File:A text-book of physiology for medical students and physicians (1911) (14755711776).jpg

Identifier: textbookofphysio1911howe (find matches)
Title: A text-book of physiology for medical students and physicians
Year: 1911 (1910s)
Authors: Howell, William H. (William Henry), 1860-1945
Subjects: Physiology
Publisher: Philadelphia, London, W.B. Saunders company
Contributing Library: Columbia University Libraries
Digitizing Sponsor: Open Knowledge Commons

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he axon is a dischargingprocess through which an impulse is sent out from the cell to reachanother neuron or a cell of some other tissue. The neuron, so 130 PROPERTIES OF THE NERVE CELL. 131 far as conduction is concerned, shows a definite polarity, the con-duction in the dendrites being cellulipetal, in the axons, cellulifugai. The neuron doctrine, so far as the name at least is concerned, dates froma general paper by Waldeyer,* in which the newer work up to that time wassummarized. The main facts upon which the conception rests were furnishedby His (1886), to whom we owe the generally accepted belief that the nervefiber (axis cylinder) is an outgrowth from the cell, and secondly by Golgi,Cajal, and a host of other workers, who, by means of the new method of Golgi,demonstrated the wealth of branches of the nerve cells, particularly of thedendrites, and the mode of connection of one nerve unit with another. Theview that these units are anatomically independent and on the embryological
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Fig. 59.- -Motor cell, anterior horn of gray matter of cord. From human fetus (Lenhos-sek): * marks the axon; the other branches are dendrites. side are derived each from a single epiblastic cell (neuroblast) has provedacceptable and most helpful; but the validity of this hypothesis has beencalled into question from time to time. As was stated on p. 128, Bethe hasclaimed that in young animals the nuclei of the neurilemma! sheath mayregenerate a new nerve fiber containing axis cylinder and myelin sheath, andthis fact, if true, at once brings into question the hitherto accepted beliefthat the axis cylinder can be formed only as an outgrowth from a nerve cell.Some histologists—Apathy, Bethe, Nissl—have also attacked the mostfundamental feature of the neuron doctrine—the view, namely, that eachneuron represents an independent anatomical element. These authorscontend that the neurofibrils of the axis cylinder pass through the nerve cellsand enter by way of a network into direct conne

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