The Philosophy of Mystery

by Walter Cooper Dendy

These, then, are the remote sympathies with the organs of digestion; and this chiefly by the derangement of the circulation of the blood, between the brain and the heart.

In the case of an enlarged heart, Dr. Kelly discovered that a dark spectrum was perceived synchronous with the systole, or contraction of its ventricles; so that the patient could count his pulse merely by watching the motion of this illusive shade on the white ceiling of his room.

The study of these false perceptions, which result from derangement or disease of the eye, are replete with interest. You are aware that the function of a nerve of sensation is so deranged by disease, that in some cases of paralysis cold bodies will appear heated. So, by analogy, is the function of a nerve of sense deranged, if its fibrillæ be disordered.

We have Myopia, or short sight; Presbyopia, or long sight; Chrupsia, or coloured vision. We have night-blindness, or dim vision, and day-blindness, or intolerance of light,—as in the albino, or owl. I had, and I have now, a second relative, whose vision is insensible to certain colours; and the chemist, Dalton, we know, could not distinguish blue from pink.

In a Glasgow Medical Journal, I read this statement by a patient:—“No colour contrasts to me so forcibly with black as azure blue, and as you know that the shadows of all objects are composed of black, the forms or objects which have acquired more or less of this blue hue, from being distant, become defined and marked by the possession of shadows, which are invisible to me in the high-coloured objects in a foreground, and which are thus left comparatively confined and shapeless masses of colour.”

The eye may be curtailed of half its object. Mr. Abernethy and Dr. Wollaston were both often in this dilemma of a sense, so that only one-half of a person or a name, on which they were looking, was visible to them. Mr. Abernethy, in his facetious way, referring to his own name, told us he could see as far as the ne, but could not see a bit of the thy. This illusion is at once explained by anatomy. The optic nerve, at one point, interlaces some, and crosses other of its fibres: thus one nerve chiefly supplies one-half of both eyes. Disease of nerve may thus paralyse one-half of each retina: the other half only perceiving half the object or word.

In many cases of disordered sensibility of the retina, it is influenced by the minute villi or vessels in the tunics of the eye. In the case of exhausted energy of this retina, usually accompanied by night-blindness, where there is no vision but in a strong light, floating specks termed muscæ volitantes often become so numerous, as to impart a notion of films floating in the watery humour of the eye, or before the cornea. It is a curious question, in what portion of the retina the spectra of muscæ volitantes are excited. They appear in or near the axis of vision; but as they do not interrupt the visual rays from material objects, it is possible they may arise on that spot considered to be destitute of vision, with regard to external impression. Or they may be produced by detached parts only of the objects, which impinge on the retina, reaching the brain. If the integrity of certain of its fibres, which by converging form the optic nerve, be destroyed, distorted or imperfect objects will be presented. This speck may be a musca volitans.

Astr. The original impressions in all cases are, I presume, from without: how is the internally excited idea presented as a prominent image before the eye?

Ev. That form of disordered vision to which I allude, occurring so often in nervous persons, or resulting from close application to study, does not often appear to depend on a turgid condition of the vessels of the choroïd coat or retina. It is usually relieved more by tonics than by depletion; and very strange illusions of sight will sometimes be produced merely by depressing medicines, especially the preparations of antimony. Yet these dark specks appear to be floating before, and often at some distance withoutside the eye. Therefore we may believe that excited images or more perfect forms may also appear before the retina, palpable. Between the first impression and its recurrence, a long period may have passed (memory being unlimited); and it is sufficient that one sole idea be excited to produce a succession; as a spark of fire will ignite a train of gunpowder; or as an electric spark will discharge a whole battery.

In the curious case of photopsia, or suffusio scintillans, we have a series of illusive spectra, in the forms of “lucid points,” and “yellow flames,” and “fiery veils,” and “rings of light.” In some cases of ophthalmia, and in acute inflammation of the brain, the candles and other bright objects in the chamber will look like blood. Beguelin, as we read in the “Berlin Memoirs,” by straining his eyes on a book, always saw the letters red.