CONCUSSION of the spinal cord had already been an object of study before the present war era, but authors were only able to devote themselves to a description of the anatomical and clinical manifestations following on direct blows to the vertebral column or on falls from a height. Experimentally it was also possible to observe the lesions produced by successive blows on the vertebrae. We may recall the studies which had already established the existence from the clinical and anatomical point of

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... view of concussion of the nervous centres, notably of the cord, because we wish to limit this account to the description of functional disorders and alterations in the cord which occur in those who have been subjected to gunshot injury, but in whom the cord has not been directly damaged by the missile. We L are speaking here of traumatisms due to the bursting of shells near the patient, or of wounds produced by projectiles which have not struck the cord itself. ' J I. Concussion of the cord may be'divided into two categories: (a) Indirect concussion, resulting from the bursting close to the patient of large shells, and in which the symptoms are caused by sudden variation of pressure. (b) Direct concussion, produced by the impact on the vertebral column or at a certain distance from it, of various projectiles (bullets, I shell splinters, &c.), but in which the cord and its membranes I have not been damaged by the missile. Such is the distinct tion which we have endeavoured to make in our previous work on this question. In both cases the spinal lesions are associated with the agitation of the nervous centres which have not been directly injured by the missile. (<x) Indirect conoussion.-Indirect concussion includes those cases in which spinal paralysis occurs as a result of the explosion of projectiles of large calibre, and in which it is impossible to find any external wound as the explanation. From the beginning of the war these facts arrested the attention of medical officers; they have been attributed to i the action from a distance on the central nervous system of i the "wind from the bullet," but it is necessary to subject i these observations to a critical and careful study in order to I discriminate between disorders of organic origin and those of a psycho-neuropathio nature. In France the cases of Sencert, of Ravaut,2 of Guillain,3 of Heitz, of Babinski,5 of P. Marie and Chatelain have put beyond a doubt the existence of motor and sensory disturbances due to organic lesions of the cord in patients showing no evidence of any wound, but who were within the range of an exploding shell. A. Léri has collected most of these facts in a critical study. Functional disorder may supervene immediately after the explosion. The patient is unable to use his limbs, he has the impression that they have been carried away, whilst at the same time he often complains of severe pain in the back. Sometimes disorders at first little noticed become accentuated some hours later. On the other hand, in some cases paralyses, which before had been general, are seen to lessen and to become limited to certain limbs (Lhermitte 8). A. Léri has insisted lately on the presence of " delayed" " concussion, in which several days and sometimes even weeks after the explosion the first important gross symptoms of organic lesion have made their appearance. The spinal syndrome following concussion due to explosion generally assumes the aspect of a quadriplegia or a paraplegia caused by transverse myelitis. The paralysis is accompanied by changes in the tendon reflexes, by disturbances of sensation, weakness of the sphincters, and trophic phenomena (bed-sores), such as are found in organic spinal lesions. But it should be borne in mind that there may be partial paralysis, anaesthesia, of abnormal distribution, and retained reflexes which make the diagnosis doubtful, at least at first, because the hypothesis of simple functional disease is not easy to eliminate. The organic signs then only develop slowly. Such are certain muscular atrophies indicating an alteration in the grey matter of the cord, and giving, on electrical examination, the reaction of degeneration. These amyotrophies, moreover, tend to improve. The evolution of these paraplegias or partial paralyses occurring after concussion varies according to the extent and gravity of the lesions. Relaxation of symptoms or their transformation into others is fairly common. For example, paralysis, flaccid at first, tends to become spasmodic. Nevertheless, the prognosis often continues quite favourable. A fatal termination, however, may occur either during the early hours or days as the result of shock, or later from pulmonary complications or various infections. It is difficult to follow completely the history of indirect spinal concussion caused by explosion, because the morbid anatomy, and, above all, the histology of the lesion has not yet been investigated. Lumbar puncture, it is true, has shown in some cases the presence of haemorrhage into the cerebro-spinal fluid or the remains of hemorrhage (albuminose, xanthochromia), which has induced certain authors to deduce that spinal lesions are probably hsemorrhagic in type. There is no doubt that hsemorrhagic foci are present in many cases, but at the same time we cannot exclude the view of Roussy and Lhermitte,lO who hold that in a certain number of cases the nervous agitation caused by the deflagration has produced a direct traumatism of the vertebral column, and that the spinal concussion will therefore be of the same nature as the second category of spinal lesions, to which we have given the name of direct concussion. The following has been urged in support of the hypothesis. The concussed man is often thrown to the ground, blown up, bruised, or buried, so that the role of agitation is not easy to distinguish from that of direct injury. Moreover, even when a single explosion can be shown to be the cause it occurs in the most typical cases behind the patient, who gathers the impression of having received a blow on his back or loins (Leri). There would thus be produced a sort ' of blow on the vertebral column, and we know as a fact that in these patients ecchymoses do occur in the limbs and certain other parts of the body exposed to the deflagration, which, acting like a blow, causes haemoptysis, haematuria, and the like. It is possible that the same may hold good in concussion, or that the blow caused by the explosion is superadded to the phenomena which accompany atmospheric compression or decompression-factors often brought in to elucidate the pathogeny of concussion from explosion. Roussy and Lhermitte," from a study which they have made of these symptoms, have formulated a theory which brings the symptoms of indirect concussion into close association with those of direct concussion. The impact -violent and limited by the edges of the cone of compressed gas to the spine or paravertebral region-would be comparable to the impact of a projectile. In each case, the authors say, the impact is transmitted to the nervous or spinal elements by the cerebro-spinal fluid, the sole difference being that in direct concussion the immediate traumatic agent penetrates and bruises, whereas in concussion caused by pure explosion there is commotion and agitation only. It appears, then, that the study of direct concussion ou2;ht especially to give us interesting information, seeing that it appears to resume in a more general way the story of spinal concussion. II. (b) Di1'{}Ct eonous8'ion.-In our first study of direct spinal concussion (October, 1915) we demonstrated that the passage of war projectiles through the vertebral canal or its imme-