Selected monographs on dermatology / P.G. Unna [and others].

Date:
1893
Catalogue details

Licence: Public Domain Mark

Credit: Selected monographs on dermatology / P.G. Unna [and others]. Source: Wellcome Collection.

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    If, on the other hand, a sudden obstruction to the venous circulation arises (as in urticaria, where abnormal nervous impulses raise the tone of the veins), a tense elastic swell- ing results, which is sharply defined from the surrounding tissues, because the normal lymph-spaces only allow a small amount of the fluid to be carried off. In cases of extreme oedema, when the cutis is thin, blebs form in the epithelium, which burst, and allow of a constant trickling of lymph (lymph scrotum). The pressure of the fluid may cause necrosis in cases when the skin is greatly thickened. The secretory functions of the skin in all mechanical cedemas are suspended. The surface is dry, fatless, dull, and often slightly desquamating. In the simple oedema of heart and renal disease, only symptoms of pressure atrophy show themselves. The skin becomes thinner, the elastic and muscular tissues atrophy, fat disappears, and the veins and lymphatics become dilated. From this the author thinks that the well-known hyper- plastic processes in elephantiasis nostras and Jilariosa, as well as in long-standing, artificial, inflammatory cedemas, are not consequences of the oedema, but of the preceding inflam- matory changes (erysipelas, eczema, dermatitis artijicialis). In the course of these the skin swells enormously ; the collagenous network grows to a great size ; the epidermis of the skin and follicles• forms deep depressions and warty outgrowths; the blood-vessels and lymphatics become not only thickened, but, as their twisting shows, also elongated; the hyperplastic process extends to the swollen glands. These changes are ascribed to an infective cause; simple mechanical oedema, like venous congestion, is associated with retrogressive changes in the tissues. VI. HEMORRHAGE.1 Haemorrhage in the skin may occur per rhexis or per diapedesis, being blood effusion in the one case, and blood