File:A text-book of physiology for medical students and physicians (1911) (14592075688).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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ingstructure along which passes the nerve impulse. The arrangementof these fibrils within the cell is not completely known, the resultsobtained varying with the methods employed. A matter of far- 136 PHYSIOLOGY OF CENTRAL NERVOUS SYSTEM. reaching importance on the physiological side is the question ofthe existence of an extracellular nervous network. Most recenthistoiogists agree in the belief that there is a delicate networksurrounding the cells and their protoplasmic processes. Thispericellular net or Golgis net is claimed by some to be a ner-vous structure connecting with the neurofibrils inside the celland forming not only a bond of union between the neurons, butpossibly also an important intercellular nervous structure thatmay play an important role in the functions of the nerve centers.This view is represented schematically in Fig. 64. According toothers, this network around and outside the cells is a supportingtissue simply that takes no part in the activity of the nerve units.
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Fig. 64.—Bethes schema to indicate the connections of the pericellular network:Rz, A sensory cell in the posterior root ganglion; the fibrils in the branch that runs to thecord are indicated as connecting directly with the pericellular network of the motor cells,Gz. General Physiology of the Nerve Cell.—Modern physiologistshave considered the cell body of the neuron, including the den-drites, as the source of the energy displayed by the nervous system,and it has been assumed that this energy arises from chemicalchanges in the nerve cell, as the energy liberated by the musclearises from the chemical changes in its substance. It would followfrom this standpoint that evidences of chemical activity should beobtained from the cells and that these elements should exhibit thephenomenon of fatigue. Regarding this latter point, it is believedin physiology that the nerve cells do show fatigue. The nervecenters fatigue as the result of continuous activity, as is evidentfrom our personal expe

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