The characters of the external wounds will be first considered, followed by some remarks concerning the symptoms attendant on the different degrees and types of lesion, the symptoms special to injuries to different regions of the head, and on the subsequent complications observed.

In the simplest injuries the type forms of entry and exit wound were found, and it has already been observed that in these, if symmetrical, considerable difficulty existed in discriminating between the two apertures. This is to be explained by the fact that the arrangement and structure of the scalp are identical in corresponding regions; hence the only difference in the conditions of production of the entry and exit wounds exists in the absence of support to the skin in the latter. The granular structure of the hairy scalp is opposed to the occurrence of the slit forms of exit, hence the openings were usually irregularly rounded. Any increase of size in the exit wound in the soft parts due to the passage of bone fragments with the bullet, was equalised in that of entry by the fact that the latter, as supported by a hard substratum, was usually larger than those met with in situations where the skin covers soft parts alone.

In some cases of gutter fracture the wounds of entry were large and irregular, as a result of upward splintering of the bone at the distal margin of the aperture of entry in the skull, and consequent laceration of the scalp. Again, on the forehead very pure types of slit exit wound were often met with in the position of the vertical or horizontal creases. With higher degrees of velocity on the part of the bullet and consequent comminution at the aperture of exit in the bone, the scalp was more extensively lacerated, and large irregular openings in the soft parts, often occupied by fragments of bone and brain pulp, were met with. It is well to repeat here, however, that the presence of brain pulp in a wound by no means necessarily indicated the aperture of exit, for it was sometimes found in the entry opening also.

In the most severe cases, such as are included in class I., the exit wound often possessed in the highest degree the so-called 'explosive' character. From an opening in the skin with everted margins two or more inches in diameter a mass of brain débris, bone fragments and particles of dura-mater, skin, and hair, bound together by coagulated blood, protruded as a primary hernia cerebri if the patient survived the first few hours after the injury. In other cases of the same class the actual opening was smaller, but the whole scalp was swollen and œdematous, sometimes crackling when touched from the presence of extravasated blood in the cellular tissue, while firm palpation often gave the impression that the head consisted of a bag of bones over a considerable area.

Gutter fractures of the scalp were sometimes situated beneath an open furrow, gaping from loss of substance, or beneath a bridge of skin; in the latter case they were usually palpable. Simple punctures were also usually palpable, but the smallness of the openings sometimes rendered their detection more difficult than might be assumed.

I never saw a case in which the skull escaped injury when the bullet struck the scalp at right angles, but the frequency with which Mauser bullets were found within the helmets of men would suggest that this must have sometimes occurred. A case of injury to the external table alone has been described (p. 243). An illustration of the next degree of injury is afforded by the following:—A bullet lodged in the centre of the forehead, the point lying within the cranial cavity, while the base projected from the surface: this patient suffered but slight immediate trouble, so little, indeed, that he merely asked his officer to remove the bullet for him, as it was inconvenient. The bullet was subsequently removed in the Field hospital.

In a few cases the bullet entered the skull and was retained, when only a single wound was found. Such cases are described in Nos. 54 and 68, where the position of the bullet was determined by palpable fractures beneath the skin. With regard to the retention of bullets, however, in small-calibre wounds, it was always necessary to examine the other parts of the body with great care, and to ascertain, if possible, the direction from which the wound was received, as an exit was often found some distance down the neck or trunk. Again the possibility of the opening having been produced by glancing contact had to be considered.

In cases which survived the injury on the field, free hæmorrhage, as in wounds of other regions, was rare, and although general evidence of loss of blood was often noted in patients brought in, progressive bleeding was seldom observed. Again, when the wounds were explored, the amount of blood, although considerable, was usually not more than sufficed to fill up the space consequent on the loss of brain tissue. This was especially striking when large venous sinuses, as the superior longitudinal, were involved in the injury. None the less, hæmorrhage at the base of the brain was, I believe, responsible for early death in many of the severe cases, especially when the wounds were near the lower regions of the skull.

Escape of cerebro-spinal fluid was not so prominent a feature as might have been expected, considering how freely the arachnoid space was opened up in many cases. I think this was usually checked by early coagulation of the blood, and later by adhesions. It must be remembered also that extensive wounds were most common on the vertex, or at any rate over the convex surface of the brain, while fractures of the middle fossa were usually rapidly fatal.

Concussion.—Cases exhibiting symptoms of pure uncomplicated concussion were distinctly rare, as would be expected from the mechanism of the injuries. On the other hand, symptoms of concussion formed the dominant feature of all severe cases.