III. Glancing or oblique perforating wounds of varying depth in any portion of the cranium.—These injuries were the most common, the most highly characteristic of small-calibre bullet wounds, the most interesting from the point of view of diagnosis, prognosis, and treatment, and beyond this they formed the variety most unlike any that we meet with in civil practice.
They were met with in every region of the cranium, and in every degree of depth and severity. The lesser are best designated as gutter fractures, the deeper are perforating and gradually approximate themselves to the type of injury described as class 1.
When the bullet struck a prominent or angular spot on the skull a considerable oval-shaped fragment was occasionally carried away, leaving an exposed surface of the diploë (case 60, p. 274). Under these circumstances the apparent lesion on raising a flap was slight, but exploration often showed extensive intra-cranial mischief. Thus in the case referred to both dura and brain were wounded, and continuing hæmorrhage led to the development of progressive paralysis, relieved only by operation.
From the more deeply passing bullets a more or less oval opening resulted, in which both tables were freely comminuted and displaced. These cases differed from the typical gutter fracture only in length and outline, and the nature of the accompanying intra-cranial lesion was identical, while in the latter particular they differed much from fractures in which the impact of the bullet was direct, in spite of a near resemblance in the appearances in the osseous defect.
I saw one instance in which a circular fissure about 1½ inch from the actual opening of entry surrounded the latter, the area of bone within the circle being somewhat depressed, though radial fissures were absent.
In several of these cases fragments of lead were either found on the fractured surface of the bone or within the cranial cavity, showing that the bullets had undergone fissuring of the mantle, or had actually broken up on impact.
Gutter fractures.—The nature of the injury to the bones in these is best illustrated by a series of diagrams of sections such as are shown below.
Fig. 64.