. Applied anatomy and kinesiology. e 44 MUSCULAR CONTROL they join the posterior root has an enlargement upon it that iscalled a spinal ganglion. The four roots and the two fissures divide the outer or whitepart of the cord into six columns that extend its whole length: two anterior, two lateral, and twoposterior. Microscopic study of thestructure of these white columns showsit to be composed of medullated nervefibers, each of which has the structureof the main fiber shown in Fig. medullary sheath is what givesthis part of the cord its white appear-ance, leading the early anatomists tob
. Applied anatomy and kinesiology. e 44 MUSCULAR CONTROL they join the posterior root has an enlargement upon it that iscalled a spinal ganglion. The four roots and the two fissures divide the outer or whitepart of the cord into six columns that extend its whole length: two anterior, two lateral, and twoposterior. Microscopic study of thestructure of these white columns showsit to be composed of medullated nervefibers, each of which has the structureof the main fiber shown in Fig. medullary sheath is what givesthis part of the cord its white appear-ance, leading the early anatomists tobelieve that there are two kinds ofnerve substance, white and gray. Look-ing at a cross-section of the cord in amicroscope we see cross-sections ofthese nerve fibers, each one appearing as a circle with a dot in thecentre (Fig. 20). The circle is the neurilemma and the dot is theaxis-cylinder. The greater portion of fibers seen in any section passin a vertical direction; a smaller number are usually seen passingacross Fig. 20. — Cross-section of awhite column of the spinal cord.(Klein.)
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