A rationale of the laws of cerebral vision : comprising the laws of single and of erect vision, deduced upon the principles of dioptrics / by John Fearn.

  • Fearn, John, 1768-1837.
Date:
[1830]
Catalogue details

Licence: Public Domain Mark

Credit: A rationale of the laws of cerebral vision : comprising the laws of single and of erect vision, deduced upon the principles of dioptrics / by John Fearn. Source: Wellcome Collection.

Provider: This material has been provided by UCL Library Services. The original may be consulted at UCL (University College London)

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    pair of scissors, that theJield, or image, which we see on the RIGHT hand, and which is occasioned by a retinal image in the left eye; and that field, or image, which we see on the left hand, which is occasioned by a retinal image in the right eye; are re-crossedy or at least newly produced, visual images in the mind, in consequence of the previous retinal impressions. To sum up this very extraordinary history; I have now to add that, when we press upon the open eyes; we can not only see both the peacock's feathers, but, with difficulty, we can gain sight also of our nose, with each eye. And herein we contemplate the most preposterous phenomenon that can well be imagined : For, while we now see the right side of our nose with our right eye, as we should expect it to appear; we see it stand on the LEFT side of the left side of our nose as seen with the left eye:—In other words ; in our pre- sent field of vision, with both eyes, we see two images of a side of our nose, the one image prepos- terously toward the other; and the image that stands on the left, is that seen by the right eye; while that which stands on the right is that seen by the left eye ; insomuch that, we behold at the same time two noses obliquely point to point. Among the other consequences of this strange exhibition ; it is certain that, as each of the seen images is seen in consequence of a retinal image which falls with the utmost possible obliquity on the retina, we have herein a final confirmation of the fact that Dr. Potterfield's Principle of Perpendicu- larity is utterly void of foundation in nature. It remains therefore to repeat here, that the two