On sight, and its relation to inverted images / by Wm. Munro.

  • Munro, William.
Date:
[1858]
Catalogue details

Licence: Public Domain Mark

Credit: On sight, and its relation to inverted images / by Wm. Munro. 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.

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    m ON^SIGHT, )0 m ITS RELATION TO INVEllTED IMAGrl^^^ By Wm. MUNEO, M.D., M.E.O.S.L^p-^^^ jdnd iofe/y of Her Majesty's 83rd c& 93rd Highlanders. P' - fS-Si^^til^^^J Tlie advances made in the knowledge of optics, in the last a^Wd ^.^-.^ the present, and clnefly the discoveries of Sir Isaac Newton,^<igf V, ' .•nor, not to philosophy only, but to human nature. Such discove- '^s ought for ever to put to shame the ignoble attempts of our odern sceptics, to depreciate the liuman understanding, and to ^spirit men in the search of truth, by representing the human unities as fit for nothing but to lead us into absurdities, and contra- ,t;tions.—Reid on the mind. As the object of the following paper is to show how erect images le produced, and as its subject cannot fail to be extensively criticised • the most enlightened of the general public, and by many of the ost learned of my medical brethren ; little of the anatomy of the e need be recapitulated here, so as to make the subject as concise id simple as possible. It is known to every well-informed person that the ej^e of man d quadrupeds, though differing in some points, are formed upon le same dioptric principles, and with the same objects in view, viz: act as a system of lenses to convey light and outward luminous iipressions (through these) to the brain. To simplify the matter as much as possible, it would be better to ivte before proceeding further that I receive as axioms in the future . :marks, 1st. That rays proceeding from a rarer to a denser medium ' ■ e drawn towards the perpendicular. 2nd. Vice versa to the first, md 3rd. That the denser the medium may be, the sooner will the ys be brought to the perpendicular. Thus rays proceeding from any outer body in the air, on arriving d passing through the aqueous humour, crystaline lens, and treous humour, as they are all of greater densities than the atmoa- leric air are drawn to the perpendicular. By a peculiar construction about the eye of man and of quadrupeds can be made more or less convex, and thus adapted to greater or is distances. The i^resence also of a movable diaphragm, regulates e admission of light, and by these two properties it will become parent, on a little consideration that the object painted o» the terior surface of the retina may become larger or smaller. In the ■rmal condition of the organ, such does actually take place, as can sily be seen on exposing the eye to a dimmer or brighter light, ot as we go down the scale of animated creation, we find no such ntrivances, still we see a simpler but no less admirable ad(iptatiou means to an end. It has all along been a bugbear and stumbling block to philoso- lers why an inverted image (as seemed to them) should be depicted the retina, and thus convoyed to the brain, and which they