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 PATHOLOGY 391 ting of a door, some occasional pains being felt where the external sapluenous nerve runs behind the outer ankle and over the outside of the heel. After a lapse of time there is an attack of sciatica, the first of a series continuing for years, in which the course of the diffusive pain can be tracked, as if it had had an anatomical know ledge of the nerves of the limb, along all the branches of the great sciatic nerve to the thigh, leg, and foot. In this case the sequence of events is the same as in the former : the original excitant had touched the terminal twigs of the external saphsenous branch of the great sciatic nerve ; after an interval intense neuralgic pain begins to be felt far up the great nerve-trunk itself ; and the pain diffuses itself not only to the filaments belonging to the external saphrenous branch but along all the branches. A limited peri pheral disturbance has, after an interval, become central and diffusive, and the pain apt to recur intermittently for years after. tanus. Let us now take a case of tetanus involving the very same peri pheral nerve as the last case. A boy engaged on a farm chafes the outer side of one heel by wearing boots too large for his feet ; the abrasion, which is exactly over the course of the external sapluenous nerve, is disregarded, and the irritation of the boot permitted to continue. In a few days he is admitted into hospital with tetanus, that is to say, with the neck -muscles rigid, the jaw locked, the features drawn, the recumbent body bent forwards from time to time like a bow, its whole weight resting on the head and heels, occasional wild jerkings of the limbs, and the muscles everywhere as hard as boards. This horrible and painful state of the muscular system usually ends in the patient dying after a week or ten days or less, exhausted by hunger and thirst and want of sleep, or by inability to breathe under the vice-like grip in which the chest is held by the muscles of respiration. The sequence of events is here closely parallel with that in the cases of neuralgia : an irritated condition of a small outlying nerve -twig, which is not a motor nerve, has, after a short interval, touched the spinal cord in such a manner that motor force is freely and continuously let loose over the whole muscular system, with occasional discharges of a more intense kind. Spasm commencing in the muscles near the injury has been spoken to by the patients or attendants sometimes ; but the observation has been recorded, on the whole, seldom. Strangely enough, it is in the muscles of the face, neck, and throat that the tetanic rigidity shows itself first, in whatever part of the body the injured nerve may be. There probably always is an injured nerve somewhere, although it is necessary to admit a few cases of &quot; idio- pathic &quot; tetanus in which the nerve-injury is unknown. Gunshot- wounds of nerves are most likely to be followed by tetanus, as well as lacerated, contused, and punctured wounds generally, including the bites inflicted by canine teeth. The tetanic onset may follow the wound immediately, or it may come on while the wound is &quot; cleaning &quot; or suppurating, or during the stage of scarring, or some time after the cicatrix has formed. A wound which has been neglected in the healing, in which foreign particles have been left, or in which the nerve has been involved in the tightening of the scar is most apt to be followed by tetanus. A certain temperament, or state of the mind and body, predisposes to it ; the frequency of tetanus in war may be due to more than one cause, but it seems necessary to include among the predisposing factors the excitement or preoccupation of the battlefield. Certain states of climate predispose to it ; in the dry Australian air it is not uncommon for wounds to be followed by tetanus, and the disease is equally common within the tropics, especially under the circumstances which ordinarily cause chill. Among animals the horse is particularly liable to it, especially as a sequel of castration. The rise of temperature in tetanus is probably the effect of the excessive muscular metabolism. is- Explosive Discharges of Nerve -force on slight Provocation. mrges Instances of neuralgia and of tetanus as the sequel of a peripheral
 * nerve- injury, or series of scarcely observed excitations, are illustrations

rce. of that remarkable property of the nervous system which Rind- fleisch speaks of as involving a &quot;disproportion between cause and effect.&quot; The central nervous system, he says, &quot;has a capacity for absorbing enormous quantities of centripetal or ingoing excitations as if they left no trace ; but in reality it stores them up in the form of potential energy. It is this that enables an impression which may hardly exceed the limits of physiological excitation, but is aided in various ways by circumstances, such as inherited feeble ness, lowered nutrition, or blood-poisoning, suddenly to let loose the whole store of these accumulated forces and to give rise to an outbreak of the most acute feelings and the most powerful move ments.