Selected monographs on dermatology / Unna, Nielsen, Duhring, Bronson, Blanc, Berger, Prince-Morrow.

  • New Sydenham Society.
Date:
1893
Catalogue details

Licence: Public Domain Mark

Credit: Selected monographs on dermatology / Unna, Nielsen, Duhring, Bronson, Blanc, Berger, Prince-Morrow. Source: Wellcome Collection.

Provider: This material has been provided by The University of Leeds Library. The original may be consulted at The University of Leeds Library.

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    desis, and these forms show how difficult it is sometimes to draw the line between the two processes. By cupping, the hyperasmia of stagnation may pass into rupture of the ab- normally distended capillaries ; but the diminution of pressure up a high mountain or in a balloon is not sufficient to cause haamorrhage in the skin, although it may fi'om mucous mem- branes, often, no doubt, from the bursting of the inelastic and superficially dried surface covering. A similar result has been attributed to increased pressure within the vessels, but wrongly so in the case of the skin, for the great mus- cularity of the cutaneous arteries is able to resist the most powerful cardiac action. The case is different if there be great general venous congestion, as during the paroxysms of whooping-cough, epileptic and asthenatic fits, parturition, &c, when small cutaneous vessels may occasionally burst. They are insignificant, however, as compared with those occurring under similar conditions in the conjunctiva, retina, and bi'aiu. Squeezing and suction are, therefore, the most important and certain causes of rupture of the well-protected cutaneous vessels. The causes of rhexis, indeed, are mainly trau- matic. Formerly, too much importance was attached to changes in the vascular walls. Although atheroma and thinning of the wall are doubtless important factors in the case of other organs, the small cutaneous arteries are far more subject to the opposite conditions—endarteritis obliterans and thicken- ing of their walls. The theory of fatty degeneration of the cutaneous vascular endothelium must be received with cau- tion, for the fat globules deposited by the lymph are by no means a sign of a degenerative process. Two kinds of vascular changes, however, remain, which may predispose to hasmorrhage :—(i) Atrophy of the venous walls from pressure, as we see now and then in old varices, and (ii) an imperfect embryonic nature of the cutaneous vessels. The first causes not only profuse haemorrhages, but also circumscribed ecchymoses in old people, whose skin is already atrophic. Arrested vascular development often gives rise to hasmorrhage from tumours, especially the sarcomata; but here there is also considerable dilatation of