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 ?
Master and pupil understood each other, and Ginevra no longer feared to ask:--
The baffled pupil returned for the bag, expressing surprise at her carelessness; but this act of Servin's was to her fresh proof of the existence of a mystery, the importance of which was evident.
When your pupil was a little innocent child, did she ever amuse herself by building a house of cards?"
Perhaps you would prefer talking to me about these two pupils of yours?
From this deficiency of nourishment resulted an abuse, which pressed hardly on the younger pupils: whenever the famished great girls had an opportunity, they would coax or menace the little ones out of their portion.
"I must be responsible for the circumstance, sir," replied Miss Temple: "the breakfast was so ill prepared that the pupils could not possibly eat it; and I dared not allow them to remain fasting till dinner-time."
The pupil had been, in her state of pupilage, so imbued with the class-custom of stretching out an arm, as if to hail a cab or omnibus, whenever she found she had an observation on hand to offer to Miss Peecher, that she often did it in their domestic relations; and she did it now.
After his death, Miss Ladd had taken Netherwoods (as the place was called), finding her own house insufficient for the accommodation of the increasing number of her pupils. A lease was granted to her on moderate terms.
Only when her pupils quitted the establishment, or when they were about to be married, and once, when poor Miss Birch died of the scarlet fever, was Miss Pinkerton known to write personally to the parents of her pupils; and it was Jemima's opinion that if anything could console Mrs.
I descended to the schoolroom with no remarkable eagerness to join my pupils, though not without some feeling of curiosity respecting what a further acquaintance would reveal.
The accidents of conversation; the simple habits which regulated even such a little thing as the position of our places at table; the play of Miss Halcombe's ever-ready raillery, always directed against my anxiety as teacher, while it sparkled over her enthusiasm as pupil; the harmless expression of poor Mrs.
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.