d at the
proximal margin, while the wound is liable to undergo secondary
enlargement at the distal margin, since in the former the epidermis is
mainly affected, while in the latter the epidermis is spared as an
ill-nourished bridge, the deeper layers of the skin suffering the more
severely. When the wound occurs in regions, such as the chest-wall or
over the sacrum, where the skin is firmly supported, the oval openings
are often very considerable in size, reaching a diameter at least double
that of the circular ones. In the case of the oval openings the
depression of the margins is not such a well-marked feature as in wounds
resulting from rectangular impact of the bullet, since the distal margin
is really lifted.

[Illustration: FIG. 19.--Oval Entry Wound over third sacral vertebra.
Exit wound, anterior abdominal wall. Slightly starred variety. Diagram
made on second day]

_Aperture of exit._--The wound of exit in normal cases offers far more
variation in appearance than that of entry, this variation depending on
several circumstances: first, the want of support to the skin from
without, and such other factors as the degree of velocity retained by
the travelling bullet, the locality of the opening, and the density,
tension, and resistance offered by the particular area of skin
implicated.

When the range has been short and the velocity high, it is often
difficult to discriminate between the two apertures. Both may be
circular and of approximately the same size, and the only distinguishing
characteristic, the slight depression of the margin of the wound of
entrance, may be absent if any time has elapsed between the infliction
of the injury and examination by the surgeon. One very strong
characteristic if present is the general tendency of the margins, and
even the area surrounding the exit wound itself, to be somewhat
prominent. Fig. 16 shows this point, although the wound from which it
was drawn had been produced thirty-six hours before death. The specimen
was then hardened in formalin and still preserves its original aspect.
This character is, however, more frequently displayed in wounds received
at mean, or longer, ranges. In wounds produced by bullets travelling at
the highest degrees of velocity it is often absent.

[Illustration: FIG. 20.--Circular Entry back of arm; exit (bird-like) in
anterior elbow crease]

[Illustration: FIG. 21.--Circular Entry over patella. Starred exit of
elongated form in popliteal