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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    warmer flow of blood through them, and so indirectly causes a paresis of the muscular coat. At a temperature of 500 to 6o° the hyperaemia gives place to slight degrees of inflammation. We have here an irritant which, according to the extent of its action, causes either muscular paresis or injury to the vessel walls. To this class of irritants the rubefacients belong, as do also the mineral acids, iodine, mercury, &c. We may class the erythemata caused by inoculation of poisonous substances given off by insects (bees, wasps, &c.) in this group. The aetiology of the infective hyperaernias is still doubtful. They show no relations to the anatomical arrangements of the cutaneous blood-vessels. The closer we examine these exanthemata (scarlet fever, measles, typhoid rash), the more we are convinced that each of them has characteristics of its own, dependent upon a particular infective germ. IV. Obstructive Hyperemia.1 The author has defined relaxive hyperemia as a congested condition of the skin, in which the resistance in the peripheral vessels is abnormally small while the blood- current is quickened. By obstructive hyperaemia he understands a condition of increased vascularity, in which the resistance is abnormally increased while the blood-current is slowed. The increase of resistance which causes congestion may occur at any point in the circulation, in the right or left heart, in the arteries or veins. Congestive hyperaemia of the skin is, however, more simple, and he divides it into two classes according to the general or local character of the congestion. A dark bluish colour and an objective, sometimes subjective, lowering of temperature, are characteristic of all 1 Stauungshyperarnie, ' Monatsh. f. prakt. Derm.,' Bd. ix, 1899, No. 8.