of the special joints to illustrate this point. Danger only
arose in the event of suppuration; and here the presence of the long
oblique superficial track in a neighbourhood liable to comparatively
free movement was the important element. Such tracks usually opened the
synovial sac more extensively than direct perforating wounds, and if
suppuration occurred in any portion of the track, the pus was very
liable to be sucked into the joint on any free movement. The presence of
fine splinters of the bone displaced in the production of the groove was
also a special character of wounds of this class. Another point worthy
of mention is that in these cases it was not always easy to be quite
certain whether the joint cavity had been implicated or not, since cases
often occurred in which, although the bones had been grooved, the joint
cavity escaped. The indication, however, was to consider any wound in
the immediate proximity of a joint as perforating until it was healed.
This course was the more easy to take, since a large proportion of such
wounds were accompanied by some degree of synovial effusion, even when
the neighbouring joint had escaped puncture.

Wounds of the fourth class, although the most highly characteristic of
the form of accident, were in many instances the most favourable in
regard to their course. The tracks might course directly across the
joint in any direction, or they might course obliquely, traversing
either one or both the component bones. In the latter case the exit
might be in the diaphysis, and be accompanied by the separation of an
exit fragment such as is illustrated in fig. 52, p. 169. The
particularly favourable character of the direct transverse and
antero-posterior wounds depended on the slight amount of splintering of
the bones, the limited nature of the opening into the joint, and the
shortness of the tracks in the soft parts, which ensured that, even if
infection did occur, the resulting pus was near the surface, and
generally spread in that direction and escaped.

Wounds of the fifth class were the most dangerous, but the danger was
entirely a secondary one, dependent on the occurrence of infection.
These injuries were liable to be accompanied by the presence of
extensive irregular wounds of the soft parts, in which suppuration was
frequent, and the suppuration of the joint frequently meant subsequent
amputation, if not a worse result.

_Course and symptoms of wounds of the joints._--The