pupifera (pupifera)

pl. [NL. (Lichten 1. The orifice of the iris; the hole or opening in the iris through which light pa es. The pupil appears usually as a black spot in the middle of the colored part of the eye, this appearance being due to the darkne of the back of the eye. The pupil contracts when the retina is stimulated, as by light, on accommodation for near distances and on convergence of the visual axes; pain may cause a dilatation. The size of the pupil is determined by the circular and radiating muscular fibers of the iris. It may also be influenced by drugs; thus, opium contracts and belladonna dilates the pupil. The same consequences may result from disease or injury. The shape of the pupil in most animals is circular, as the ex pre ion of the uniform action of the contractile fibers of the iris; but in many animals it is oval, elliptical, or slitlike. Thus, the pupil of the cat contracts to a mere chink in the sunlight, and dilates to a circle in the dark. The pupil of the horse is a broad, nearly parallel-sided fi ure obtusely founded at each endable he variability of the pupil in size is le remarkable in owls than in cats, but in these birds it keeps its circular figure, changing in size from a mere point to a disk which leaves the iris a mere rim. The pupil sometimes gives zoological charac iris, 6, and cuts under eyel. ters, as in distinguishing foxes from wolves or dogs. See 2. In zool.: (a) The central dark part of an ocellated spot. See ocellus, 4. (b) A dark, apparently interior, spot seen in the compound eyes of certain insects, and changing in position as it is viewed from different sides.-Argyll-Robertson pupil, a pupil which does not contract from light, but does with accommodation for short distances. It is a frequent symptom in locomotor ataxia.Exclusion of the pupil. See exclusion. Occlusion of the pupil, the filling up of the pupil with inflammatory material. Pinhole pupil, the pupil when so contracted, as it sometimes is, as to resemble a pinhole. pupilabilitył (pū"pi-la-bil'i-ti), n. [ What can he mean by the lambent pupilability of slow, low, dry chat, five notes below the natural tone? Sterne, Tristram Shandy, iv. 1.