PROJECTION FIBERS. 22$ 



capsule and the mid-brain, and vice versa (Figs. 30 and 42). 

 They connect the cortex, directly or indirectly, with all parts 

 of the body, throwing or projecting a picture of every part and 

 organ upon the cerebral cortex. Many of the fibers are inter- 

 rupted in the basal ganglia, especially of the corticipetal fibers. 

 Within the hemisphere all projection fibers run through one 

 great sheet, the internal capsule, with the exception of the olfactory; 

 but in the mid-brain, they are separated into two great groups 

 the basis pedunculi and the tegmentum, the substantia nigra 

 intervening. 



CORTICIFUGAL, OR MOTOR PROJECTION FIBERS. 



The most important tracts of corticifugal or motor projection 

 fibers are the following, namely, the intermediate tract, the fronto- 

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



The intermediate tract (stratum intermedium pedunculi, Figs. 

 70, 69 and 87) extends from the corpus striatum through the in- 

 ferior lamina of the capsule and the deep part of the basis pedun- 

 culi to the motor cerebral nuclei and to the nucleus pontis, though 

 it is probably relayed in the substantia nigra. From the nucleus 

 pontis axones run by way of the brachium pontis to the cortex 

 of the opposite hemisphere of the cerebellum. The intermediate 

 tract thus forms a segment of an indirect (through the cerebellum) 

 efferent, or motor path. 



The fronto-pontal tract (tractus cerebro-cortico-pontalis jront- 

 alis. Figs, 70, 71, 69 and 87) rises from the cortex of the frontal 

 lobe anterior to the precentral sulci. It tranverses the centrum 

 semiovale, corona radiata, frontal part of the internal capsule 

 and medial one-fifth of the basis pedunculi to the ventral area 

 of the pons, where it terminates in the nucleus pontis (chiefly) 

 and in the nuclei of motor cerebral nerves (Flechsig). It is 

 probably relayed in the thalamus (Beevor and Horsley). 



According to Dejerine, the temporo-pontal tract (tractus cere- 

 bro-cortico-pontalis temporalis, Figs. 70, 71, 69 and 87) extends 

 from the temporal lobe through the inferior lamina (and posterior 

 part of the superior lamina) of the internal capsule and lateral 

 one-fifth of the basis pedunculi to the substantia nigra and the 

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