starting from the skin of the neck or from other parts of the body, are as certainly related to the muscles whose contraction constitutes a convulsion as are any physical or physiological effects that have been hitherto described.* In this altered central nutrition, therefore, we recognise the peculiar organic condition upon which convulsion depends; and we see, further, that it may be immediately produced by an impression from without. The evidence on the latter point is derived partly from experimental inquiry and partly from clinical observation. Experiment has shown that the primary fact in convulsions is a peculiar condition of some portion of the nervous centres, which may be induced artificially ;† and clinical observation has shown that convulsions may arise from eccentric irritation, and be cured by the removal of the latter. In such circumstances, therefore, the only conclusion we are warranted in forming is that the organic condition of convulsions was the direct result of the irritation. There is no further difficulty in accounting for the operation of eccentric causes; for, if an irritation is capable of originating convulsive conditions without pre-existing proclivity to their occurrence, à fortiori, is it capable of so doing when that proclivity exists. The mode in which prolonged irritation operates is, although explicable upon the foregoing principles, further elucidated by other considerations. A certain degree of stimulation is necessary to produce a certain motor effect. This is to be observed in regard of all reflex operations, from the contraction of the iris in proportion to the amount of light, to the contraction of the muscles of the leg in proportion to the irritation of the skin, in paraplegia. But further, certain reflex actions in health appear to be occasioned only after, not the increase in amount of intensity of the impressing cause, but after prolongation or repetition of that cause; for example, respiratory movements, uterine contractions, and emissio seminis. And again, the experiments of M. Brown-Séquard show that time is required for the establishment of the convulsive conditions even * Researches of M. Brown-Séquard on Epilepsy. in those animals in which they are brought about by lesion of the spinal cord. The term "irritation" has been used in the preceding paragraphs because it is one the general meaning of which is readily understood, but it must be freed from certain possibilities of misinterpretation. It is not to be thought that this kind of irritation bears any definite or constant relation to pain. On the contrary, it is most frequently observed that the irritants which induce convulsion are accompanied by little suffering; and further, that the individuals in whom convulsions occur, from such eccentric causes, often bear very severe pain without such results. Thus, an individual in whom convulsions are the frequent result of painless indigestion, may have a tooth extracted without suffering a fit; and the child whose attacks have been caused by dentition, the distress from which is only evinced by occasional fretting, may feel so much pain at the lancing of its gums as to scream violently, and yet no paroxysm follows. Again, the irritation is not necessarily even accompanied by sensation. In M. Brown-Séquard's artificially induced epilepsy of the guinea-pig, mere contact, or blowing on the surface of a certain portion of the neck, was sufficient to induce attacks; whereas the most violent irritation of the leg which was in a state of hyperæsthesia was not followed by the paroxysm. M. Brown-Séquard argues, and with conclusiveness, that "fits are caused by a peculiar and unfelt kind of irritation;" and that this may or may not co-exist with the feeling of pain, cramp, formication, &c. * The eccentric irritation may be due to some foreign body brought in contact with the afferent nerves, such as ascarides, indigesta, &c., or it may be the result of disease originating in any part of the body. C. The particular organic condition upon which convulsions depend, may be part of a systemic or general disease, or morbid tendency. In such cases the nervous centres are involved with other organs and tissues in a general nutrition-change. To this category belong cases of convulsion associated with, * Researches on Epilepsy, p. 6. † P. 31. and apparently having for their cause, such general cachexia as tuberculosis, scrofulosis, rachitis, and syphilis; such morbid blood-conditions as urinæmia, anæmia, pyæmia, and other toxæmiæ, arising from changes occurring within the system; such blood-diseases as alcoholism, lead-poisoning, typhus, variola, and other exanthemata; such profound general modifications of nutrition as accompany the progress of disease in certain important organs, e. g. pneumonia, carditis, pericarditis; and lastly, such as attend certain developmental periods,-for example, puberty, pregnancy, dentition, and the like. When convulsions occur in a well-marked instance of any one of the cachexia, it may be that they are primary, or idiopathic; it may be that they are secondary or dependent on eccentric irritation; and further, they may be symptomatic, or produced by the irritation of the nervous centres, as in tubercular meningitis. But over and above these three modes of production, there are numerous cases which require another explanation: viz. this, that the convulsions are the direct expression of the cachexia which is present; the nervous centres being involved in that general nutrition-change which