Text-book of ophthalmology . here the anterior extremities of the vasa hyaloidea propria unite withthem and form a specially dense network of vessels surrounding the borderof the lens. In front of the equator of the lens branches run to this vascularnetwork, which come round the anterior border of the ocular cup from thatportion of the mesoderm which afterward forms the iris. They assist in cov-ering the anterior capsule of the lens also with a vascular network. Amongthe vessels derived from the iris are found veins as well as arteries, and theseveins provide for the escape of all the blood, s
Text-book of ophthalmology . here the anterior extremities of the vasa hyaloidea propria unite withthem and form a specially dense network of vessels surrounding the borderof the lens. In front of the equator of the lens branches run to this vascularnetwork, which come round the anterior border of the ocular cup from thatportion of the mesoderm which afterward forms the iris. They assist in cov-ering the anterior capsule of the lens also with a vascular network. Amongthe vessels derived from the iris are found veins as well as arteries, and theseveins provide for the escape of all the blood, since all the other vessels goingto the lens are arteries. The lens in the fetal eye is accordingly surrounded 394 TEXT-BOOK OF OPHTHALMOLOGY by a vascular membrane, the tunica vasculosa lentis, which in the regionoccupied by the pupil bears the name of pupillary membrane (membranapupillaris, P, Fig. 163), while its remaining portion is known as the mem-brana capsularis (C, Fig. 163). The tunica vasculosa lentis disappears in. Fig. 162.—Section through an Eye at a Period of Development Corresponding to that of aHuman Embryo in the Middle of the Third Month. Magnified 73 X 1. The envelope of the ocular vesicle is formed of mesoderm, and in its anterior segment consistsof the cornea, which contains an abundance of nuclei throughout and is separated by a particularlymarked accumulation of nuclei from the posterior segment. In this posterior segment no delimita-tion between sclera and uvea has as yet taken place. The uvea will develop from the inner layerswhich are distinguished by containing more nuclei—a characteristic which is continued over into thehindmost, or uveal, layers of the cornea. At a point corresponding to the anterior margin of the ocularvesicle the mesoderm projects into the interior of the eye, and from the free border of the ring-shapedprocess thus formed (constituting what is later the iris) rise two delicate vascular membranes whichsurround the lens, constit
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Keywords: ., bookcentury1900, bookdecade1910, booksubjecteye, booksubjectophth
