. On the anatomy of vertebrates [electronic resource] . server computesfive millions of fibres and sixty-two thousand five hundred mil-lions of teeth in the lens of a cod:yet in the living and fresh statethis organ is transparent. The radiating fibres and elong-ated cells of the hyaloid tissue,1with the interstitial i vitreoushumour, present a firmer con-sistency than in the human eye,and show their intimate structure and arrangement more clearlyunder the microscope than in Mammalia. The membranes situated between the retina and sclerotica,called collectively ( choroidtunic, are three in num-b
. On the anatomy of vertebrates [electronic resource] . server computesfive millions of fibres and sixty-two thousand five hundred mil-lions of teeth in the lens of a cod:yet in the living and fresh statethis organ is transparent. The radiating fibres and elong-ated cells of the hyaloid tissue,1with the interstitial i vitreoushumour, present a firmer con-sistency than in the human eye,and show their intimate structure and arrangement more clearlyunder the microscope than in Mammalia. The membranes situated between the retina and sclerotica,called collectively ( choroidtunic, are three in num-ber: the external layer inOsseous Fishes, callede mem-brana argenteaj fig. 216, e, iscomposed chiefly of micro-scopical acicular crystalsreflecting a silvery, or some-times a golden lustre, with adelicate cellular basis, whichassumes more firmness whereit is continued upon the second or middle layeris the 6 membrana vasculosa,seu 4 HalleriJ ib. f, and, asits name implies, is the chiefseat of the ramifications ofthe choroid vessels: it also 218. Arrangement of fibres of lens, Salmon, ccxni. supports the ciliary nerves. The 1 LXV. 334 ANATOMY OF VERTEBRATES. innermost layer is the e membrana pictaj seu RuyscManaJ g,also called f uvea/ which is composed of hexagonal pigment-cells,usually of a deep brown or black colour. In the Grey Shark(Gale us), the silvery layer is laid upon the central surface, notthe periphery of the The formation of the iris, h, by the production of all these mem-branes is well shown in the eye of the Sword-fish Xiphias, fig. 216,where its thick base or i ciliary ligament h overlaps the con-vex border of the bony The membrana argentea uponthe front of the iris gives great brilliancy to the eye, in manyfishes. The pupil, z, is large and usually round: in many Pla-giostomes it is elliptic; in Gal ens it is quadrangular ; in the flat-bodied Skates and Pleuronectidee, that grovel at the bottom andreceive the rays of light from above
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