Observations on the nature and theory of vision : with an inquiry into the cause of the single appearance of objects seen by both eyes / by John Crisp, F.R.S.
- Crisp, John
- Date:
- MDCCXCVI [1796]
Licence: Public Domain Mark
Credit: Observations on the nature and theory of vision : with an inquiry into the cause of the single appearance of objects seen by both eyes / by John Crisp, F.R.S. Source: Wellcome Collection.
Provider: This material has been provided by the Francis A. Countway Library of Medicine, through the Medical Heritage Library. The original may be consulted at the Francis A. Countway Library of Medicine, Harvard Medical School.
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![[ 9^ the definition of the optic axis which Dr, V/clls has laid down. If the termination of this axis on the retina is not precifely the center, f!:ii] I conceive that the law of vifible direction mentioned by Dr. Smith and by Dr. Reid, will not be afFecled by fuch trifling deviation from ilrid: geometrical pre- cifion. It is a fa(9:, that points whofe pro- jecPcions on the retina are the terminations of thefe axes, appear united ; and the quefiion I mean to confider is, Whether this apparent union is the caufe of fome law of viiible dj'redion from the eye ? or, Whether it refults from fome original property independent of any fuch law of vilible direction ? founded on experiments made on the eyes of dead animals, the precife form thus determined cannot, I think, be depended upon. However, it feeras an acknowledged fad:, that there are certain points of one retina which correfpond with certain points of the other; infomuch, that the objecls projected on thefe points refpectively appear united: the correfpondence of the points I conceive is founded on this property of producing a fingle appearance, and not a ftri6i; geometrical limilarity. I PER-](https://iiif.wellcomecollection.org/image/b21175408_0113.jp2/full/800%2C/0/default.jpg)
