370 TRACING OF IMPULSES. 



Fronto-pontal (Fig. 106). The impulses originate in the 

 frontal region (?), and descend through corona radiata, the 

 frontal part of the internal capsule, and the medial fifth of the 

 basis pedunculi to the nucleus pontis. Temporo-pontal. They 

 rise in the temporal cortex and run through corona radiata, the 

 occipital part and inferior lamina of the internal capsule, and the 

 lateral fifth of the basis peduncli to the nucleus pontis. Both 

 the fronto-pontal and the temporo-pontal paths are probably 

 relayed in the corpus striatum or the thalamus. Intermediate 

 Bundle. Cortical impulses of unknown origin are received by 

 the corpus striatum and conveyed, by a bundle of centrifugal 

 axones which form the deep portion of the basis pedunculi, to the 

 substantia nigra and then to the nucleus pontis, chiefly of the 

 same side. The impulses thus traverse the internal capsule and a 

 broad but thin area hi the basis pedunculi just ventral to the sub- 

 stantia nigra and dorsal to the pyramidal tract. In all three of 

 these paths the impulses run to the nucleus pontis of the same 

 side and to motor nuclei of the cerebral nerves. Whence they 

 proceed from nucleus pontis: (i) To Spinal Nerves. They run 

 through the brachium pontis to the cerebellar cortex and, thence, 

 continue down the anterior descending cerebello-spinal tract to 

 the anterior gray columna of the spinal cord. Their course from 

 the cerebellar cortex is through the acustico-cerebellar tract and 

 the restiform body, the lateral area of the medulla and the antero- 

 lateral column of the cord. From the gray matter of the spinal 

 cord the impulses are conveyed by the motor fibers of the spinal 

 nerves to the muscles which they supply. (2) To Cerebral Nerves. 

 The impulses run from the synapses formed in the cerebral nuclei, 

 by the fibers of the cerebro-pontal tracts, through the motor 

 fibers of these nerves to their distribution. 



PATHS THROUGH THE RED NUCLEUS (Fig. 106).- 

 There are two, a direct and an indirect. Impulses run from some 

 part of the cerebral cortex to the thalamus and red nucleus or to 

 the corpus striatum and red nucleus. From the red nucleus 

 they pursue either a direct or indirect route. 



(i) Direct Route, The Rubro-spinal Path. By the direct 

 route, impulses run through the crossed descending tract of the 



