EYCK. 394 EYE. eludes emphasis, which is only in part atoned for by its beauty and delicacy. His realism, as evinced in such figures as "Adam" and "Eve,' must have been a revelation to contemporaries. His landscapes are well selected, and, like his interiors, form admirable backgrounds for hie pictures, giving unity to the composition. He did nut understand linear perspective, but ren- dered atmospheric gradations with great skill, and understood to a "remarkable degree the hand- ling of light and shade. Most charming of all is his color — bright, but in a low key, and per- vaded by reddish-brown tone, full of light. He was an excellent draughtsman. A school seems to have grown up around Jan van Eyck at Bruges, but none of his pupils were as important as the master, although there were good artists among them. The best were Petrus Christus, Rogier van der Weyden, Hugo van der Goes, Justus van Ghent. (See the article on Painting.) His sister, Mahgareta van Eyck, was also a painter, but of her work nothing is known. Waagen thinks that she painted the miniatures nl' the breviary of the Duke of Bedford, Regent of France, in the Bibliotheque Nationale, Paris. A third brother, Lambekt van Eyck, has been discovered in a book of expenses of Philip the Good, but there is nothing to prove, although this has been surmised by critics, that he was a painter. Bibliography. The chief source of informa- tion on the Van Eyeks is Karel von Mander's Schilderboeck (Haarlem, 1604) ; the author was the Vasari of Flemish and Dutch art, and had many sources of information, both documentary and traditional, now lost. This information is supplemented by occasional entries in contem- porary documents. Of modern authorities the best are: Waagen, Hubert and Johann van Eyck (Breslau, 1822) ; Crowe and Cavalcaselle, Lines of the Early Flemish Painters (London, 1876) ; Hotho, Die Malerschule Huberts van Eyck (Ber- lin, 1S55-58) ; Lalaing, Jean van Eyck (Lille, 1887) : K&mmerer, "Hubert and Jan van Eyck," in Knackfuss, Kunstler-Monographien (Bielefeld, 1898) : and Voll, Die Werke des Jan van Eyck (Strassburg, 1000). EYE (AS. Sage, Goth, augo, OHG. ouga, Ger. Auye, Ieel. auga, OSw. ouga, Sw. oga, Dan. Nor. . Lat. oculus, eye. Gk. (Str<rt, osse, the two eyes, in hureh Sla oko, Skt. aksan, eye). The organ of sight. In tlii- article we shall consider the structure of the human eyeball, and of certain accessory parts it appendages which serve to protect thai organ, ami are essential to the due pei i"i ma nee of iis funct inns. The globe of the eye is placed in the an- terior part of I lie cavity of the orbit, in which it is held in position by its connection with the optic nerve posteriorly, and with the muscles which surround it. and by the eyelids in front. It is further supported behind and on the sides by a quantity of loose fat. which fills up all the interstices of the orbit and facilitates the various movements of which the eye is capable. The fnrin of the eyeball is nearly spherical: but on viewing tl rgar in profile we see that it is com no ed oi enl "ft wo spheres of different diametei Of these the anterior, formed bj (he nea, ha - t he smaller diameter, anil he most prominent, and hence the antero-posterior slightly exceeds (by about a line i the transvi The radius of the posterior or sclerotic segment is about nine- teen-fortieths, and that of the anterior seg- ment about thirteen-fortieths of an inch. When the eyes are in a state of repose, their antero- posterior axes are parallel: the optic nerves, on the other hand, diverge considerably from their commissure within the cavity of the skull to the point where they enter the globe ; consequent- ly, their direction does not coincide with that of the eye. Each nerve enters the back of the globe at a distance of about one-eighth of an inch on the inner side of the anteroposterior axis of the eye. The ej'eball is composed of several investing membranes and of certain transparent struc- tures which are inclosed within them, and which, together with the cornea, act as refractive media of various densities upon the rays of light which enter the eye. SUPERIOR RECTUS OPTIC NERVB OROID INFERIOR RECTUS SCLEROTIC SECTION OF EYEBALL. The outermost coat of the eye is the sclerotic (fromGk. o-kt)p6s, skleros, hard). It is a strong, dense, white, fibrous structure, covering about four -fifths of the eyeball, and leaving a circular deficiency anteriorly, which is occupied by the cornea. Posteriorly, it is perforated by the optic nerve, and it is there continuous with the sheath which that nerve derives from the dura mater, the fibrous investment of the brain and spinal cord. Near the entrance of the nerve, its thick- ness is about one-twentieth of an inch ; from this it diminishes in about one-fortieth; but in front it again becomes thicker, from the tendinous insertions of the straight muscles which blend with it. This coat, by its great strength and comparatively unyielding structure, maintains the inclosed parts in their proper form and serves to protect them from external injuries. The cornea (so called from its horny appear- ance) is a transparent structure, filling tip the aperture left in the anterior part of the sclerotic. lis circumference is overlain 1> the free edge of i lie sclerotic, which in sonic parts presents a groove, SO as to retain it mure firmly; and the connection by continuity of texture between the two structures is so close that they cannot be separated in the dead body without considerable maceration. Tl ornea, in consequence of its ter convexity, projects beyond the line of the sclerotic; the degree of convexity, however, varies in different persons and at different periods of life. It is thicker than any part of the sclerotic, and so strung as tu be able tu resist a fur..' ca pable of rupturing licit tunic. Although beauti fullj transparent ami appearing tu be homogene- ous, it is in reality composed of five layers, clear-
