PROJECTION FIBERS. 227 



forms the pyramid of the medulla and the anterior and lateral 

 pyramidal tracts of the spinal cord (Figs. 71, 69, 87, 93 and 102). 

 The fibers of the pyramidal tract, with a few exceptions, cross 

 over to the opposite side; they end in connection with the motor 

 nuclei of cerebral and spinal nerves. Fibers enter the nucleus of 

 the trochlear (or fourth) nerve chiefly on the same side, and a 

 few descend to the motor nuclei of other cerebral nerves and to 

 the gray matter in the spinal cord without decussation; all other 

 pyramidal fibers terminate on the side opposite to their origin. 

 The fibers from the lower one-fourth of the anterior central gyrus, 

 which go to the motor nuclei of the cerebral nerves, to a large extent 



Fig. 71. Diagram of internal capsule in colors. (Original.) 

 RED, motor; BLUE, common sensory; PURPLE, special sensory. 



leave the pyramidal tract high up hi the peduncle and run for 

 some distance through the medial portion of the fillet; they consti- 

 tute Bechterew's accessory lemniscus. This accessory fillet has 

 been recently traced by Flechsig. 



Head and Neck Fibers (Figs. 70, 105 and 106). Those fibers 

 of the pyramidal tract which end in the nuclei of the cerebral 

 and the upper four cervical nerves rise in the lower segment of the 

 motor area, including that part of the anterior central gyrus below 

 the genu inferius of the central sulcus. They run through the 

 genu of the internal capsule to the peduncle and, then, both through 