is the essential element of the cachexia itself. That which is common to these general disturbances of nutrition, is an increase in the molecular changes of the tissues, accompanied it may be by an increase of material, the latter often assuming a form which is foreign to the organism. Virchow describes as the third form of general nutrition disturbance, "der Theil nimmt ueberschuessiges Material auf; die Bewegung steigert sich (progressive Metamorphose), und zwar (a) in der Richtung des alten Gewebes (Hypertrophie, Hyperplasie), (b) in einer fremden Richtung (Heterotrophie, Heteroplasie).' The occurrence of an increased molecular movement in an organ or tissue is commonly associated with an augmentation of its vital function; so that whereas on the part of a secreting organ such abnormal increase will occasion a greater quantity of secretion, a similar excess on the part of an organ of innervation will give rise to pain, spasm, or delirium. "Handbuch der speciellen Pathologie und Therapie, Erster Band," p. 273. Conf. " 'Allgemeine Störungen der Ernährung," p. 271, and "Allgemeine Formen der Störung," pp. 15 et seq. In regard of the toxæmiæ, doubtless a frequent mode of causation of convulsions is the direct action of a certain poison upon the nervous centres. Thus, Frerichs has shown that carbonate of ammonia, resulting from the decomposition of urea in the blood, exerts an action which may be imitated by its artificial injection.* But the forms of disturbance in the nervous centres of urinæmic patients vary widely, and it seems probable, as Dr. Walshe suggested, that more than one poison may be developed from the decomposition of urea in the blood. But whether there are several or only one, their mode of action must be by inducing that nutritionchange upon which convulsions depend. Allowing, however, that the nutrition may be thus affected through a distinct agency in the blood, this agency being the product of a local disease, we cannot by such means explain every case. For the existence of poisons has not yet been demonstrated, but only inferred, in other toxæmiæ. That which is definitely ascertained is that there is a profound change in the general nutrition; and this exhibits itself in the functions of almost every organ, producing altered secretions, oppressed or painful sensations, deficient power, and exaggerated motility. The nervous centres in such conditions partake of the general change; and while in some cases rigors, cramps, jactitations, subsultus tendinum, vertigo, delirium, and stupor, may be the only phenomena which are presented, in others sudden loss of consciousness and violent convulsions may ensue. With regard to those diseases which result from the introduction of poisons foreign to the organism, similar remarks apply. In fever convulsions arise in the same manner as headache, oppression, rigors, heat of skin, and foul secretions; viz., by the profound alteration of nutrition; and the same is true, probably, of chronic alcoholism, and lead poisoning. But in acute poisoning it may be that the particular agents employed, -opium, and some narcotic irritants, for example,-exert a specific influence upon the nutrition of the nervous centres, the latter being disturbed independently of any general assimilative change. 278. "Die Bright'sche Nierenkrankheit, und deren Behandlung," pp. 107 and In a similar manner we must interpret the occurrence of convulsions in pneumonia and pericarditis. It certainly is not found that convulsions bear any constant proportion to the amount or intensity of pain which local diseases may occasion. Nothing can exceed the suffering sometimes caused by lumbago, pleurodynia, the passing of biliary or renal calculi, the onset of pleuritis; but such affections rarely exhibit the complication of convulsions: while the pain of pneumonia, or of pericarditis may be extremely trivial, and yet this complication shall occur. On the other hand, it is quite certain that the lastnamed diseases are frequently the expression of a previously existing morbid nutrition, and are almost invariably attended by profound changes in the assimilative power of the whole organism. The conclusion, therefore, is obvious, that, besides operating as eccentric irritants, diseases of particular organs have the power of occasioning convulsions, in proportion to the degree in which they effect or express a general nutritionchange; and the inference is, I think, warranted that the mode in which convulsion is brought about is by the involution of the nervous centres in this general condition. The mode in which dentition, puberty, &c., operate, is more fully discussed in regard of epilepsy. (See Chap. V., Pathology.) D. The particular organic condition upon which convulsions depend may be originated by more or less contiguous structural disease. Thus, an intracranial tumour, a chronic inflammatory condition of the meninges, a process of softening and disintegration of the brain substance, or any other structural change in the nervous centres or their appendages, may set up that peculiar interstitial or molecular change which is the immediate cause of convulsion. 66 The structural diseases which are found in association with convulsions are not the immediate, but the remote causes of the latter. They act by inducing those interstitial changes which are the proximate cause;"* and it is because this relation has been misunderstood, that so much confusion has existed in cerebral pathology. * Liverpool Medico-Chir. Journal, Jan. 1, 1858, p. 9. |