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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    produce at will below a venesection bandage ; and Auspitz first showed us, by his stagnation experiments, that venous congestion alone suffices to produce macroscopic haemorrhages, even in healthy skin. The congestion must border on stasis, but in certain diseased conditions lesser degrees of conges- tion suffice. In scarlatina and erysipelas a purpuric erup- tion is easier induced than with the normal skin ; and still more so in a acute dermatitis, acute eczema, urticaria, and measles. Cutaneous haemorrhage is enormously increased by simple congestion in the case of purpura variolosa, the whole limb showing a suffused black colour. In one cate- gory of cases under this group the stasis of blood in the larger veins is the sole cause of the haemorrhage, as in the rare petechia? after thrombosis, e. g. in phlegmasia alba dolens. Extravasations in varicose legs, although belonging to the same class, are not so easy to explain. Varices are not due simply to gravity, but to a chronic gravitation-hyper- aemia in connection with an increased tone of certain vessels of the limb, and consequent diminution of the vis a tergo. Extravasation is the result, especially where the skin is atro- phic, as in the neighbourhood of chronic ulcers. The pre- agonal purpura, developed on dependent parts shortly before death, is related to this. It originates from the general venous congestion and gravitation-hyperaemia caused by deficient vis a tergo, and is an example of so-called cachectic pur- pura. Here, too, spasm of the small cutaneous veins so resists the pressure in the venous capillaries, that diapedesis of red disks can take place. This is also the case in very chronic urticaria, urticaria perstans (Pick), erythema multiforme of the legs, purpura urticans, and in lichen lividus of old people. Bateman's purpura senilis may be here mentioned, which occurs chiefly on the extensor surface of the forearm in old women, and is very chronic and accompanied by dark pig- mentation. The larger group of infective and toxic pelioses were formerly explained by blood-dissolution, the poison being supposed to produce so profound a change in the blood that it passed easily through the wall of the vessels, as in purpura variolosa and severe yellow fever. This idea is erroneous: before such a diapedesis of red discs, considerable oedema