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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    filtration in the other. Although neither the causes, sym- ptoms, concomitant circumstances, nor final results are the same, we cannot in every case say whether a given haemor- rhage has resulted from rupture or from filtration, and to avoid repetition they may be both considered together, under the common term haemorrhage. It is, moreover, obvious that the chief causes of diapedesis may act as assisting causes of rupture of blood-vessels and vice versa. It is, however, important to accentuate the marked differences of the two processes. We can more easily decide, in the case of the skin, whether rupture of a vessel has occurred; and im- bedded, as the latter is, in a firm, tough tissue, haemorrhage from it must always be more difficult, and when it occurs, more easily ascribed to either process than in the case of the vessels of internal organs. When rupture takes place, red blood is poured out through a wound of the vascular wall ; but when the haemorrhage is due to diapedesis, lymph passes through, poor in albumin, fibrin factors, and white corpuscles, but abnormally rich in red discs. In the former case a blood pool rapidly forms in the tissue, its size being determined by the surrounding resistance, and this pool is soon converted into a thrombus; but in the latter case the haemorrhage increases slowly, and its elements are diffused through the neighbouring tissue without becoming a con- tinuous clot. If the haemorrhages are small, these differ- ences may not be detected by the microscope, especially when the specimens have been hardened. Haemorrhages due to rupture may give rise, if small, to ecchymoses, and if large, to blood-boils or haemato- mata. The cause is nearly always some gross traumatic lesion. The flea-bite is an example of the former, and large and more permanent blood suffusions may be produced by blunt force over large areas, without penetration ; the result in this case depending more on the actual vascularity of the skin at the time. Hence, all factoi*s producing stagnation hyperaemia increase the liability to haemorrhage from rup- ture. One kind of blood-boil is the ot-haematoma of lunatics ; but the cephalo-haematoma of infants and haematomata of the vulva in parturition do not belong solely to this class, for there is at first a stagnation oedema leading to diape-