. The fundus oculi of birds, especially as viewed by the ophthalmoscope; a study in the comparative anatomy and physiology . 16 THE FUNDUS OCULI OF BIRDS The Avian ChoroidThe choroid coat (choroidea) of Birds eyesis always very thin, even in large eyeballs,but thicker than in the Mammals eye. Thevascular, capillary meshes (choriocapillaris)are of irregular size and rather narrow; inStruthio the capillaries are — broader than in other birds. Thespaces between the capillaries are, according is seen at its widest about the time of hatch-ing (when differentiation takes place most
. The fundus oculi of birds, especially as viewed by the ophthalmoscope; a study in the comparative anatomy and physiology . 16 THE FUNDUS OCULI OF BIRDS The Avian ChoroidThe choroid coat (choroidea) of Birds eyesis always very thin, even in large eyeballs,but thicker than in the Mammals eye. Thevascular, capillary meshes (choriocapillaris)are of irregular size and rather narrow; inStruthio the capillaries are — broader than in other birds. Thespaces between the capillaries are, according is seen at its widest about the time of hatch-ing (when differentiation takes place mostactively) and becomes thinner and remainspermanent when the bird is several monthsold. A tapetum is absent in Birds, although theNubian Ostrich has a glass-like layer in thechoroid, of lamellated structure, capable ofreflecting light and producing color inter-. Fig. 7Macroscopical, Postmortem Diagram of the Infulabimacular Fundus and Orbit of the Tern (Sterna hirundo).N, optic nerve entrance; P, pecten; Ft, fovea and area temporalis; Fn, fovea and area nasalis; Ab, band-like area. (After Slonaker.) to Franz, completely free of cells and amount of pigment in the external layeris subject to variation. The thickness of this coat in Passer domesti-cus is about 200 microns. The vessels ofthe choriocapillaris measure from 10 to 20microns in width; between them is a finelypunctate substance. This layer is 7 to 8microns thick. Externally there is an endo-thelial layer, then a net work of fine elasticfibres without cells or pigment; finally, adense plexus of connecting cells. The nerves run within the suprachoroidalspace and send only fine filaments into trabec-ular that form a cavernous system throughoutthe whole coat. Slonaker found the choroid to be enlargedand most vascular (see Fig. 1, just oppositethe fovea, especially in embryonal
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Keywords: ., boo, bookcentury1900, bookdecade1910, booksubjecteye, bookyear1917
