. Quain's elements of anatomy . egments of two spheres,, of which theanterior is the smaller and more prominent; the segment of the largerposterior opaque sphere corresponds with the limit of the sclerotic coat,and that of the smaller sphere with the cornea. The eyeball measures about an inch across from side to side and fromabove downwards, but not quite a full inch from before back. THE SCLEEOTIC COAT. 391 Except when directed towards near objects, the axes of the eyes arenearly parallel; the optic nerves, on the contrary, diverge nerve enters the corresponding eye about a
. Quain's elements of anatomy . egments of two spheres,, of which theanterior is the smaller and more prominent; the segment of the largerposterior opaque sphere corresponds with the limit of the sclerotic coat,and that of the smaller sphere with the cornea. The eyeball measures about an inch across from side to side and fromabove downwards, but not quite a full inch from before back. THE SCLEEOTIC COAT. 391 Except when directed towards near objects, the axes of the eyes arenearly parallel; the optic nerves, on the contrary, diverge nerve enters the corresponding eye about a tenth of an inch tothe inner or nasal side of the axis of the eyeball. The eyeball consists of three concentric coats, and of certain fluid andsolid parts enclosed by them. The coats are (1) an external fibrouscovering, forming the sclerotic and cornea, (2) a middle vascular, pig-mented, and in part also muscular membrane, the choroid and vis, and (3)an internal nervous and epithelial stratum, the retina. The enclosed Fig. Fig. 326.—Yeetical SECTION of the left okbit and its contents. (Allen Thomson.) Tlie section has been carried first obliquely through the middle of the optic foramenand optic nerve as far as the back of the eyeball, and thence forward through the eyeball,eyelids, &c. a, frontal bone ; b, superior maxillary ; c, eyebrow; d, the upper, and d,the lower eyelid, partially open, showing the section of the tarsi, the eyelashes, &c.; e, e,the reflection of the conjunctiva from the upper and lower eyelids to the surface of theeyeball; /, the levator palpebrte superioris muscle; g, the upper, g, the lower rectusmuscle; h, the inferior oblique muscle divided ; 1, 1, the optic nerve divided in itssheath; 2, the cornea; 2, the sclerotic; 3, aqueous chamber; i, crystalline lens; 5,vitreous chamber refracting media, three in number, are the aqueous humour, the vitreousbody, and the lens. Around the middle of the eyeball there is an adventitious tunic offascia, tunic
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Keywords: ., boo, bookcentury1800, booksubjectanatomy, booksubjecthumananatomy
