SPECIES I. DINUS VERTIGO. Vertigo. DIZZINESS, WITH A FEAR OF FALLING. GEN. V. Pathological hitherto un COMMON as this complaint is, I have not hitherto met with any satisfactory explanation of its cause. Sauvages*, indeed, has entered upon the subject pretty fully, as has Darwin + since his time, and Crichton since the time of Darwin; while on the continent it has been investigated with much patience and ingenuity by Dr. Herz of Berlin §. For the most part it has been ascribed to a morbid excitement, or increased action in the organ of vision, which is the view taken of it by Sauvages and Darwin, or Sauvages. to" a state of mental confusion arising from too rapid a succession of representations", which is the explanation of Herz and Crichton. Darwin. Herz. That there is, in all instances, some degree of mental Crichton. confusion, may, perhaps, be allowed, and that there is often too rapid a succession of representations with a morbid increase of sensorial action, may be allowed as readily: but if the following remarks be found entitled to attention, and succeed in delineating the real nature of vertigo, it will appear that the external senses are only indirectly, if at all, the seat of the morbid action: that the energy of these is far more frequently in a state of diseased diminution than of diseased increase; and that even a rapid succession of representations is not essential to the sensation. † Zoonom. Class IV. 11. i. 10. * Nosol. Method. Class VIII. Vesaniæ. GEN. V. SPEC. I. Dinus We have had frequent occasions of showing that the nervous power which supplies the muscular fibres is communicated, not strictly speaking, in a continous tenour, but in minute and successive jets, so that the course of New view of this delicate fluid is alternately broken and renewed by a In a state series of fine and imperceptible oscillations. Vertigo. Vertigo. the subject. Irritative power how communi irritable fibres. of health and vigour this succession of influx and pause is cated to the perfectly regular and uniform, and hence, whatever movements result from it will partake of the same uniformity, and appear to be one continued line of action instead of a successive series. But as soon as ever the harmonious alternation through which the nervous power is thus supplied, is interfered with, the oscillations become manifest; the apparently uniform current is converted into a tremulous undulation, and the muscular exertion to which it gives rise, instead of being seemingly one and undivided, is sensibly multiplied into hundreds of which any person may convince himself on observing a strong and healthy arm extended for a few minutes with a small weight at the end of the fingers, and an arm reduced in strength by a fever, or any previous labour; for while the first maintains an even and uniform line, in the second this line is broken into perpetual tremors and undulations. All other nervous fibres supplied in a That the nervous power which supplies the muscular fibres is communicated in this way there is no doubt; and, as it is highly probable that all the different kinds of nervous fibres are fed by a like process; there can be little doubt, also, that those which maintain an intercourse bein the line of tween the brain and the external senses, and even those similar way: and subject to similar disturbances communi cation. From this want of uniform action in the flow of the sentient which belong to the external senses themselves are supplied by the same kind of alternating pause and flow. And consequently that, as a perfect regularity and uniformity in this alternation is the means of conveying from the organ of vision to the sensorium one undivided perception of every single object presented to it, so, an irregularity and want of uniformity in the alternating series, must confuse and complicate the perceptions, and multitiply them into as many as the series of jets themselves consist of, though each perception may, perhaps, be less GEN. V. SPEC. I. Dinus Vertigo. distinct and perfect than the single perception conveyed in the ordinary course. Thus, in looking through a window, or an eye-glass, the objects that pass before us in regular order, pass singly and without confusion; but if this order be interrupted by movements we are not ac- fusion and customed to, or the objects jerked about, as in a magic complication lanthorn, they make us dizzy with their motion, and we tations. see them confusedly and in delusive numbers. power a con of represen Hence veraction of the tigo a clonic nervous servient to perception. fibres sub Principle applied to the phænomena of vertigo. Why objects In this manner, then, it appears to me that the increased motion, and apparently rapid succession of representations, is produced in the affection we call vertigo: which, under this explanation, is a clonic action of the nervous fibres subservient to perception, in the same manner as the rapid and tumultuous agitation of the muscles in tremor, shaking palsy, or epilepsy, are a clonic action of the fibres subservient to voluntary motion. In the last of these affections we find a considerable difference in the nature and intervals of the clonic movements; for these must depend upon the greater or less degree of interruption, which the nervous power sustains in its flow, or upon the peculiarly relaxed or spastic state of the nervous fibres themselves, and probably, at times, upon some other cause of which we are totally ignorant. And we have, hence, reason to expect, and do in fact perceive, an equal diversity in the clonic and illusory motions of ver- circumtigo; for the objects or their representations presented to volve, the