EYDE, Samu Norwegian chemist and iwakitor: b. Arenctal 1860. He was educated in his native and also 4n Berlin. He was a practising engineer in Norway, Sweden and Germany. With Dr. Christian Birkeland of Christiana, he set about producing fertilizers from the air (nitrogen) and limestone by elec tricity. After a long experimental stage the idea was reduced to practice in 1903, when they began to manufacture the fertilizer with three men and a small motor. Within the following 10 years Eyde had plants aggregating 200,000 horse power, employed 400 chemists, engineers, etc., and about 14,000 other employees. The output of his works reached 2,000 barrels of Norway saltpetre per day. In 1914 he acquired another plant with 200,000 horse power. Notod den, Saaheim and Eydehavn are now towns supported entirely by these new industries. The war of 1914 hindered development along the lines mapped out by Eyde but gave a great impetus to the manufacture of explosives to which much of the capacity of the plants was diverted as early as May 1915.
EYE, the peripheral organ of vision. It re ceives light-energy, transforming it into nerve stimulus, which latter is transferred to the brain by means of nerve fibres.
Anatomy and The human eye has in general a spherical form, with a segment of a smaller sphere superadded ante riorly. The average antero posterior diameter is 2426 mm.; transverse diameter 23.7 mm. The eyeball of a man is slightly larger than that of a woman. The middle point of the cornea is called the anterior pole, diametrically opposite to which on the sclera is the posterior pole. The line of union between the two poles is the geometric axis. The equator of the eye is a circle equidistant from the poles. (Fig. 1).
A shallow, circular furrow (sulcus sclera externus), filled out with conjunctiva, separates the transparent cornea from the opaque sclera. The cornea is elliptical in shape, the horizontal diameter of 12 mm. being slightly greater than the vertical diameter. Between the margin of the
cornea and the equator are the insertion lines of the recti muscles. (Fig. 2).
Posteriorly the optic nerve, with its sheaths, forms a cord, 5 mm. in diameter. Around the nerve some 20 arteries (short posterior ciliary arteries) enter the sclera to supply the chorioid. (Fig. 6). On either side of the nerve, in the horizontal meridan, the long posterior ciliary artery with its nerve pierces the sclera and enters the perichorioidal space. The posterior part of the globe has been called the arterial half, because here nearly all the nutrient blood enters the eyeball. The venous blood leaves by way of the venae vorticosa two superior and two inferior, just behind the equator. (Fig. 3).
The eye is composed of a variety of tissues, and is divided into three main zones according to its development. The posterior zone, the largest, extends from the entrance of the optic nerve to the insertion lines of the recti muscles. Here begins the middle zone, the anterior limits of which are marked by the sulcus sclera ex ternus. The narrow anterior zone embraces cornea and iris. The cornea and sclera make up the firm, fibrous capsule of the eye, lending form and shape and protecting the delicate inner layers from injury.
There are four principal coats to the eye ball, i.e., (1) sclera and cornea (fibrous capsule) ; (2) chorioid (vascular layer) • (3) pigment epithelium; (4) retina. (Fig. 7). In the posterior zone all four coats are easily separated from one another. In the middle zone the sclera undergoes no change, but the other three coats are transformed into one organ, the ciliary body. In the anterior zone the sclera becomes differentiated into the cornea; while elements from the chorioid, pig ment epithelium and retina form the iris.
The contents of the eyeball are the vitreous, the lens and the aqueous. In that part of the eye occupied by the aqueous the iris is sus pended, dividing it into an anterior and a poste rior chamber. (Fig. 1).