Online Encyclopedia


Online Encyclopedia
Originally appearing in Volume V19, Page 401 of the 1911 Encyclopedia Britannica.
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NERVE CELLS are unipolar, bipolar or multi-polar. Unipolar cells are found in the ganglia on the posterior roots of the spinal nerves, and only give off an axon or axis cylinder process; this, however, soon divides in a T-shaped manner, and all these cells were originally bipolar, though the cell has grown away from its two axons (or, as they are often regarded, axon and dendrite), leaving a stalk joining it to them at right angles. Bipolar cells are found as an embryonic stage of unipolar, though in fish they persist in the spinal ganglia throughout life. They are also some-times found in the sympathetic ganglia. Multi-polar cells are found in the brain and cord, and are best studied in the anterior horns of the grey matter of the latter, where they are nearly visible Cunningham's Text- to the naked eye (see fig. 2). Of their many Book of Anatomy. processes only one is an axon, and it becomes fibre from a Frog. other fibres are called dendrites, and break up (After v.Kolliker.) Into delicate branches some of which surround, but, it is generally believed, are not actually continuous with, neighbouring cells or their processes. It is known that the axons are made up of delicate fibrils, and it is thought by some observers that there is actual continuity between some of these and those of an adjacent neuron, as the combination of a nerve' cell, its axon and dendrites, is called. The cells of Purkinje in the cerebellum show a particularly rich arborization of dendrites (see BRAIN, fig. 7). Nerve cells have generally a large clear nucleus.
End of Article: NERVE CELLS
NERVE (Lat. nervus, Gr. vevpov, a bowstring)

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