226 



THE CEREBRUM. 



nucleus pontis; but according to Spitzka some of its fibers end in 

 the nuclei of motor cerebral nerves. Thus it should be noted 

 that, with the exception of those fibers to motor nuclei of the 

 cerebral nerves, each of the three tracts above mentioned, viz., 

 the intermediate; fronto-pontal and temporo-pontal, constitutes 

 a segment of an indirect efferent path which is interrupted in the 

 nucleus pontis and then continued by the axones of that nucleus 

 through the brachium pontis of the cerebellum. It is probable, 

 though not surely established, that the fronto-pontal and temporo- 



Fig. 70. Horizontal and sagittal section through internal capsule, much enlarged. 



(Original.) 



BLUE, Common sensory tracts: Fr. St., Frontal stalk; Par. Stalk, Parietal stalk; Ven- 

 tral stalk. RED, Motor tracts: Fr.-P. Tract, Fronto-pontal tract; Pyr. Tract, Pyramidal 

 tract; Temp. -P. Tr., Temporo-pontal tract ; Interm. Tract, Intermediate tract. PURPLE, 

 Special sense tracts: Opt. R., Occipito-thalamic radiation; Acust. R., Temporo-thalamic 

 radiation. 



pontal tracts are relayed in the corpus striatum or thalamus, as 

 they have been found undegenerated in the base of the peduncle 

 when their cortical origins were destroyed by extensive lesions. 

 The pyramidal tract (tractus cerebro-spinalis pyramidalis) 

 (Figs. 70 and 71) rises in the anterior central gyrus and the pre- 

 central part of the paracentral lobule. It is composed of axones 

 from the giant pyramids and large polymorphous cells of that 

 region. Descending through the corona radiata, genu and 

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

 the pyramidal tract comprises the middle three-fifths of the basis 

 pedunculi, enters into the anterior longitudinal fibers of the pons, 



