The frog: an introduction to anatomy, histology, and embryology . c covers about five-sixths of the eyeball:it is tough, white, and opaque. iii. The cornea, which covers the outer sixth of theeyeball, is circular, transparent, and continuous atits margin with the sclerotic: it is more convexthan the sclerotic. iv. The coi^junctiva is a delicate epithelial layer, con-tinuous with the skin, covering the front of thecornea and part of the sclerotic. V. The iris is the oval pigmented ring seen throughthe cornea. vi. The pupil is the central, oval, or dumb-bell shapedaperture surrounded by the iris
The frog: an introduction to anatomy, histology, and embryology . c covers about five-sixths of the eyeball:it is tough, white, and opaque. iii. The cornea, which covers the outer sixth of theeyeball, is circular, transparent, and continuous atits margin with the sclerotic: it is more convexthan the sclerotic. iv. The coi^junctiva is a delicate epithelial layer, con-tinuous with the skin, covering the front of thecornea and part of the sclerotic. V. The iris is the oval pigmented ring seen throughthe cornea. vi. The pupil is the central, oval, or dumb-bell shapedaperture surrounded by the iris. vii. The optic nerve is a thick white bundle of nervefibres piercing the sclerotic at the back of theeye. 2. Cut aU round the cornea, with stout scissors, about \ inch THE EYE 89 from its junction with the sclerotic: remove the cornea: take carenot to squeeze the eye, or the lens will he driven out instantly: note: i. The a4ueous humour: the transparent watery fluidfilling the anterior cliamber of the eye, andescaping when the cornea is removed. ii. The Fig. 17.—^A diagrammatic section through the human eye passingthrough the centres of the cornea and lens, and through the yellowspot and point of entrance of the optic nerve. A, anterior chamber; Ar, central artery of retina; B, blind spot;C, cornea; Ch, choroid ; CP, ciliary processes; H, hyaloid membrane,enclosing the vitreous humour; I, iris; L, lens; O, optic nerve ;p, posterior chamber; R, retina ; s, sclerotic; SL, suspensory liga-ment ; Y, yellow spot. 3. Pass the handle of a scalpel under the cut edge of the cornea,between it and the iris, and carefully separate the sclerotic fromthe choroid the whole way rov/nd for a distamce of about half anitiich beyond the edge of the cornea. Make four radial cuts, equi-distant from one another, tkrough the margin of the cornea and 90 THE EYE the sclerotic, taking ca/re not to ir^v/re the deeper parts; andextendthe cuts hacic towa/rds the optic nerve. Ga/refvMy peel offthe
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectbiology, bookyear1896
