File:A text-book of comparative physiology for students and practitioners of comparative (veterinary) medicine (1890) (14576828040).jpg

Identifier: textbookofcompar00mill (find matches)
Title: A text-book of comparative physiology for students and practitioners of comparative (veterinary) medicine
Year: 1890 (1890s)
Authors: Mills, Wesley, 1847-1915
Subjects: Physiology, Comparative
Publisher: New York, London, D. Appleton and company
Contributing Library: Columbia University Libraries
Digitizing Sponsor: Open Knowledge Commons

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egions. Inasmuch as the cord itselfdoes not fill its bony covering, but floats in fluid and tetheredto the walls by bands of connective tissue, it is well protectedfrom laceration, bruising, or concussion. Like the brain, it hasa protective tough outer membrane (dura mater) with a closer-fitting iuner covering abounding in blood-vessels (pia mater). The white matter of the cord invests the horns of graymatter and is made up of nerve-fibers wanting the outer sheath.Here, as elsewhere, these fibers have only a conducting func-tion ; they do not originate nervous impulses. The gray matter,on the other hand, abounds in cells, some of them with manyprocesses, that can originate, modify, and conduct impulses.Certain well-recognized groups of these cells are arranged incolumns throughout the cord, as shown in the accompany-ing figures. The supporting basis for these cells (neuroglia) isthe most delicate form of connective tissue known. The cord may be regarded either as an instrument for the
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Fio. 32 Fio. 328. THE SPINAL CORD.—GENERAL. 463 Fig. 327.—General view of spinal cord (Chauveau). A, cervical bulb; B, lumbar bulb;C, cauda equina. Fig. 328.—Segment of spinal cord at the cervical bulb, or brachial plexus, showing itsupper face and the roots of the spinal nerves (Chauveau). A, superior roots; J5,inferior roots; C, multiple ganglia of superior roots; D, single ganglion on anexceptional pair; E, £, upper roots passing through the envelopes. reception and generation of impulses independent of the brain;or as a conductor of afferent and efferent impulses destined forthe brain or originating in that organ. As a matter of fact,however, it is better to bear in mind that the cord and brainconstitute one organ or chain of organs, which, as we havelearned from our studies in development, are differentiationsof one common track, originating from the epiblast. While the brain and the cord may act independently to a

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