The direction of the tracks obviously depends on the attitude assumed by the patient at the moment of impact of the bullet and the direction whence the firing has proceeded. The frequent assumption of the prone position during the campaign led to the occurrence of a large proportion of longitudinal tracks in the trunk, or trunk and head, which will be referred to later. Certain battles were in fact strongly characterised by the nature of the wounds sustained by the men. Thus at Belmont and Graspan, where some rapid advances were made in the erect attitude, fractured thighs were proportionately numerous, while at Modder River, where many of the men lay for a great part of the day in the prone position, glancing wounds of the uplifted head, of the occipital region, or longitudinal tracks in the trunk and limbs were particularly frequent. I very much regret that the material at my disposal does not allow me to add some remarks as to variation in the nature of the wounds according to whether they were received from an enemy firing from a height or from below, but it is possible that some information on this subject may be forthcoming when the returns of the Service are made up, since it is naturally of great importance as to the effect of trajectory in the proportionate occurrence of hits.
3. Multiple character of the wounds.—The same conditions responsible for the length and directness of the tracks, account for the frequently multiple character of the wounds implicating either the limbs or viscera—thus, lung, stomach, liver; neck, thorax, abdomen; abdomen, pelvis, thigh. Also for the frequent infliction of two or more separate tracks by the same bullet—thus, arm and forearm with the elbow in the flexed position; both lower extremities; both lower extremities, penis or scrotum; leg, thigh, and abdomen, with a flexed knee; upper extremity and trunk, and more rarely one upper and one lower extremity. Again, it was remarkable how often the same bullet would inflict injuries on two or more separate men, not unfrequently dealing lightly with the first and inflicting a fatal injury on the second, or vice versâ. The small calibre of the bullet, moreover, allows of the neatest and most exact multiple injuries. Thus in a patient who was crawling up a kopje on all fours, the flexed middle digit of the hand was struck. The bullet entered at the base of the nail, first emerged at the distal interphalangeal flexor fold, re-entered the metacarpo-phalangeal fold, and finally emerged from the back of the hand between the third and fourth metacarpal bones.
4. Small 'bore' of the tracks, and tendency of the injury to be localised to individual structures of importance.—Here we meet with the most striking characteristic of the injuries, and evidence that reduction of calibre affects more strongly the nature of the lesion than does any other element in the structure of the modern rifle. The diameter of the track slightly exceeds that of the external apertures, probably as a result of the more ready separability of the elements of the structures perforated than exists in the skin. The calibre, moreover, tends to be fairly even throughout when soft structures only are implicated, though local enlargements result wherever increased resistance is met with. Thus a strong fascia may offer such resistance as to increase locally the bore of the track, and in this particular the state of tension of the fascia when struck will affect the degree of the enlargement. The most striking instances of local enlargement of the track are of course seen when a bone lies in the course of the bullet, but we must here bear in mind the introduction of a new element—the propulsion of comminuted fragments together with the bullet itself. In cases of fracture the distal portion of the track is in consequence many times larger than the proximal. The most striking examples of small even tracks are seen, on the other hand, in punctures of the elastic and practically homogeneous lung tissue, where the wounds are extremely small.
On transverse section of the track the gross amount of actual tissue destruction occupies a lesser area than that corresponding to the diameter of the bullet. The destructive action of the projectile is in fact exerted mainly on the tissues directly lying in its course, the track being opened up during the rush of the passage of the bullet, partly as a result of its wedge-like shape and partly as a result of the throwing off of the tissues forming the walls of the track by a diversion of a portion of the force in the form of spiral vibrations dependent on the revolution of the bullet. Again, the opening out of the tissues may be aided by the direction taken by the first and strongest as well as the simplest series of vibrations transmitted, which would assume the shape of a cone of which the point of impact forms the apex.
The escape from actual destruction by structures lying in the immediate neighbourhood of the track is indeed often surprising, but not perhaps so astonishing as the perforation of long narrow structures such as the peripheral nerves and vessels, without irreparable damage to the parts remaining, and this although the structures themselves may be of a diameter not exceeding that of the bullet itself. The capacity of these projectiles to split such structures as tendons was already well known before our experience in this campaign, but the injuries to the nerves and vessels of the same character came as a surprise to most of us. The lateral displacement of tissues seems to bear a strong resemblance to what is seen on the passage of an express train, when solid bodies of considerable weight are displaced by the draught created without ever coming into contact with the train itself. The tendency to lateral displacement is still more strongly exhibited when dense hard structures such as bone are implicated. Here the fragments at the actual points of impact on the proximal and distal surfaces of a shaft are driven forwards, while the lateral walls of the track in the bone are simply comminuted and pushed on one side without loss of continuity with their covering periosteum.
