EYE 



He died at Bruges on July 9, 1440. 

 He is represented at his best in the 

 National Gallery, London, by the 

 magnificent picture of John Arnol- 

 fini and his Wife, and at the 

 Louvre by the exquisite Chancellor 

 Rollin Kneeling before the Virgin. 



Of Margaret van Eyck (c. 1377- 

 1430), his sister, nothing is known 

 beyond the bare fact that she also 

 was an excellent painter. Some 

 writers have even questioned her 

 existence. See Hubert and Jan 

 van Eyck : their life and work, 

 W. H. J. Weale, 1908. 



Eye. The organ of vision. Well 

 protected from injury by its situ- 

 ation in the bony orbit, it possesses 

 an extensive range of vision, the 

 movements of the globe being 

 effected by three pairs of opposing 

 muscles. The eyeball consists of 

 segments of two hollow spheres, of 

 which the smaller, representing 

 about one-sixth of the whole, is 

 anterior. This segment is convex 

 anteriorly and projects in front of 

 the remainder of the globe. It is 

 covered by the cornea, which con- 

 sists of five layers of transparent 

 cells, the innermost layer known 

 as Descemet's membrane. 



The posterior and larger sphere, 

 rather longer transversely than in 

 other directions, is formed by three 

 tunics or coats, the sclerotic ex- 

 ternally, the choroid and iris 

 medially, and the retina internally. 

 The sclerotic is white in colour 

 externally, tough and fibrous, and 

 forms the chief means by which the 

 shape of the globe is maintained. 

 It is perforated posteriorly by the 

 optic nerve and by blood-vessels, 

 forming the lamina cribrosa, and is 

 attached internally by a layer of 

 delicate connective tissue (lamina 

 fusca ) to the choroid. The choroid 

 consists mainly of pigment and 

 blood-vessels. Chocolate- brown in 

 colour, it extends forward to the 

 ciliary ligament, where it is con- 



3056 



nected with the iris, and where its 

 inner surface is thrown into folds 

 known as ciliary processes. 



The iris (rainbow) forms a thin 

 contractile curtain, having a per- 

 foration, the pupil, which is slightly 

 to the nasal side of the centre, for 

 the transmission of light. The iris 

 is of different colours in different in- 

 dividuals ; the colour varying from 

 light blue to dark brown according 

 to the amount and position of the 

 pigment contained. In the albino 



EYEBOLT 



the ciliary muscle which surrounds 

 the outer edge of the iris and is 

 more convex when accommodat- 

 ing, that is to say when a near 

 object is being viewed. 



Rays of light entering the eye 

 should be brought to a focus on 

 the retina. If the globe is too 

 long in its antero-posterior dimen- 

 sion, as in the short-sighted, it is 

 necessary to place a concave lens 

 before the eye to throw the focus 

 farther back. With advancing 



this pigment is entirely absent, years the cornea and the crystalline 



lens tend to become flattened, and 



Eye. Sectional diagram showing 



formation and principal parts of 



the eye 



Composed of radiating and circular 

 muscular fibres which are innerv- 

 ated by fibres of the sympathetic 

 nerve and of the third cranial nerve 

 respectively, it regulates the 

 amount of light entering the eye. 



The pupil con- ggjBBSMRig 

 tracts or dilates 

 according as the 

 eye is exposed to 

 a bright or dim 

 light. The iris is 

 immediately i n 

 front of and in 

 contact with the 

 lens. The retina 

 consists of three 

 principal layers, 

 chiefly of nerve 

 tissue. The ex- 

 ternal layer is 

 formedby terminal 

 cells of the optic 

 nerve called from their shape rods 

 and cones. Exactly in the centre 

 of the posterior part of the retina, 

 and in a line with the central axis 

 of the globe, is the yellow- spot in 

 which the sense of vision is most 

 acute. At a distance of one- tenth 

 of an inch to the nasal side of the 

 yellow- spot is the point of en- 

 trance of the optic nerve. It 

 possesses no vision and therefore 

 is known as the blind- spot. 



The refracting media of the eye 

 constitute the contents of the 

 globe and consist of the aqueous 

 humour, the crystalline humour or 

 lens, and the vitreous humour. 

 The aqueous humour fills the space 

 between the cornea and the lens. 

 It is very small in quantity, weigh- 

 ing from 4 to 5 grs. The vitreous 

 humour forms four- fifths of the 

 entire globe. It is perfectly trans- 

 parent, of the consistency of thin 

 jelly, and is enclosed in a delicate 

 transparent membrane. The crys- 

 talline humour is a double convex 

 lens with the greater curvature 

 posteriorly. It is situated im- 

 mediately behind the pupil, and is 

 held in place between the aqueous 

 humour in front and the vitreous 

 humour behind by an elastic cap- 

 sule and a suspensory ligament. 

 It measures about in. across and 

 about i in. antero- posteriorly. Its 

 shape is modified by the action of 



the lens partly loses its ability to 

 alter its shape when accommodat- 

 ing, a condition known as pres- 

 byopia. Therefore, it frequently 

 is necessary, after middle life, to 



Eye, Suffolk. The parish church oi SS. Peter and Paul, 



whose tower is a magnificent specimen o! E. Anglian 



dressed flint work 



use convex lenses when reading or 

 occupied in near work. See Blind - 



ness. H. E. Davison 



Eye. Small hole, or loop, at the 

 top of certain articles. Eyebolts 

 are screw bolts with a ring in them. 

 The eyes of a sail are holes which 

 take the lashings when reefing. A 

 Flemish eye is the end of a rope 

 bent to form a loop. 



Eye. Mun. bor. and market 

 town of Suffolk, England. It stands 

 on an affluent of the river Waveney 

 19 m. N. of Ipswich, on the G.E.R. 

 An ancient town, it has castle ruins, 

 a grammar school founded in 

 1566, a town hall and corn ex- 

 change. Brewing is an industry. 

 Market day, Mon. It gives its name 

 to a co. div. returning one member 

 to Parliament. Pop. 2,001. 



Eyebar. Metal bar with one or 

 both ends enlarged. In the en- 

 larged end a hole is drilled so that 

 by means of a pin or bolt the end of 

 the bar may be secured to another 

 object. Eyebars vary in size, from 

 a fraction of an inch in diameter up 

 to the great eyebars used in the 

 Quebec bridge, each sustaining a 

 pull of 300 tons. 



Eyebolt. Bolt with one end 

 formed like an eye or rigid ring in- 

 stead of an ordinary head. Eye- 

 bolts are used for many purposes, 

 e.g. as door fastenings and attach- 

 ments for stays and guys. 



