The anatomy of the nervous system, from the standpoint of development and function . mb of the internal capsule, the intermediate three-fifthsof the basis pedunculi, the basilar portion of the pons, and the pyramid of themedulla oblongata, and after undergoing a partial decussation are continued intothe spinal cord (Figs. 237, 238). At the pyramidal decussation in the caudal \20 THE NERVOUS SYSTEM part of the medulla oblongata the greater part of the tract crosses to the oppositeside oi the spinal cord and is continued as the lateral corticospinal tract in thelateral funiculus. The smaller par
The anatomy of the nervous system, from the standpoint of development and function . mb of the internal capsule, the intermediate three-fifthsof the basis pedunculi, the basilar portion of the pons, and the pyramid of themedulla oblongata, and after undergoing a partial decussation are continued intothe spinal cord (Figs. 237, 238). At the pyramidal decussation in the caudal \20 THE NERVOUS SYSTEM part of the medulla oblongata the greater part of the tract crosses to the oppositeside oi the spinal cord and is continued as the lateral corticospinal tract in thelateral funiculus. The smaller part is continued directly into the ventral fu-niculus of the same side, as the ventral corticospinal tract. The fibers of theventral tract cross the median plane a few at a time and terminate, as do those ofthe lateral tract, directly or indirectly in synaptic relations with the primarymotor neurons within the anterior gray column (Fig. 239). The ventral tractis not evident as a well-marked bundle below the level of the midthoracic region. Pons Corticobulbar tract. Medulla oblongata Ventral corticospinal tractLateral corticospinal tract— Spinal cord I cntral rootFig. 239.—The corticobulbar and corticospinal tracts. It has long been known that in the higher mammals the lateral pyramidal tract, althoughconsisting predominatingly of crossed fibers, contains a few homolateral fibers also (Simpson,1902). and according to the observations of Dejerine (1914) and other investigators thisholds true for man also. Dejerine speaks of these uncrossed fibers in the lateral corticospinaltract as a third bundle arising out of the motor decussation, and calls it the homolateralcorticospinal fasciculus. A good account of this tract and of the superficially placed bundleof uncrossed pyramidal fibers that is to be found in the ventral part of the lateral funiculusin the cervical portion of the spinal cord is given by Barnes (1901). Neuron II. —To the lower or primary motor ne
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