it is necessary that the whole system should be at least in its natural plethoric condition ; and, if this should be in any degree increased beyond what is natural, it will still more certainly determine the effects of topical conformation to take place. The return of hæmorrhagy, therefore, will be more certainly occasioned, if the system becomes preternaturally plethoric; but hæmorrhagy has always a tendency to increase the plethoric state of the sys. tem, and consequently, to occasion its own return.

*1748. To shew that hæmorrhagy does contribute to produce or increase the plethoric state of the

system, it is only necessary to observe, that the quantity of serous fluids being given, the state of the excretions depends upon a certain balance between the force of the larger arteries propelling the blood, and the resistance of the excretories : but the force of the arteries depends upon their fulness and distention, chiefly given to them by the quantity of red globules and gluten, which are, for the greatest part, confined to the red arteries ; and therefore, the spoliation made by an hæmorrhagy, being chiefly of red globules and gluten, the effusion of blood must leave the red arteries more empty and weak. In consequence of the weaker action of the red arteries, the excretions are in proportion diminished ; and, therefore, the ingesta continuing the same, more fluids will be accumu. lated in the larger vessels. It is by this means that the loss of blood by hæmorrhagies, whether artificial or spontaneous, if within certain bounds, is commonly so soon recovered : but as the dimic nution of the excretions, from a less quantity of fluid being impelled into the excretories, gives occasions to these vessels to fall into a contracted state ; so, if this shall continue long, these vessels will become more rigid, and will not yield to the same impelling force as before. Although the arteries, therefore, by new blood collected in them, shall have recovered their former fulness, tension, and force, yet this force will not be in balance with the resistance of the more rigid excretories,,

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