2d. Punctured wounds by instruments both sharp pointed and cutting, like a knife or dagger. If these wounds are perpendicular to the surface, they have more or less the form of the weapon used. The angles may show whether the knife, etc., had one or two cutting edges, but even though the back of the knife is broad the wound may resemble one caused by a double-edged weapon. Thus stab-wounds from a common pocket-knife show only exceptionally a wedge-shape, but regularly a slit, the edges of which are slightly curved to one another and end in two acute angles. The reason of this lies in the fact that the wound is only caused by the cutting edge of the knife, so that we cannot tell as a rule which angle was occupied by the back of such a knife (Figs. 4 and 5). The depth of these wounds may equal the length of the weapon or be almost any degree less, but the depth may even be greater than the length of the weapon by reason of a depression of the parts at the time of the blow. The wound is often shorter and broader than the weapon causing it, though more often it is larger than the weapon from the obliquity of the wound and the movement of the weapon on being withdrawn. The wound is smaller than the instrument where the parts are on the stretch at the time the wound is inflicted.
Fig. 5.—Nine Suicidal Stab-Wounds in the Region of the Heart made by a Knife used for Cutting Rubber.
This variety of punctured wounds may resemble the former class in the direction of its long axis, if the cutting edge of the instrument is blunt. The regularity and smoothness of the edges distinguish them from certain contused wounds.
3d. Wounds made by instruments with ridges or edges, files, foils, etc. If the edges are cutting the wound presents more or less the shape of the weapon (Fig. 6). But this is not always so, probably from the instrument puncturing obliquely or from the tissues being unequally stretched (Fig.7). If the edges are not cutting the wound resembles those of the first class, though the edge often presents little tears, and the wound may thus be more or less elliptical with two unequal angles. The wound of entrance and exit may be different.
Fig. 6.—Stab-Wounds caused by a Three-Sided Sharp-Edged Pointed Instrument.
4th. Irregular perforating instruments, the wounds from which resemble contused wounds.
Contusions and Contused Wounds.—A contusion is a wound of living tissues by a blow of a hard body, not sharp-edged or pointed, or by a fall, crushing, or compression, and without solution of continuity of the skin. A contusion usually involves a moderately large surface in comparison to the two other classes of wounds. Contusions are of all degrees of severity. If the blow or injury is slight, there is only slight redness and swelling of the skin with pain, disappearing in a few hours, and leaving no traces. If the blow be harder it produces more or less crushing of the tissues, accompanied by ecchymosis with or without a wound or excoriations of the skin, etc. The contusion may have the shape of the contusing body, such as a whip, the fingers, etc.