. Animal biology; Human biology. Parts II & III of First course in biology. Biology. THE NERVOUS SYSTEM 119. FIG. 104. — LARGE NERVE TRUNK, such as supplies the muscles. Cross-section (magnified 6 diam- eters), showing bundles of nerve fibers. (Peabody.) called protoplasm. The protoplasm in nerve cells possesses the most marvelous and varied powers of any known sub- stance, for the nerve cells are the seat of the mind. Nerve Cells and Fibers. — The many branches of nerve cells make them the most remarkable of all cells for irregularity in shape. Since the protoplasm of the cell con- tinues
. Animal biology; Human biology. Parts II & III of First course in biology. Biology. THE NERVOUS SYSTEM 119. FIG. 104. — LARGE NERVE TRUNK, such as supplies the muscles. Cross-section (magnified 6 diam- eters), showing bundles of nerve fibers. (Peabody.) called protoplasm. The protoplasm in nerve cells possesses the most marvelous and varied powers of any known sub- stance, for the nerve cells are the seat of the mind. Nerve Cells and Fibers. — The many branches of nerve cells make them the most remarkable of all cells for irregularity in shape. Since the protoplasm of the cell con- tinues into the fibers, it is plainly wrong to consider the nerve cell as something apart from its fibers. It is not a complete cell without them. A cell usually has many short branches called dcndrons or dendrites (SQQ Fig. 103) for communicating with near-by cells, and one long branch called an axon (Fig. 103) for communicat- ing with distant parts. The axons form X \ / I } I II the fibers that go to the skin, muscles, and other organs. A These long branches, or axons, of nerve cells go all over the body and are often bound together into visible cords called nerves, or nerve trunks (Fig. 104). White and Gray Fibers (Fig. 105).- 6 W Some fibers have a fatty covering sur- FlG. 105. — c, a white fiber with its fatty rounding the thread of protoplasm; they sheath (dark); d, are w}^te ancj glistening, and are called two gray fibers (without sheath), wkite fibers. Others are without this fatty. 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 Bailey, L. H. (Liberty Hyde), 1858-1954. New York, The Macmillan Co.
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