THE NERVOUS SYSTEM
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former is the source of the nerves entering the brachial plexus, the latter of the fibers going to the sciatic plexus.
Remove the cord from the neural canal, strip off the meninges, and note that the cord rapidly diminishes in size in the posterior lumbar region, finally terminating in the slender thread-like filum termmale. The posterior spinal nerve roots proceed caudally, accompanied by the filum terminale, for a considerable distance from their attachment to the cord. These roots constitute the cauda equina, so called from its resemblance to a horse's tail.
Exercise XXXI. Draw a cross section of the spinal cord to show the origins of the spinal nerves, the spinal ganglia, etc.
