The spontaneous cessation of hæmorrhage is rather to be ascribed to the special method of production and the consequent nature of the wound. The lesions were the result of immense force strictly localised in its application, which might well induce very complete and rapid contraction of the vessel wall; while the track in the soft parts was not only narrow, but also lined by a thin layer of tissue possibly so devitalised superficially as to specially favour rapid coagulation of the blood. Beyond this the tracks were often sinuous when the position of the limb at the time of reception of the injury was replaced by one of rest. The influence of mere narrowness of the track is illustrated by classical experience in the development of aneurismal varices after stabs by knives or bayonets; and in the injuries under consideration the frequent development of large interstitial hæmorrhages into the tissues of the limbs indicated that blood does not readily travel along the wound track. It was noteworthy that when hæmorrhage did occur it was most free from, or often limited to, the wound of exit. This is due to the direction of the active current set up by the rush of the bullet through the tissues. The mechanical factor is, no doubt, the most important.
Control of primary hæmorrhage from a wounded vessel by the impaction of a foreign body was of much less frequent occurrence than appears to have been the case with the older bullets. I saw a case in which, on removal of a fragment of shell (Mr. S. W. F. Richardson), very free hæmorrhage occurred from a wound of one of the circumflex arteries of the thigh, but not a single one in which a similar result followed the extraction of a bullet of small calibre. The comparative infrequency of retention of modern bullets is probably one of the main elements in this relation. A very curious instance of provisional plugging of a wound in the upper part of the brachial artery by an inserted loop of the musculo-spiral nerve was related to me by Mr. Clinton Dent. This instance must, I think, be regarded as an accident definitely dependent on the size and outline of the bullet and on the nature of the force transmitted by it to neighbouring structures.
While, however, deaths from external primary hæmorrhage were rare, a considerable number resulted from primary internal hæmorrhage. In some of these, injury to the largest trunks in the thorax or abdomen led to an immediately fatal issue; in others wounds of the large visceral arteries, as of the lungs, liver, or mesentery, were scarcely less rapid in their results. In such cases the potential space offered by the peritoneal or pleural cavities favours the ready escape of blood from the wounded vessel, while the tendency of the blood effused into serous cavities to rapid coagulation is notably slight. Beyond this the comparative deficiency in direct support afforded by surrounding structures to vessels running in the large body cavities is also an important element in their behaviour when wounded.
These remarks receive support from the observation that few, if any, patients survived an injury to the external iliac vessels within the abdomen, while the remarkable instances of escape from fatal hæmorrhage from large vessels recorded below (cases 1-19) indicate that the mere size of a wounded vessel is not to be regarded as the sole factor in prognosis.
Recurrent hæmorrhage was occasionally met with both in the case of the limb and trunk vessels. In the limbs it often necessitated ligature of the artery. I saw several cases in the lower extremity where recurrent hæmorrhage on the second or third day was treated by ligature of the femoral or popliteal artery, and it also occurred during the course of development of one of the carotid aneurisms recounted below. On two occasions I saw rapid death follow recurrent abdominal hæmorrhage; in one I was standing in a tent when a man who had been wounded the day before suddenly exclaimed: 'Why, I am going to die after all.' The appearance of the man was ghastly, and on examining the abdomen it was found greatly distended, and with dulness in the flanks; the patient expired a few minutes later. Another example of recurrent abdominal hæmorrhage is related in case 169, p. 432.
Secondary hæmorrhage.—In simple wounds of the soft parts by small-calibre bullets this was decidedly rare. In wounds complicated by fractures of the bones, especially when they exhibited the so-called 'explosive' character, secondary hæmorrhage was not uncommon, and this not necessarily in conjunction with infection and suppuration.
In the chapter on fracture some remarks will be found on the prolongation of healing often observed in the exit portion of the wound track, which is explained by the well-known fact that, given an aseptic condition of the wound, sloughs of tissue separate very slowly. Secondary hæmorrhage in these cases is due to lesions of the vessel short of perforation, but severe enough to so lower the vitality that local gangrene of the wall occurs. In such instances hæmorrhage most usually occurred on the tenth to the fourteenth day, but occasionally still later. In one instance of ligature of the anterior tibial artery for such hæmorrhage three-quarters of the whole lumen of the vessel had been devitalised. The resemblance of some cases of secondary hæmorrhage of this class to those occasionally observed after amputation, and due to accidental non-perforative injury of the artery at the time of operation above the point of ligature, was very striking.
In other cases secondary hæmorrhage was the result of perforation of the vessel by a sharp spicule of bone, but in the large majority sepsis and suppuration were the cause. Naturally therefore the accident was commoner in the more severe kinds of wound, and in those caused by large bullets or fragments of shell. The symptoms in nearly all cases were the classical ones of repeated small hæmorrhages followed by a sudden copious gush.
The forms of secondary hæmorrhage, however, which afforded most interest were the interstitial and the internal, mainly on account of the scope they allowed for diagnosis.
Characteristic examples of internal secondary hæmorrhage are furnished by cases of chest injury accompanied by hæmothorax and fully dealt with under that heading (Chapter X.). Cases of interstitial secondary hæmorrhage are also described under the heading of traumatic aneurism and abdominal injuries (No. 194, p. 445). It therefore suffices here merely to remark on the diagnostic difficulties the condition gave rise to. These mainly depended upon the elevation of general bodily temperature by which the hæmorrhage was often accompanied. Further evidence of the condition was furnished by the development of local swellings, or physical signs indicative of the collection of fluid in a serous cavity. These signs developed rapidly, and the rise of temperature was sudden and decided enough to suggest commencing suppuration. In several cases incisions were made under the supposition that this had already occurred.