The extension of this form of displacement to a degree amounting to a so-called explosive character in the case of the soft tissues, even when the bullet passed at the highest degrees of velocity, was, however, never witnessed by me, and I very much doubt the existence of a so-called 'explosive zone' so far as wounds of the soft parts are concerned. On the contrary, I am inclined to believe that the highest degrees of velocity are favourable to clean-cut neat injuries of the soft tissues. I saw a large number of type wounds of entry and exit inflicted at a range of under fifty yards.
5. Clinical course of the wounds.—The tendency of simple wounds such as are above described to run an aseptic course was very marked, and, given satisfactory conditions, deep suppuration and cellulitis were distinctly rare. It may also be confidently affirmed that when suppuration did occur, with apertures of entry and exit of the normal small type, this was always the result of infection from the skin, or infection subsequent to the actual infliction of the wound. The infrequency of suppuration depended on the aseptic nature of the injury, the smallness of the openings, the small tendency of the track to weep and furnish serous discharge in any abundance, the comparative rarity of the inclusion of fragments of clothing or other foreign bodies, and possibly in some degree on the purity and dryness of the atmosphere, which favoured a firm dry clotting of the blood in the apertures of entry and exit, and consequent safe 'sealing of the wound.'
As to the aseptic nature of the injury, it will be well to first consider the question of the sterility of the bullet. Putting laboratory experiments on one side, the large experience of this campaign seems to prove to absolute demonstration that, bearing in mind the very large proportion of instances of primary union in simple tracks, the surgeon has nothing to fear on the part of the bullet itself. This is the more striking when we remember that these bullets shortly before their employment were carried in a dirty bandolier, and freely handled by men whose opportunities of rendering either their hands or implements aseptic were as bad as it is possible to conceive.
Several explanations are to hand, but none of them conclusive. Two must, however, be shortly considered. First, the surface of the bullet, except its tip and base, is practically renewed by passage through the barrel. Secondly, there is the question of the heat to which it is subjected. As far as cauterisation of the tissues is concerned, this question has been practically settled in the negative, since actual determinations of the heat immediately after the moment of impact have been made, and again it has been shown that butter is not melted, and that neither gunpowder nor dynamite is exploded, by firing bullets through small quantities of those materials. Again, the absence of any sign of scorching of the clothes of the wounded is strong evidence against the possibility of any considerable heat being applied to the tissues of the body; while another observation, although of less importance as affecting spent bullets only, that bullets, which have perforated the body but lie between the skin and the clothing, leave no sign of cauterising action on either, may be mentioned. None the less, the sources of heating while the bullet is passing from the barrel are many and obvious. Thus there is the heat consequent on explosion of the powder, the warm state of the barrel itself when the rifle has been fired a few times consecutively, and the heat resulting from the force and friction essential to the propulsion of the bullet through the barrel. Again, bullets covered with wax before their introduction into the barrel retain no trace of this when they have been fired, although at any rate the portion covering the tip is not exposed to friction on the part of the rifle, and lastly the base of the bullet has no other explicable reason for its innocuousness than subjection to a certain degree of heat. While not claiming any cauterising action on the tissues by the bullet, I should therefore still be inclined to allow the probability of the heat to which the surface of the bullet is exposed exerting a cleansing action on the projectile. In regard to this point it is interesting to bear in mind that shots from an ordinary gun seldom or never give rise to infection.
Foreign bodies were rarely carried into the wounds with the bullet. I saw several instances in which portions of the metal of cigarette cases and of cartridge cases when the bullet had perforated cartridges in the wounded man's bandolier, and in one instance small pieces of glass from a pocket mirror, must have been carried in without any obvious ill effect. Fragments of clothing, on the other hand, in every case caused suppuration: clothing was not often carried in, the khaki linen was perforated with a clean aperture, most commonly a slit; but the thick woollen kilts of the Highlanders, and thick flannel shirts, occasionally furnished fragments. The introduction of large pieces of clothing is a sure proof of irregularity of impact on the part of the bullet. The frequency with which portions of cloth were introduced from the kilt was one of the strongest surgical objections to its retention as a part of the uniform on active service.