Thompson, Cells in tJte Cerebral Cortex of Man. 135 



B. The number of pyramidal fibers supplied to the arm, 

 leg and trunk of one side of the body, was determined by Blocq 

 and Ozanoff,^ to be 79,111. The total number of pyramidal 

 fibers for the limbs and trunk, would be twice this number, or 

 158,222. In addition to this, the pyramidal fibers supplied to 

 the head and neck, for which no data are available, enter into 

 the total number of pyramidal fibers in the body. According 

 to these calculations, the number of giant cells, 159,690, is a 

 little in excess of the number of pyramidal fibers for the limbs 

 and trunk, 158,222. The excess, only 1500, is not sufficient 

 to account for the number of pyramidal fibers which must be 

 assumed for the head and neck. 



Since most of the giant cells are located in the upper and 

 mesial portion of the anterior central gyrus (vide II B), which 

 is the center for the limb and trunk muscles, the correspondence 

 in number between giant cells and pyramidal fibers going to the 

 cord, leads to the conclusion that the giant cells give rise to the 

 pyramidal fibers for the limbs and trunk, while the pyramidal 

 fibers supplied to the head and neck have some other source, 

 probably the large pyramidal cells in the fifth layer of the lower 

 portion of the motor region — the centers for the head and neck 

 movements. 



Tables VII and VIII are added to furnish the details of 

 the calculations from Hammarberg's original numbers, the re- 

 sults of which appear in Tables I and V. 



1 Du nombre comparatif pour Membres superieurs et inferieurs de I'homine 

 des fibres nerveuses d'origine cerebrals destin^e aux mouvements. Gaz. des 

 Hopit. 1892. Sept. 8. 



