Medical Jurisprudence, Forensic medicine and Toxicology. Vol. 1

by R. A. Witthaus; Tracy C. Becker

Fig. 7.—Stab-Wounds caused by an Eight-Sided Sharp-Edged Instrument. Some show a transition stage to wounds made by a conical instrument.

Ecchymosis.—This is characteristic, as a rule, of contused wounds. It consists in the infiltration of blood into the tissues, especially the cellular tissues. The source of the blood is from the rupture of blood-vessels, and the size of the ecchymosis varies partly with the number and size of the blood-vessels, or with the vascularity of the part. The size of the ecchymosis also varies with the looseness of the tissues into which it is infiltrated. This looseness of the tissues may be natural as in the scrotum and eyelids, or it may be due to the attrition of the tissues caused by the blow. An ecchymosis is larger when the contused parts cover a bony or resisting surface, and there may be no ecchymosis whatever, even from a severe blow, where the underlying parts are soft and yielding, as is the case with the abdominal parietes. Here we may have rupture of the viscera without any signs of ecchymosis superficially. An ecchymosis may be infiltrative or it may mostly occupy a cavity usually formed by a traumatic separation of the tissues; this is especially the case in the scalp and extremities when the injury is severe. These tumors, which are called hematomata, may be rapidly absorbed or they may remain a long time and occasionally suppurate. Sometimes the anatomical conditions, especially of the connective-tissue spaces, allow the extension or migration of the ecchymosis under the action of gravity, even to a considerable distance. When it meets an obstacle it accumulates above it, as in the inguinal region for abdominal ecchymosis and at the knee for those of the thigh. The course along which the ecchymosis travels is indicated externally by a yellowish stain, soon disappearing, so that soon no sign persists at the site of injury, but only below where the blood is arrested.

An ecchymosis becomes visible at varying times after the injury according to the depth of the ecchymosis and the thinness of the skin, for the ecchymosis is mostly beneath, not in the skin. If the ecchymosis is superficial it shows in one or two hours or even in less time where the skin is very thin, as in the eyelids and scrotum. In such cases it increases for thirty or forty hours and disappears in a week, but may last longer, i.e., as long as fifteen to twenty-five days.

An ecchymosis may not show at the point struck, at least not until several days have elapsed, or it may only show on the under surface of the subcutaneous fat until it has imbibed its way, as it were, to the surface. This may explain the discrepancy in the description of an injury examined by two medical experts at different times.

If an ecchymosis is extensive and deep, especially if it occupies a cavity, there may be nothing to see in the skin for four or five days, and then often only a yellowish discoloration instead of a dark blue color. In such cases, too, the appearance in the skin may be more or less remote from the injury, having followed the course of the least anatomical resistance. Between these two extremes, an ecchymosis may become visible at almost any time. Rarely an ecchymosis occurs only deeply between muscles (pectorals, etc.) and not superficially at all.

The extravasation of blood which forms an ecchymosis has sometimes been given different names, according to its extent or position, for instance, parenchymatous or interstitial hemorrhages or apoplexies, suffusions, ecchymoses, petechiæ or vibices. All such may, however, be called ecchymoses or hematomata. When blood is effused into the serous cavities of the body, special names are sometimes applied according to the position, such as hemothorax, hematocele, etc.

The color of an ecchymosis is at first a blue-black, brown, or livid red. This color changes first on the edges, later in the darker centre, and becomes in time violet, greenish, yellow, and then fades entirely. This change in color is owing to a gradual decomposition of the hæmoglobin of the blood. We can tell the age of an ecchymosis from its coloration only within rather wide limits, for the rapidity of change of color varies widely according to a large number of circumstances, especially according to whether the ecchymosis is superficial or deep. We can only say that the first change, i.e., that to violet, in a superficial ecchymosis, occurs in two or three days.

As an exception to the above color change, we may mention subconjunctival ecchymosis, which always remains a bright red, as the conjunctiva is so thin and superficial that the coloring matter of the blood is constantly oxidized.

The form of an ecchymosis often reproduces well enough that of the instrument, except if the latter be large it cannot all be equally applied to the surface, and its form is not distinctly shown by that of the ecchymosis. After its first appearance an ecchymosis spreads radially, the edges becoming less clear. This change occurs more rapidly the looser the surrounding tissues, and at the end of a few days the first form of an ecchymosis may be changed, so that an examination to determine the nature of the weapon should be made as early as possible.