In a milit&ry sense the scalp wound is the most important of head injuries, since it eventually produces the least disability. If -disablement does follow it is due to deeper injury, either from penetration of the calvarium and dura or from cerebral contusion. But the development of sepsis in otherwise uncomplicated cases prevents rapid return to work. This has been the case in countries other than our own. Thus Briesen in a review of over five thousand head injuries in Los Angeles remarks that

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... the longest periods of hospitalization were caused by septic scalp wounds. There is another important factor-that an infected scalp wound makes it impossible to undertake such exploratory punctures of the skull and dura as the later progress of the case may demand. Probably only those with considerable knowledge of head injuries realize how important a factor this is. The risk applies not only to airraid casualties but also to road accidents, especially those of motor-cycle dispatch riders, to which Cairns (1941) in particular has paid attention. While we do not wish to overemphasize the dangers of scalp wounds, or to present the view that only a handful of men know how to treat them, we believe that some guidance will not be taken amiss by those with less experience of these cases. Mechanism of Injury A survey of a large number of casualties from several bombed cities indicated that roughly 25% of all patients admitted to hospital suffered from injury to the head, and 75% of these had scalp wounds of some sort. From their number scalp wounds became a problem of importance. The reason for the frequency of head injuries lies in the fact that so many air-raid casualties were caused by the collapse of a dwelling-house. Injuries in the open, in works, or in shelters were much rarer. The common story was that the patient was sitting in the kitchen or downstairs room when the house was shaken down by a near miss. The fact that the details of the injury were generally unknown to the patient was due to the traumatic amnesia that indicated concussion, and to the rapidity, if not the unexpectedness, of events. The scalp wound of the airraid casualty looks as if finely ground brick, cement, and dirt had been blasted into the exposed tissues by a jet of compressed air. Ingrained in the margins of the scalp, embedded in the periosteum and in the muscle, is commonly a fine layer of this particulate matter. Most of the multiple injuries were due to flying glass; there might be 10 to 50 or more small wounds on the neck, face, and scalp. Eye injuries were frequent, sometimes with penetration of the globe; more often there was conjunctivitis caused by blast-driven grit. Many of the patients had been buried, and appeared worse than they really were. Cleansing, washing, and shaving the head presented not a few technical difficulties to the uninitiated. Bomb fragments themselves rarely caused the injuries: most scalp wounds, apart from those due to flying glass, resulted from the crushing of the scalp between the bone and falling debris, or from the ground if the patient was blown over-that is to say, many of the head injuries produced by air raids were caused by blunt types of violence. The scalp was squeezed until it gave way, when lateral movements might have come into play. These wounds were often irregular in shape, with contused edges. It was a characteristic that they were severely grimed: rrortar, plaster, and brick dust were rubbed in at the time of impact, or found their way in as the patient lay imprisoned in a heap of. rubble. As a generalization it can be asserted that these wounds were much more contaminated than the ordinary accidental scalp wound of peacetime; further, that the force which produced them was much greater. It was not rare to find the pericranium ingrained with dirt, whilst it had often been so severely ground against the bone that a whole area of scalp might be torn away or pulverized out of existence. Most scalp wounds penetrate into the areolar layer between the galea and pericranium, tailing off more superficially at the extremities of the wound. The crushing nature of the injuring force may be recognized in the contused state of the wound margins, the irregular shape of the object by a stellate or pleomorphous pattern. A tearing movement may be added by the sliding of the scalp so that a flap is fashioned; side tracks off the main traject are produced by sliding or by a broad surface of impact. Difficulties in excision may be introduced by the presence of horizontal slits in the scalp parallel to the skull contour. These are due to variable stresses in the layers of the scalp. The complicated nature of some of these wounds, particularly when tissue has been lost, calls for judgment and technical skill. Deep Injury in Scalp Wounds It has been said that penetration of the head by metallic fragments did not prove to be as common as preconceptions forecast. Window glass was a commoner mnissile, but was usually stopped by the calvarium. This barrier cannot be relied upon, and more than one patient had glass penetration as deep as the hypothalamus. Quite apart from penetration by flying fragments, cerebral contusion was not rare. Intradural contusion was evidenced by the frequency of the amnesia that betokens concussion, while routine lumbar punctures revealed the presence of blood in the cerebrospinal fluid in some 20% of apparently pure scalp wounds. McKissock and Brownscombe (1941) have had a similar experience in their series of scalp wounds. At the close -of the last war one of us described the neurological signs presented by patients hit by high-velocity missiles, a point unrecognized by other observers save one (Hine, 1918). Monoplegias, sensory and visual disturbances, and Jacksonian fits were all observed. It was anxiety on this score that caused the institution of the somewhat ill-received instruction to notify scalp wounds. But there was another reason-the fact that penetration of the skull was too often being overlooked and that these wounds were not being treated with the foresight vhich their nature demanded. 4251