perception appear sometimes to circumvolve horizontally from right to left, or perpendicularly from above downwards, or from below upwards, or to be very whimsically changed in their form. And not unfrequently the why the patient patient himself seems to be moving as well; and com- himself. monly in a contrary direction to the apparent motion of the objects. And as the intermediate nerves between the other external senses and the brain seem occasionally to coincide in the same morbid agitation, we can easily conceive how that very common modification of the disease may be produced in which the dizziness is combined with illusory sounds, as of whispering or murmuring, the ringing of bells, or beating of drums, or even the roar of appear to GEN. V. SPEC. I. Dinus Vertigo. Vertigo. Whence illusory sounds, and multiplication of objects. Whence illusory smells and tastes. Vertigo often present whether there be light or darkness: hence not from increased energy in the irritative mo organs of cannon: for, as single objects may, under the influence we are now contemplating, be prodigiously multiplied or magnified, so may single, and otherwise almost imperceptible sounds; and especially where the auditory nerve is itself in a state of high morbid acuteness, during which we have already had occasion to remark that the gentlest and lightest tones, even the whisperings of a mere current of air in a room, or the breathing of persons present, is intolerable, while sounds before unperceived become highly distressing *. And in like manner by an equal irregularity in the flow of the nervous fluids subservient to the perceptions of smell and taste, we may account for similar illusions upon these faculties. In many instances, we find the vertigo equally present whether the patient be in the dark or light, whether the eyes be closed or open; and we have hence a full proof that it is not dependent, as Dr. Darwin conceives, upon an increased energy in the irritative motions of the organs of vision. In some cases the representations of objects are very numerous and rapid, but in others far less so, and particularly where the affection is severe from the tions of the first, or the patient is in a state of constitutional debility; under which circumstances we may conceive the pauses in the flow of the nervous fluid to be more irregular or of longer duration than they otherwise would be.. In many cases, indeed, the only sensation is that of a buoyant undulation or swimming without any succession of representations whatever; affording us a proof that the rapid succession of representations described by Dr. Herz, is not more essential to vertigo than the increased energy of as supposed Dr. Darwin. by Herz. vision, as conceived by Darwin. Objects not always re presented as frequently rapid or successive or increased in number But as the disease advances, or, in other words, as the flow or secretion of the nervous fluid becomes still more interrupted, the representations are confused, indistinct, and rapid in succession, often conjoined with a sense of dimness or darkness, existing equally whether the eyes be shut or open, forming a state by Hippocrates and the * See Paracusis acris, Vol. III. Cl. IV. Ord. II. Gen. 11. Spec. 1. GEN. V. SPEC. I. Dinus Greek writers generally called scotoma or scotodinus : and as the disease makes a further progress by a further interruption in the flow of the sensorial fluid, every power Vertigo. Vertigo. of body and mind augments in languor, till at length sen- Scotoma sation both external and internal fails altogether, the ac- and scototion of the heart, and the other involuntary organs is en- dinus what. Swooning feebled, and the patient swoons away, or sinks into a often an fainting fit, constituting the morbid condition we shall effect, and have to describe under the next genus. why. Predispo nent cause of vertigo nervous de- Who chiefly subject to these affec The great predisponent cause in all these cases, whether of muscular agitation or of vertigo, is nervous debility or exhaustion: the exciting causes are whatever has a tendency to disturb the uniformity with which the nervous power is supplied through the whole of its fibres, and from exhaustion. one fibre to another. And hence those persons are most subject to both kinds of affection whose nervous system is constitutionally weak and mobile, or has become debiliatated by disease or accident. Hence dyspeptic patients are peculiarly subject to both these affections; as are those who are faint from sudden and violent evacuations, want tions. of food, or a long course of labour. Hence we meet with it as a frequent and distressing attendant upon those who have too freely indulged in the pleasures of the table, in those of sexual intercourse, and particularly the gross gratification of self-pollution. And hence, too, we may see why it is so often an accompaniment of cephalæa, as the nervous fibres subservient to the organs of perception are here influenced from contiguous, in some cases from continuous, sympathy. causes: The exciting causes we have stated to be whatever has Exciting a tendency to disturb the uniformity with which the nervous power is supplied through the whole line of its fibres. Of these the chief are motion or exertion to which the chiefly of strength is not equal; motion to which the system has not been accustomed, or hurried motion whether external or internal. In a state of great weakness, whether from hunger, hard labour, hemorrhage, or a protracted fever, even the ordinary motion of gentle walking is more than the little three kinds. First kind, exertion to which the motion or strength is not equal. |