De praecipius visus symptomatis eorumque causis Physica & Medica contemplatio

IX.
Anaklasis reflection is the reflection of a visible species from a smooth, polished, and solid body into the opposite sight, along a straight line.

X.
Diaklasis refraction is the bending of the line of incidence, which they also indicate as the extension of the form, occurring in different transparent bodies placed between the eye and the object.

XI.
Furthermore, the subject of vision is the instrument of the eye, complete in all its parts, and specifically the Crystallinus humor crystalline lens/humor within it, suffused and illuminated by the animal spirit, in which, according to Aristotle, as in a certain kato'ptroi empsychoi ensouled mirror, a representation of external images occurs: this humor is splendid by its nature and solid, so that it exists as a certain fluid thickening of condensed light, apt for the impression of the species.

XII.
The spirit of the opsis faculty of sight flows abundantly from the brain into the eye through the optic nerves.

XIII.
Although the origin of the animal spirit is one, by which the functions of all the senses are administered, it is nonetheless likely that in its distribution, not only a peculiar dynamis power/faculty is added, but also a change or alteration of substance, which, if you please, we may name idiokrasia individual temperament/idiosyncrasy, added in proportion to each part, so that the analogy between cause and effect remains settled within its own bounds, which the mutual comparison of the senses clearly shows.

XIIII.
Indeed, the visible species is the most subtle of all others that are perceived by hearing, taste, smell, or touch, for which reason it also requires a sensorium similarly equipped with an equal faculty, so that the same proportion that exists between objects may also be established in the organs of the senses. Hence it will become manifest that the optic spirit excels in its subtlety and light by as many degrees as the interval by which the emphasis appearance/reflection of colors surpasses the affection of hot, cold, moist, or dry.

Catchword: "Ratis" (raft/ship)