pupil (2)

[Fr. pupille, from Lat. pupilla a little girl, the pupil of the eye; Sp. pupil a; Port. & Ital. pupilla.] Anat.: The circular opening of the iris (q. v.). Its direction is slightly to the nasal side of the iris; its contractions are caused by the circular layer of the iris, and dilation by the radiating fibers of the anterior or muscular layer. "When you shut one eye, the pupil of the other, that is open, dilateth."- Bacon : Nat . Hist ., § 868. Pin - hole pupil : Pathol.: The pupil of the eye when so contracted that it is suggestive of a pin-hole.