De praecipius visus symptomatis eorumque causis Physica & Medica contemplatio

XXXV.
But it must be known that the ton chromaton emphaseis appearances of colors are established as ayles immaterial and of a kind ambiguous between bodies and incorporeal things, nor do they fulfill the role of accidents in every way, because they are separated from the subject without an alteration of the subject, since no quality leaves its accustomed seat silently and stealthily without some mark of change.

XXXVI.
Hence the other hypothesis flowed, namely, that vision occurs from contact kata dynamin by power/faculty and not kat' ogkon by bulk/mass, as pleased Empedocles. For a most thin and subtle species is carried into the eye, which strikes the sense by a certain hidden power without the affection of heat, cold, etc.

XXXVII.
Therefore, physicists, in order to express the reason for this otherwise most obscure business more correctly, borrowed a Type from the opticians, by which they demonstrate: that vision occurs through a pyramid, the base of which is on the body of the object, while the cone is in the center of the eye, with the perpendicular axis intersecting the angle of incidence, under which a distinct image is represented.

XXXVIII.
Although the optical hypothesis may seem more subtle than the physicist's institution, and for that reason was rejected by the recent Peripatetics, it would have been better to have applied a subtle reason of discipline to a subtle matter, than to have abandoned the consideration of art and nature out of blind pertinacity. Thus, indeed, many other theorems established by them are highly necessary for the explanation of vision, such as these:

XXXIX.
A visible body must be placed diametrically opposite to the sight. Also: Distinct vision occurs along perpendicular lines. Also: A visible body is not perceived by the eyes unless it has a logou proportion/ratio of quantity with the surface of the sight. Also: Vision is not completed unless the form received on the surface of the crystalline lens penetrates to the innermost nerve. Also: No visible body is seen equally as a whole at the same time. Also: Only the surfaces of object bodies are comprehended by the use of sight.

XL.
Opticians differ more acutely on the mode of reception, namely that the axis of the pyramid...