1. Extensive sagittal tracks passing deeply through the brain, and vertical wounds passing from base to vertex or vice versa, in the posterior two thirds of the skull. These will be referred to as general injuries.
2. Vertical or coronal wounds in the frontal region.
3. Glancing or obliquely perforating wounds of varying depth in any part of the head.
4. Fractures of the base.
Of these classes the first was nearly uniformly fatal; the second relatively favourable, and with low degrees of velocity often accompanied by surprisingly slight immediate effects; while the third had perhaps the best prognosis of all, but this varied as to the defects that might be left, and with the region of the head affected.
1. General injuries.—Fractures of this class may be treated of almost apart. For their production the retention of a considerable degree of velocity on the part of the bullet was always necessary, and the results were consequently both extensive and severe.
The aperture of entry was comparatively small, since to take so direct and lengthy a course through the skull the impact of the bullet needed to be at nearly an exact right angle to the surface of the bone. Any disposition to assume the oval form, therefore, depended mainly upon the degree of slope of the actual area of the skull implicated. In size the aperture of entry did not greatly exceed the calibre of the bullet; in outline it was seldom exactly circular, but rather roughly four-sided, with rounded angles, slightly oval, or pear-shaped. The margin of the opening consisted of outer table alone, the inner being always considerably comminuted. Fragments of the latter, together with the majority of those corresponding to the loss of substance of the outer table, were driven through the dura mater and embedded in the brain. These bony fragments were more or less widely distributed over an area of a square inch or more, and not confined to a narrow track.
Fig. 61.
Diagram of Aperture of Entry in Occipital Bone, showing radiating fissures exact length. The exit in the frontal region was of typical explosive character. Range '100 yards'