2. Certain Phenomena applied in Solution of Difficulties connected with the Theory of Vision

Extract

The theory of vision has been the subject of much more scientific study than that of any of our other senses, but notwithstanding this, the subject is still encumbered with some difficulties and contradictions, the solution of which is essential to our having a true and complete theory. Such are the questions,—first,—regarding single and double vision, as depending on the excitement of corresponding, or, as they are generally called, identical points of the retinæ; second,—the question whether perception is in the retinæ or in the brain; and lastly, the question regarding the decussation and ultimate course of the fibres of the optic nerves.