&quot; The want of outlet at the time is an error that underlies much of nervous disease, both purely psychical and other. The brooding upon wrongs, real or imagined, the unsatisfied hunger for sympathy, pent-up or unexpressed emotion under many cir cumstances, even the solitude of shepherds on the Australian and New Zealand downs, are among the causes tending to a total un hinging of the mind. Such illustrations of the general principle are beyond the scope of this article ; the illustrations that concern us most at present are found rather in the province of reflex nervous activity, where the response is automatic, not always recorded by the consciousness, and little if at all controlled by the will. Some disorders in this group are purely functional, that is to say, there are no concurrent structural changes. In others, the functional disorder is attended or closely followed by degeneration ; and these are mostly diseases of the spinal cord. Representative instances from each of these two classes will now be adverted to briefly. Convulsions (Eclampsia). Apart from the convulsions of ursemie Convul- poisoning, there are two prominent divisions of eclampsia the sions. convulsions of infancy and childhood and the convulsions of the pregnant or puerperal state. In infancy the reflex movements and uncontrolled spontaneities are predominant, just as the impressions from the outer world are but little discriminated or retained. It takes little to throw some infants into a fit ; the irritation of teething, of ill-digested food, of worms, and the like will suffice. Whether in these cases the excitations have been accumulating or not, the discharge of outgoing energy is always explosive. The muscles that straighten the back are contracted to the utmost, and the air is forcibly expelled from the chest with a prolonged cry ; the head is thrown back, and the arms and legs kept rigid. The state of rigid spasm (tonic contraction) is succeeded by rapid con tractions and relaxations (clonic) of the muscles of the face and limbs and whole body, which gradually become more comprehensive in sweep and slower in rhythm until they cease. Consciousness has meanwhile been suspended, and does not return until some ten or twenty minutes after the convulsive movements have ceased ; with the return of consciousness the patient &quot; comes out of the fit.&quot; The liability to such attacks diminishes very strikingly as the intelligence and the will develop and the body hardens. It is not until the circumstances of pregnancy and childbed arise that any liability to convulsions at all comparable to that of infancy is again met with. No analysis of the circumstances of puerperal convulsions can be attempted here ; if they are in some cases of &quot; unemic &quot; origin, in association with the albuminuria of pregnancy, there are other cases that are primarily disorders of reflex inner- vation. Epilepsy. An epileptic fit does not differ materially in its pheno- Epilepsy. mena from a fit of convulsions as above described ; the tongue is more apt to be caught between the teeth in the rapid movements of the lower-jaw muscles, and the spectacle of a grown person in a fit is more distressing in every way. That which really distin guishes epilepsy from eclampsia is that it is a habit of the nervous system, with a good deal of regularity in its recurrences. Fits of convulsions in infancy will cease when the cause is removed, when teething is over, or worms expelled, or after the probationary state of the nervous system has been outgrown. The convulsions of childbed also, if the patient happily survive the attack, come to an end when the critical state of the system has passed. But it is the distinctive mark of epilepsy that it tends to become an ingrained habit, that the fit is there in jwssc, as if detached from its exciting cause, established, permanent, and self-existent on the paths of ingoing and outgoing nerve-influence. This tendency of a disordered reflex action to repeat itself is the same &quot;memory&quot; that has been claimed by Hering for the cells and mechanisms of the body generally. That which is implied in the original use of the word, namely, retentiveness or the resurrection of past im pressions, and the contagion of associated ideas, is a mystery large enough to cover the minor mystery of morbid habit. Epilepsy is, as it were, the self-existent memory of a disordered reflex ; and this is what we may understand by the term &quot;neurosis.&quot; It is true that a primary disorder of reflex action due to an adequate cause, such as infantile or puerperal convulsions are, cannot be always shown to have occurred at one time or another in epileptics. In a certain proportion of cases there has been an injury to the skull, or there are evidences of tumour or other new formation within the skull, or there is a tumour of a peripheral nerve, or a nerve involved in the scar of a wound or sore ; but there are many more epileptics in whom such antecedents cannot be made out. The habit, in fact, is one which tends to be ingrained not only in the individual who has begun it but also in his or her family. Epilepsy is one of the clearest instances of a liability transmissible from parent to off spring. The heredity of epilepsy has even been proved by Brown - Sequard for the guinea-pig ; when an epileptic habit was induced in guinea-pigs by injuring the spinal cord or the medulla oblongata, or by cutting the sciatic nerves, the litters of such epileptic guinea- pigs were apt to have epileptic seizures, attributable to nothing but inherited liability. According to Hasse s figures, epilepsy has begun before the age of twenty in by far the larger number of cases, and that fact is doubtless an index of the extent of hereditary influence. If we do not assign all such cases to heredity, the advent of puberty in girls may be held to be itself a cause of epi lepsy ; that time of life is distinguished by the somewhat abrupt acquisition of a much wider emotional and intellectual range, and presumably by some special liability to explosions of reflex nerve- force upon slight provocation. Ckorca(St Virus s Dance). This is another variety of uncontrolled St movement which is also a habit, like epilepsy, and is practically Vitus s confined to girlhood and boyhood. It may occur in pregnant dance.