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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![[ ^73 ] I MENTION this circumftance merely to remove any doubt of each eye being equally afFedled ; but our experiment requires the eyes to be clofed, when a fingie coloured fpot or fpedrum will become plainly perceptible. I requefl: the reader's particular attention to the circumftances of this experiment: the fpedlrum appears iingle, and no forced dif- tortion of either eye or of both at the fame time can affed: the unity of the appearance. But w^hat is this appearance ? it is merely a matter of fenfation, the central part of each eye is ftrongly affcdted by the late impreffion of the light on it. Here is no external objed: feen or imagined, and confequently nothing refpeding dirediion from the eye or external place can be concerned in this experiment! the whole relates to fenfation; but as each eye is equally afteded, the fenfation mull be united, otherwife the fpectra would ap- pear diftind:; we have not even a confci- oufnefs of both eyes being concerned, and tbe method above-mentipned is neceffary to • de-](https://iiif.wellcomecollection.org/image/b21175408_0195.jp2/full/800%2C/0/default.jpg)
