148 THE CEREBRUM. 



issues from the under surface of the fore-brain at the junction of 

 the hemisphere with the thalamus and, trending toward the 

 median line, descends to the pons. At its superior end it is con- 

 tinuous with the motor tracts of the internal capsule. Four motor 

 tracts make up the basis pedunculi, viz., the intermediate, the 

 temporo-pontal, the pyramidal, and the fronto-pontal. 



The deep portion of each basis pedunculi (Fig. 47) is occupied 

 by the intermediate bundle, whose fibers rise in the corpus striatum 

 and terminate in the nucleus pontis (Flechsig). The superficial 

 portion should be studied in three parts. 



(1) The outer fifth of each basis contains the temporo-pontal 

 tract (tractus cerebro-cortico-pontalis temporalis). It is composed 

 of efferent fibers which rise in the temporal cortex, in the superior, 

 middle and inferior gyri (Dejerine); and, perhaps, in portions 

 of the occipital lobe (Zacher) and the parietal lobe (Sioli). Pro- 

 ceeding through the inferior lamina and the occipital part of the 

 superior lamina of the internal capsule, and through the lateral 

 part of the basis pedunculi, they terminate chiefly in the nucleus 

 of the pons; a few end in the motor nuclei of cerebral nerves 

 (Spitzka). The fibers are probably interrupted and relayed 

 in the thalamus or lentiform nucleus. They form a segment of 

 the indirect motor path. These fibers are medullated later than 

 the pyramidal tract (Flechsig). 



(2) The middle three- fifths of the basis pedunculi (Figs. 47 

 and 48) is occupied by the pyramidal tract (fasciculus longitu- 

 dinalis pyramidalis}. Its fibers rise in the anterior central gyrus 

 of the cerebral cortex; they run through the genu and anterior 

 two-thirds of the occipital part of the internal capsule, form the 

 middle three-fifths of the basis, a part of the anterior longitudinal 

 fibers of the pons, and the pyramid of the medulla. Below the 

 medulla they are continued in the anterior and lateral pyramidal 

 tracts of the spinal cord. Those fibers of the pyramidal tract 

 which innervate the muscles of speech and of the face run through 

 the genu of the internal capsule and constitute the medial portion 

 of the tract in the mid-brain and the accessory lemniscus (of 

 Bechterew). Immediately behind the face fibers, in the capsula 

 interna, and external to them, in the basis pedunculi, are fibers 



