The human sensorium : investigated as to figure by a course of pressures on the eyes, and by the induced phases and bearings of those sensations of colors called peacock's feathers : being a second supplement to the Rationale of cerebral vision / by John Fearn.

  • Fearn, John, 1768-1837.
Date:
[1832]
Catalogue details

Licence: Public Domain Mark

Credit: The human sensorium : investigated as to figure by a course of pressures on the eyes, and by the induced phases and bearings of those sensations of colors called peacock's feathers : being a second supplement to the Rationale of cerebral vision / by John Fearn. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

    22/40 (page 22)
    to bo contradicted by proof, tliat the Sentient subject is merely a flat surface, without depth. 4. Having- put the subject to the test by pressure on a sin</le eye; we may next proceed to that of a still higher criterion, by calling both eyes into action. With this in- tent, if we press simultaneously upon the outer angle of each eye; and carry the pressures round the eyes, nearly on their Equators; we shall see two Peacock's Feathers, each travelling in a circle, and maintaining its situation in exact opposition to the point of its own pressure. And here, the most remarkable new phenomenon for our consi- deration is that, instead of the two feathers travelling throughout in one same circle, or orbit, as happens when we press on two opposite sides of the Equator of a single eye, each of the Feathers, in a great part of its course, ex- hibits an exclusive orbit of its own, but which intersects, though it does not throughout coincide with, that of the other. The place to enlarge upon this last consideration is farther on. In this place, it is enough to say that the phenomena, taken together, put us in possession of the fact that the Sensorial Region is, in gross, common to impres- sions from both eyes; but, that it is extended laterally, on each side, to a field which cannot be reached by impres- sions from the farther eye, as shown in the Plate.—It fol- lows, from this experiment, that the Sensorial Region, as far as it is revealed in these results, is not strictly of the figure of the eye, or spherical; but is extended laterally, very considerably more than it is vertically, and so far appears to be of a spheroidal figure. The disposition of the two eyes which reveals this figure is evidently contrived, or at least is such in fact, as serves for the useful end of enlarging the horizontal field of our vision; which, I shall hereafter shew, is far greater than is at all supposed by Optical Writers: While its utility for our information, and preservation, is evidently great; though it does not strike our ordinary notice.