The lacunæ of this tissue, which anastomose with each other and communicate directly with the anterior chamber, form Fontana's space (e F, Fig. 67, and e, Fig. 68). Anterior portion and ciliary region of the eye. C, cornea; c S, Schlemm's canal; Os, ora serrata; lp, pectinated ligament; e F, Fontana's space; T, tendinous ring; m, meridional fibres, r, radiating fibres, c, circular fibres of the ciliary muscle; Z, zone of Zinn. The full lines indicate the crystalline lens, iris, and ciliary body in a state of rest; the dotted lines show the same in a state of accommodation. Some of the above-mentioned fibrils are reflected upon the anterior face of the iris, and constitute the pectinated ligament (p). The others penetrate the ciliary muscle, or lose themselves in the walls of the vascular plexus known as Schlemm's canal.1 2 At the junction of the posterior surface of the cornea with the sclerotic, between the fibrous border of Schlemm's canal, the insertion of the iris and the anterior portion of the ciliary body, is found a tendinous ring, described by Gerlach (T, Fig. 67). The connective and elastic tissue, of all the parts here met with, contribute to its formation. This firm ring constitutes the tendinous origin of the ciliary muscle. The ciliary muscle forms another ring, external to the ciliary crown. It has the shape of a triangular bundle, upon meridional section (Figs. 67 and 68). Its shortest side corresponds, in front, to Schlemm's canal, and forms, with its outer, sclerotic side, a right angle, in the normal eye. Its inner face corresponds to the ciliary crown, its apex is directed backward. The fibres of the ciliary muscle may be divided into three parts:1. The most powerful layer (m, Fig. 67, and f, Fig. 68) is nearest the sclerotic. It is composed of a thick layer of fibres having a meridional direction, and forms lamellæ parallel with the sclerotic. These muscular fibres extend backward into the choroid. Here they become dissociated, change direction, and terminate principally in the conjunctival lamellæ of the lamina fusca. This portion of the choroid therefore represents the tendon of the meridional fibres of the ciliary muscle. 2. The second part (r, Fig. 67, and g, Fig. 68) of this muscle contains fibres which are less intimately connected with each other. Their direction deviates more and more from parallelism with the surface of the eyeball from those which are nearest the meridional to those which approach the shortest side of the muscular triangle, and radiate toward the centre of the globe. Hence the fibres of this portion of the muscle terminate near the posterior surface of the ciliary body. 3. The third part of the ciliary muscle is represented by the annular muscle of Müller (c, Fig. 67, and h, Fig. 68). It is composed of circular fibres, which form a ring parallel with the base of the cornea, and of which a section is seen in our figures. They correspond to the shortest side of the triangle formed by the ciliary muscle, and give, to the sclerotico-ciliary angle of the muscle, a shape proportionately less acute as they are more numerous. 1 See, on this topic, Kölliker, Elements of Human Histology. 2 Gerlach, Beitraege zur normalen Anatomie des menschlichen Auges: Leipzig, 1880. Ciliary muscle, after Iwanoff (Graefe and Saemisch, l. c., I., p. 271). a, cornea; b, corneal limb; c, sclerotic; d, iris; e, Fontana's space; f, meridional portion of the ciliary muscle; g, radiating portion of the ciliary muscle; h, annular portion, or circular muscle of Müller; i, anterior tendon of the ciliary muscle; k, posterior tendon of the meridional portion of the ciliary muscle. This part of the ciliary muscle is the most variable. Iwanoff,1 from whose writings we take, in part, this description, has ascertained that in certain myopic eyes the circular fibres may be entirely lacking 1 Iwanoff in Graefe and Saemisch, Handbuch, &c., I., p. 276 (Fig. 6). |