. The development of the human body : a manual of human embryology. Embryology; Embryo, Non-Mammalian. 378 THE HISTOGENESIS OF THE NERVOUS SYSTEM outer layer is termed the marginal velum (Randschleier) (Fig. 227, m). The indifferent cells now begin to wander outward to form a definite layer, termed the mantle layer, lying between the marginal velum and the bodies of the ependymal cells (Fig. 228), and when this layer has become well established the cells composing it begin to divide and to differentiate into (1) cells termed neuroblasts, destined to become nerve-cells, and (2) others which app
. The development of the human body : a manual of human embryology. Embryology; Embryo, Non-Mammalian. 378 THE HISTOGENESIS OF THE NERVOUS SYSTEM outer layer is termed the marginal velum (Randschleier) (Fig. 227, m). The indifferent cells now begin to wander outward to form a definite layer, termed the mantle layer, lying between the marginal velum and the bodies of the ependymal cells (Fig. 228), and when this layer has become well established the cells composing it begin to divide and to differentiate into (1) cells termed neuroblasts, destined to become nerve-cells, and (2) others which appear to be supportive in character and are termed neuroglia cells (Fig. 228, B).. 6r ° % ,'. I"' «9 W: cs Fig. 227.—Transverse Section through the Spinal Cord of a Pig Embryo of 30 mm., the Upper Part showing the Appearance produced by the Silver Method of Demonstrating the Neuroglia Fibers. a, Ependyma of floor plate; b, boundary between mantle layer and marginal zone; cs, mesenchymal connective-tissue syncytium; ep, ependymal cells; i, ingrowth of connective tissue; m, marginal velum; mn, mantle layer; mv, mantle layer of floor plate; p, pia mater; r, neuroglia fibers.—(Hardesty.) The latter are for the" most part small and are scattered among the neuroblasts, these, on the other hand, being larger and each early developing a single strong process which grows out into the marginal velum and is known as an axis-cylinder. At a later period the. 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 perfectly resemble the original McMurrich, J. Playfair (James Playfair), 1859-1939. Philadelphia : P. Blakiston's son & co.
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