. The biology of the frog. Frogs. 136 THE BIOLOGY OF THE FROG the neurilemma; the white substance appears at a compara- tively late period. The cells forming the sheath of a nerve arc of mesodermic origin; the nerve fiber being therefore a structure derived from two germ layers. The regeneration of nerve fibers which have been cut in two shows an intimate dependence of the axis cylinder upon ABC. Fig. 48.—Nerve cells and fibers of the frog. A, fresh nerve fiber. B. nerve fiber with the myelin swollen through the absorption of water. C, cross section of nerve fibers. D, ganglion cells, ax, axis
. The biology of the frog. Frogs. 136 THE BIOLOGY OF THE FROG the neurilemma; the white substance appears at a compara- tively late period. The cells forming the sheath of a nerve arc of mesodermic origin; the nerve fiber being therefore a structure derived from two germ layers. The regeneration of nerve fibers which have been cut in two shows an intimate dependence of the axis cylinder upon ABC. Fig. 48.—Nerve cells and fibers of the frog. A, fresh nerve fiber. B. nerve fiber with the myelin swollen through the absorption of water. C, cross section of nerve fibers. D, ganglion cells, ax, axis cylin- der ; , axis cylinder process of ganglion cell; , incisure of Schmidt; , medullary sheath ; n, nucleus; nl, neurilemma ; ; node of Ranvier; , protoplasmic process of ganglion cell. the ganglion cell from which it arises. The portion of the axis cylinder distal to the cut, and longer connected with the nerve cell, degenerates, and becomes replaced by an outgrowth from the proximal part which fol- lows the track of the degenerating fiber until the structure of the whole nerve is restored. This phenomenon is but a special case of the general principle that a portion of a cell. 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 Holmes, Samuel J. (Samuel Jackson), 1868-. New York : The Macmillan company
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Keywords: ., bookauthorholmessamueljsamuelja, bookcentury1900, bookdecade1920
