File:Physiology and biochemistry in modern medicine (1918) (14594968528).jpg

Identifier: physiologybioche00macl (find matches)
Title: Physiology and biochemistry in modern medicine
Year: 1918 (1910s)
Authors: Macleod, John James Rickard, 1876-1935 Pearce, R. G. (Roy Gentry), 1884-
Subjects: Physiology Biochemistry
Publisher: St. Louis : Mosby
Contributing Library: Columbia University Libraries
Digitizing Sponsor: Open Knowledge Commons

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horn, stained to show Nissls granules. a, the axon. (From Howell.) mals, this function is probably the most important which the cell per-forms, for it has been found by separating the ganglia from their bloodsupply in the frog that, although the cells degenerate in about twoweeks, sensory impulses continue to be transmitted through the gan-glia. Similar observations have been made in the case of the crab, inwhich the cell bodies of the neurons lie on the surface of the ganglion 800 THE CENTRAL NERVOUS SYSTEM mass, from which they can be separated, leaving merely the neuropile,through which, however, the reflex continues to be conveyed. After atime, of course in this case also the reflex disappears, becausean axon can not live indefinitely after it has been separated from itsnerve cell. These facts regarding the general function of the nerve cell arouseour curiosity as to its morphologic structure. When nerve cells arefixed and stained in various ways they show certain elements in the
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Fig. 209.—Part of an anterior cornual cell from the calfs spinal cord, stained to show neurofibrils:ax, axon; a, b, c, dendrites. (From Bethe.) cytoplasm—namely, (1) large granules or masses, which stain deeplywith basic dyes and are called Nissl bodies (Fig. 208), and (2) a finenetwork of fibrils passing through the cell substance from one process ordendrite to another—neurofibrils (Fig. 209). These appearances in fixedand stained preparations are possibly, however, entirely artificial; for whennerve cells are preserved in a living state—by being suspended in some ofthe animals own lymph or blood serum—it is found, when they are ex-amined by the aid of the ultramicroseppe (seo page 52); that the cytoplasm Tin: PROPERTIES OF BACH PART OF THE REFLEX ARC 801 is composed of a viscous fluid full of extremely minute granules, each ofwhich apparently consists of a colloidal solution surrounded by a lipoidenvelope (Fig. 210). When the temperature is raised, the granules dis-appear,

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