. The cat : an introduction to the study of backboned animals, especially mammals. Cats; Anatomy, Comparative. chap, ix.] NERVOUS SYSTEM AND ORGANS OF SENSE. 293. The rods stand in close apposition. The cones * are not so close set and do not extend as far outwards as do the rods. Both structures become shorter as they approach the ora serrata. Within the rods and cones is a thin layer of granulated substance, connected with the fibres in which the rods and cones end in- ternally. This layer is the external granular, or outer nuclear layer, within which is the internal granular, or inner nucle
. The cat : an introduction to the study of backboned animals, especially mammals. Cats; Anatomy, Comparative. chap, ix.] NERVOUS SYSTEM AND ORGANS OF SENSE. 293. The rods stand in close apposition. The cones * are not so close set and do not extend as far outwards as do the rods. Both structures become shorter as they approach the ora serrata. Within the rods and cones is a thin layer of granulated substance, connected with the fibres in which the rods and cones end in- ternally. This layer is the external granular, or outer nuclear layer, within which is the internal granular, or inner nuclear layer, formed of nucleated cells and fibres, separated from the former by the inter- granular, or internuclear layer, formed of plexiform tissue enclosing a few nuclei and smooth cells, with coarser fibres running parallel to the surface of the retina. Within the internal granular layer, again, is a thicker inner molecular layer (or internal granulated layer), which contains much connective tissue, within which again is a layer of ganglionic cells, and lastly and most internally, is a layer of fibres of the optic nerve, ramifying on the inner surface of the retina, and con- nected with the ganglia placed ex- ternal to it. This layer of nervous fibres is bounded within by an ex- tremely delicate, glossy membrane, the membrana limitans, which is continued forwards as the pars ciliaris retina?, and becomes con- tinuous with the suspensory ligament of the lens. Doubtless the rods and cones are continuously though complexly connected with the ganglia and fibres of the innermost layer. At the point of entrance of the optic nerve {, at the blind spot) rods and cones are wanting. In the eye, as in the nose and tongue, the special sense is subserved by minute nervous rods proceeding from cells. Filling up the great concavity bounded by the membrana limitans lining the innermost layer of the retina is the vitreous humour (or vitreous body), forming nearly four-fifths of the ball o
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