Visual angle. (Opt.) See under Angle. — Visual cone (Persp.), a cone
whose vertex is at the point of sight, or the eye. — Visual plane, any
plane passing through the point of sight. — Visual point, the point at
which the visual rays unite; the position of the eye. — Visual purple
(Physiol.), a photochemical substance, of a purplish red color,
contained in the retina of human eyes and in the eyes of most animals.
It is quickly bleached by light, passing through the colors, red,
orange, and yellow, and then disappearing. Also called rhodopsin, and
vision purple. See Optography. — Visual ray, a line from the eye, or
point of sight. — Visual white (Physiol.), the final product in the
action of light on visual purple. It is reconverted into visual purple
by the regenerating action of the choroidal epithelium. — Visual yellow
(Physiol.), a product intermediate between visual purple and visual
white, formed in the photochemical action of light on visual purple.
Vis"u*al*ize (?), v. t. To make visual, or visible; to see in fancy.
[Written also visualise.]
No one who has not seen them [glaciers] can possibly visualize them.
Lubbock.
Vi*taille (?), n. [See Victuals.] Food; victuals. [Obs.] Piers Plowman.
Chaucer.
Vi"tal (?), a. [F., fr. L. vitalis, fr. vita life; akin to vivere to
live. See Vivid.] 1. Belonging or relating to life, either animal or
vegetable; as, vital energies; vital functions; vital actions.
2. Contributing to life; necessary to, or supporting, life; as, vital
blood.
Do the heavens afford him vital food?
Spenser.
And vital virtue infused, and vital warmth.
Milton.
3. Containing life; living. "Spirits that live throughout, vital in
every part." Milton.