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 the bullet travelled the more extensive was the comminution. In some cases nearly the whole length of the bone superficial to the track would be raised; in fact, the bullet having once entered, the force is applied from within in exactly the same way that it operates on the inner table in the gutter fractures. A corresponding injury is met with in the case of the bones of the extremities (see fig. 57 of the tibia), and again the resemblance between these injuries of the skull and such perforations of the long bones as are illustrated by skiagrams Nos. III. and XXIII. of the clavicle and fibula is a close one.