The development of the human body; a manual of human embryology . branches as it does in the adult, but iscontinued on through the cavity of the optic cup () to reach the lens, around which it sends branches toform the tunica vasculosa lentis. According to some authors, the formation of the vitre-ous humor is closely associated with the development ofthis artery, the humor being merely a transudate from it,while others have maintained that it is a derivative of the THE VITREOUS HUMOR. 493 mesoderm which accompanies the vessel, and is thereforeto be regarded as a peculiar gelatinous form
The development of the human body; a manual of human embryology . branches as it does in the adult, but iscontinued on through the cavity of the optic cup () to reach the lens, around which it sends branches toform the tunica vasculosa lentis. According to some authors, the formation of the vitre-ous humor is closely associated with the development ofthis artery, the humor being merely a transudate from it,while others have maintained that it is a derivative of the THE VITREOUS HUMOR. 493 mesoderm which accompanies the vessel, and is thereforeto be regarded as a peculiar gelatinous form of connectivetissue. In the mammalian eye it is difficult to determinethe relative merits of these two views, but the fact thatin the lower vertebrates—the birds, for example—thevitreous humor forms at a time when the optic cup con-tains neither mesoderm cells nor blood-vessels indicates aprobability that neither of them is quite sufficient to ex-plain the observed phenomena. Recently it has beensuggested that it is to the retinal cells that one must look. Fig. 262.—Reconstruction of a Portion of the Eye of an Embryo of , Hyaloid artery; ch, chorioid coat; I, lens; r, retina.—(His.) for the formation of the humor (Rabl), and further ob-servations along this line are desirable. Over the surface of the vitreous humor a structurelessmembrane, known as the hyaloid membrane, is formed,apparently by a condensation of the vitreous humor or asa secretion of the retinal cells, and in the more anteriorportions of the humor fibers appear, extending acrossfrom the ciliary processes to become continuous with thecapsule of the lens (Fig. 263, si). These fibers increase innumber in later stages and represent the suspensory liga-ment of the lens {zonula Zinnii), and spaces which occur 494 THE DEVELOPMENT OF THE HUMAN BODY. between the fibers enlarge to produce a cavity traversedby scattered fibers and known as the canal of Petit. After about the third month the portion of th
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectembryol, bookyear1902
