Fractures limited to the internal table.
These fractures are even more rare than those described above. Their occurrence is probably only possible when the bullet strikes the skull in a markedly oblique direction, and with greatly diminished velocity—‘spent’ bullets. I believe I am correct in stating that only one instance of this particular variety of fracture was observed in the South African War. In any case, they are of such infrequent occurrence that they may be practically disregarded.
Gutter fractures.
Gutter fractures are almost invariably dependent on the impact of a glancing bullet. They may be arranged in three groups, according to the extent of the osseous lesion.
1. Where the external table is blown away, leaving the internal table exposed, perhaps comminuted.
2. Where the internal table is driven in the inward direction, pressing on, irritating, and perhaps lacerating the dura mater.
3. Where the whole thickness of the bone is blown away, leaving a gaping wound from which brain-matter may protrude.
Fig. 87. Diagrammatic Illustration of the Three Forms of ‘Gutter’ Fracture. (For further description, see text.)