A manual of anatomy . ening near its spinal cord endcalled the foramen of Magendie, which communicates with the sub-arachnoid space. This with the foramina of Luschka permits an THE WHITE SUBSTANCE OF THE CEREBRUM 415 interchange of cerebrospinal fluid between the ventricular systemand the lymph spaces of the membranes covering the brain. By thismeans an equilibrium of pressure is estabhshed inside and outside ofthe brain and spinal cord. The spinal canal is a narrow, tube-like space extending the lengthof the spinal cord; it is located in the gray commissure. It tendsto become obliterated mor
A manual of anatomy . ening near its spinal cord endcalled the foramen of Magendie, which communicates with the sub-arachnoid space. This with the foramina of Luschka permits an THE WHITE SUBSTANCE OF THE CEREBRUM 415 interchange of cerebrospinal fluid between the ventricular systemand the lymph spaces of the membranes covering the brain. By thismeans an equilibrium of pressure is estabhshed inside and outside ofthe brain and spinal cord. The spinal canal is a narrow, tube-like space extending the lengthof the spinal cord; it is located in the gray commissure. It tendsto become obliterated more or less after the prime of life. The entire ventricular system is lined with ependymal cells that inthe spinal cord are chiefly simple ciliated cells and in the ventriclessimple squamous, or simple ciliated elements. The white substance of the cerebrum (medulla) consists of my-elinated nerve fibers that are classified according to their connections,into three groups: (i) projection, (2) association, (3) Fig. 301.—The ventricular system of the brain represented in situ. I. The projection fibers are those that pass from the cortex tolower centers (thalamus, midbrain, pons, oblongata) and are centrifu-gal in direction; to these are added the fibers from the lower centersto the cerebral cortex, the corticipetal fibers. These fibers form thebulk of the corona radiata. This is nothing more nor less than thefan-shaped form assumed by the fibers from the various cerebralconvolutions as they pass to, or ascend from, the internal is the fan-shaped collection of fibers dorsal to the internal capsulethat at a more ventral level constitute the internal capsule. The corticifugal fibers are the pyramidal, or great voluntary motorpathway, the corticothalamic, frontopontile, temporopontile, andthe corticifugal fibers of the optic radiation. AH of these indicateby the name the origin and termination, and their respective posi-tions have been discussed in the internal
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