. The elements of embryology. Chickens -- Embryos. v.] THE CHOROIDAL FISSURE. 91) walls of the cup taking place more rapidly than that of the lens, or in other words to the cavity of the cup dilating. But this growth or this dilatation does not take place equally in all parts of the cup. The walls of the cup rise up all round except that point of the circumference of the cup which is opposite the middle (from side to side) of the stalk. While elsewhere the walls increase rapidly in height, carrying so to speak the lens with them, at this spot, which in the natural position of the eye is on its
. The elements of embryology. Chickens -- Embryos. v.] THE CHOROIDAL FISSURE. 91) walls of the cup taking place more rapidly than that of the lens, or in other words to the cavity of the cup dilating. But this growth or this dilatation does not take place equally in all parts of the cup. The walls of the cup rise up all round except that point of the circumference of the cup which is opposite the middle (from side to side) of the stalk. While elsewhere the walls increase rapidly in height, carrying so to speak the lens with them, at this spot, which in the natural position of the eye is on its under surface, there is no growth: the wall is here imperfect, and a gap is left. Through this gap, which afterwards receives the name of the choroidal fissure, a way is open from the mesoblastic tissue surrounding the optic vesicle and stalk into the interior of the cavity of the cup. Fig. Diagrammatic Representation of the Eye of the Chick of about the third day as seen when the head is viewed from underneath as a transparent object. / the lens, V the cavity of the lens, lying in the hollow of the optic cup. r the anterior, u the posterior wall of the optic cup, c the cavity of the primary optic vesicle, now nearly obliterated. By inadvertence u has been drawn in some places thicker than r, it should have been thinner through- out. s the stalk of the optic cup with s' its cavity, at a lower level than the cup itself and therefore out of focus; the dotted line indicates the continuity of the cavity of the stalk with that of the primary vesicle. The line z, z, through which the section shewn in Fig. 30 F is supposed to be taken, passes through the choroidal fissure. From the manner of its formation the gap or fissure is evidently in a line with the axis of the optic stalk, and in 7—2. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfec
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Keywords: ., bookcentury1800, bookdecade1870, bookpublisherlondo, bookyear1874
