pupil


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pupil:

see eyeeye,
organ of vision and light perception. In humans the eye is of the camera type, with an iris diaphragm and variable focusing, or accommodation. Other types of eye are the simple eye, found in many invertebrates, and the compound eye, found in insects and many other
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.

Pupil

 

the opening in the iris through which light rays enter the eye.

The dimensions of the pupil change according to the amount of light present: the pupil dilates in darkness, under emotional excitement and painful sensations, or with the injection of atropine or adrenalin into the body; it contracts in bright light. Change in the dimensions of the pupil is regulated by fibers of the autonomic nervous system and is accomplished by means of two smooth muscles located in the iris—the sphincter, which contracts the pupil, and the dilator, which expands it. In higher vertebrates, changes in the dimensions of the pupil are produced reflexively by the effect of light on the retina of the eye; in lower vertebrates, these changes are produced by the direct action of light on contrac-tile formations in the pupil. The pupil is usually round or slitlike; in some fish (for example, in a number of sharks, rays, and flounder) and mammals (for example, in sperm whales and dolphins) a projection of the iris, suspended from the superior edge of the pupil, can cover the pupil completely in the presence of intense illumination. In man the pupil is round; its diameter may change from 1.1 mm to 8 mm. Changes in the shape, dimensions, and speed of reaction of the pupil (so-called pupillary reflexes) are of diagnostic significance in eye diseases.

O. G. STROEVA

pupil

[′pyü·pəl]
(anatomy)
The contractile opening in the iris of the vertebrate eye.

pupil

1
1. a student who is taught by a teacher, esp a young student
2. Civil and Scots law a boy under 14 or a girl under 12 who is in the care of a guardian

pupil

2
the dark circular aperture at the centre of the iris of the eye, through which light enters
References in classic literature ?
His professorship had been given up, and he had no pupils except Georgie Sanders and Mabel Hubbard.
Ere long I had acquired as much facility in speaking French as set me at my ease with my pupils; and as I had encountered them on a right footing at the very beginning, and continued tenaciously to retain the advantage I had early gained, they never attempted mutiny, which circumstance, all who are in any degree acquainted with the ongoings of Belgian schools, and who know the relation in which professors and pupils too frequently stand towards each other in those establishments, will consider an important and uncommon one.
As nothing escapes the piercing eyes of malice, Mademoiselle Thirion became, as it were, a sharer in the sudden emotion of master and pupil.
I had to run after my pupils to catch them, to carry or drag them to the table, and often forcibly to hold them there till the lesson was done.
When the arithmetic came, the little teacher was surprised to find her scholar quicker in some things than herself, for Phebe had worked away at the columns in the butcher's and baker's books till she could add so quickly and correctly that Rose was amazed, and felt that in this branch the pupil would soon excel the teacher if she kept on at the same pace.
Sambo in the carriage, together with a very small and weather-beaten old cow's- skin trunk with Miss Sharp's card neatly nailed upon it, which was delivered by Sambo with a grin, and packed by the coachman with a corresponding sneer--the hour for parting came; and the grief of that moment was considerably lessened by the admirable discourse which Miss Pinkerton addressed to her pupil.
Then he fell to dumbly playing, without striking the notes, while his little pupil was taken to an open window for air, and was otherwise petted and restored.
Not a day passed, in that dangerous intimacy of teacher and pupil, in which my hand was not close to Miss Fairlie's; my cheek, as we bent together over her sketch-book, almost touching hers.
Miss Peecher's favourite pupil, who assisted her in her little household, was in attendance with a can of water to replenish her little watering-pot, and sufficiently divined the state of Miss Peecher's affections to feel it necessary that she herself should love young Charley Hexam.
The first professor I saw, was in a very large room, with forty pupils about him.
The eyes were bestial, yellow-green, the pupils dilating and narrowing with sharp swiftness as they sought about among the lights and glooms of the room.
Being naturally great mimics of men's actions, they showed themselves most apt pupils, and when arrayed in their rich clothes and masks, they danced as well as any of the courtiers.