of
fracture, where the vibrations are rendered still more far-reaching and
effective as the result of their wider distribution from the larger
solid resistance afforded by the bone. The relative density and
resistance offered by the different parts of the bone acquire great
significance in this relation, since local shock due to nerve concussion
is far more profound when the shafts are struck than when the cancellous
ends furnish the point of impact.

The form of concussion which most nearly interests us in this chapter is
that affecting single nerve trunks in wounds of the soft parts alone,
and here the passage of the bullet is, as a rule, so contiguous to the
nerve that there is difficulty in drawing a strict line of demarcation
between such cases and those dealt with in the next paragraph.

II. _Contusion._--Clinically this was the form of nerve injury both of
greatest comparative frequency and of interest from the points of view
both of diagnosis and prognosis.

The seriousness of a contusion depends on two factors: first, the
relative degree of violence exerted upon the nerve, which is dependent
on the force still retained by the travelling bullet; and, secondly, on
the extent of tissue actually implicated. The range of fire at which the
injury was received determines the importance of the first factor; the
second varies with the degree of exactness with which the nerve is
struck, and on the direction taken by the bullet. Naturally transverse
wounds affect a small area; while an oblique or longitudinal direction
of the track may indefinitely increase the extent of injury to the nerve
trunk, and hence acquire prognostic significance in direct ratio to the
amount of tissue which needs to be regenerated.

As to the actual anatomical lesion resulting in the cases which we
designated clinically as contusion I can give no information. On many
occasions when the symptoms were considered of such a nature as to
render an exploration advisable, no macroscopic evidence of gross injury
was obtained. It was therefore impossible to draw a definite line of
demarcation between such cases and those which we considered merely
concussion. It could only be assumed that the vibration transmitted to
the nerve had occasioned such changes as to destroy its capacity as a
conductor of impressions.

In some cases the presence of a certain amount of interstitial blood
extravasation was suggested clinically by early hyperaesthesia and sig