. Elements of comparative anatomy. Anatomy, Comparative. VISUAL OEGAN OF VEETEBEATA. 529 line can be made out on the lower and inner side of the rudimentary bulb ; this extends from the optic nerve to the free anterior edge of the choroid. It corresponds to the fissure (choroidal fissure) which was formed when the rudiment of the vitreous body grew into the secondary optic vesicle (s)} and which must therefore affect the retina and the pigmented layer of the choroid (tapetum nigrum). A large number of changes subsequently affect this rudiment of the eye. The anterior edge of the secondary opti
. Elements of comparative anatomy. Anatomy, Comparative. VISUAL OEGAN OF VEETEBEATA. 529 line can be made out on the lower and inner side of the rudimentary bulb ; this extends from the optic nerve to the free anterior edge of the choroid. It corresponds to the fissure (choroidal fissure) which was formed when the rudiment of the vitreous body grew into the secondary optic vesicle (s)} and which must therefore affect the retina and the pigmented layer of the choroid (tapetum nigrum). A large number of changes subsequently affect this rudiment of the eye. The anterior edge of the secondary optic vesicle grows out, together with the tissue that forms the rudimentary choroid, and gives rise to the iris, which bounds the pupil. When the pro- cess of the cutis pushes its way into the secondary optic vesicle, blood-vessels pass (in the Mammalia) into the cavity ; these are dis- tributed in the periphery of the rudiment of the vitreous body, so that they must have a large share in the nutrition and growth of this structure. The lens, also, of the Mammalia, is invested by a vascular capsule of connective tissue, which disappears again before birth ; in some, however, it does not disappear so early. Mullee, W., Die Staniniesentwickelung des Auges der Wirbelthiere. Leipzig, 1875.— Kesslee, L., Zur Entwickelung des Auges der Wirbelthiere. Leipzig, 1877. § 398. As to the form of the bulb, its anterior segment is much flat- tened in Fishes (Fig. 296). The aquatic Amphibia have the bulb flattened anteriorly; the Ophidii and Crocodilini, among the Reptilia, are characterised by a more considerable curvature of the cornea. In most Birds (Fig. 298) the bulb is divided into an anterior and a posterior segment; the former carries the very convex cornea. This form of eye is most marked in the Eaptores, but the cornea is flattened in the Natatores and Grallatores. Among Mammals, also, the spherical form of bulb may undergo great variation in form. The Sclerotic may be formed of vario
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Keywords: ., bookcentury1800, bookdecade1870, booksubjectanatomycomparative
