g 66).

[Illustration: FIG. 66.--Gutter Fracture of the second degree.
Perforating the skull in the centre of its course. External table alone
carried away at either end.]

Bevelling at the expense of the outer table at both entry and exit ends
of the course existed, but in either case a portion of the inner table
was also detached and depressed. Sometimes the depressed portion of the
inner table was mainly composed of one elongated fragment; this was
either when the bullet had not implicated a great thickness of the outer
table, or had passed with great obliquity through especially dense bone
(see fig. 70). When the bullet had passed more deeply the inner table
was comminuted into numberless fragments. I have frequently seen 50 or
60 removed. Where such tracks crossed convex surfaces of the skull, the
two conditions were often combined; thus at one portion of the track,
usually the centre, the comminution was extreme, while at either end a
considerable elongated fragment of inner table was often found, the
latter perhaps more commonly at the distal or exit extremity (fig. 67).

[Illustration: FIG. 67.--Diagrammatic transverse sections of complete
Gutter Fracture. _A._ External table destroyed, large fragment of
internal table depressed. (Low velocity or dense bone.) _B._ Comminution
and pulverisation of both tables centre of track. _C._ Depression of
inner table (low velocity)]

The nature of the injury to the bone when the flight of the bullet
actually involved the whole thickness of the calvarium was comparable to
that seen in the case of the long bones when struck by a bullet
travelling at a moderate rate (see plate XIX. of the tibia, or what is
illustrated in the case of the pelvis in fig. 55). In point of fact, a
clean longitudinal track appeared to have been cut out. The length of
these tracks naturally depended upon the region of the skull struck.
When a point corresponding to a sharp convexity, or a sudden bend in
the surface, was implicated, an oval opening of varying length in its
long axis was the result; when a flat area, as exists in the frontal or
lateral portions of the skull, was the seat of injury, a long track was
cut.

_Superficial perforating fractures._--These formed the next degree; the
chief peculiarity in them was the lifting of nearly the whole thickness
of the skull at the distal margin of the entry, and the proximal edge of
the exit, openings; the flatter the area of skull under which th