. Kirkes' handbook of physiology . ceed to thespinal cord, and are there represented as the pyramidal tracts. MOTOR AREAS OF THE HUMAN BRAIN 583 This is the reason that movements are produced on stimulation of the whitematter after the superficial gray matter of the animals brain has been sliced off. These motor fibers are those which arise from the pyramidal cells of thecortex. From the motor area of the cortex they converge to the internal cap-sules, and pass down to the crus. In the internal capsule the fibers which passto the pyramidal tracts of the spinal cord occupy that part known as th
. Kirkes' handbook of physiology . ceed to thespinal cord, and are there represented as the pyramidal tracts. MOTOR AREAS OF THE HUMAN BRAIN 583 This is the reason that movements are produced on stimulation of the whitematter after the superficial gray matter of the animals brain has been sliced off. These motor fibers are those which arise from the pyramidal cells of thecortex. From the motor area of the cortex they converge to the internal cap-sules, and pass down to the crus. In the internal capsule the fibers which passto the pyramidal tracts of the spinal cord occupy that part known as the knee(genu) and the anterior two-thirds of the posterior limb, figure 414. In thisdistrict the fibers for the face, arm, and leg are in this relation: those for theface and tongue are just at the knee, and below or behind them come first thefibers for the arm and then those for the leg. The more accurately known arrangements of these fibers in the monkeysbrain, named in order, from above down, are those for the eye, head, tongue,. Fig. 414.—Diagram to Show the Relative Positions of the Several Motor Tracts in TheirCourse from the Cortex to the Crus. The section through the convolution is vertical; that throughthe internal capsule, IC, horizontal; that through the crus again vertical. CN, caudate nucleus;O TH, optic thalamus; L2 and L3, middle and outer part of lenticular nucleus; f, a, /, face, arm,and leg fibers. The words in italics indicate corresponding cortical centers. (Gowers.) mouth, shoulder, elbow, digits, abdomen, lip, knee, digits. These fibers comefor the most part from the portion of the cortex on either side of the fissure ofRolando, but chiefly from the anterior central gyrus, hence called the Rolan-dic area. But the areas for the head and eyes lie more anteriorly in thefrontal lobe, to the front of the precentral sulcus—that for the head abovethat for the eyes, and an area for the trunk (not indicated in the figure 414)is situated more toward the middle li
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