2. That can be seen; visible. [R.]
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.
4. Being the seat of life; being that on which life depends; mortal.
The dart flew on, and pierced a vital part.Pope.
5. Very necessary; highly important; essential.
A competence is vital to content.Young.
6. Capable of living; in a state to live; viable. [R.]
Pythagoras and Hippocrates . . . affirm the birth of the seventh month to be vital.Sir T. Browne. Vital air, oxygen gas; so called because essential to animal life. [Obs.] Vital capacity (Physiol.),
the breathing capacity of the lungs; expressed by the number of cubic inches of air which can
be forcibly exhaled after a full inspiration. Vital force. (Biol.) See under Force. The vital forces,
according to Cope, are nerve force growth force and thought force all under the direction and control
of the vital principle. Apart from the phenomena of consciousness, vital actions no longer need to be
considered as of a mysterious and unfathomable character, nor vital force as anything other than a form
of physical energy derived from, and convertible into, other well-known forces of nature. Vital functions
(Physiol.), those functions or actions of the body on which life is directly dependent, as the circulation
of the blood, digestion, etc. Vital principle, an immaterial force, to which the functions peculiar to
living beings are ascribed. Vital statistics, statistics respecting the duration of life, and the circumstances
affecting its duration. Vital tripod. (Physiol.) See under Tripod. Vital vessels (Bot.), a name
for latex tubes, now disused. See Latex.