THE TOTAL NUMBER OF FUNCTIONAL CELLS IN 

 THE CEREBRAL CORTEX OF MAN, AND THE 

 PERCENTAGE OF THE TOTAL VOLUME OF THE 

 CORTEX COMPOSED OF NERVE CELL BODIES, 

 CALCULATED FROM KARL HAMMARBERG'S 

 DATA ; TOGETHER WITH A COMPARISON OF THE 

 NUMBER OF GIANT CELLS WITH THE NUMBER 

 OF PYRAMIDAL FIBERS. 



By Helen Bradford Thompson. 



(From the Neurological Laboratory of the University of Chicago.) 



CONTENTS. 



I. Introduction. 



A. A comparison of the results of the present calculations with those of 



previous observers. 



B. Hammarberg's methods of preparing his material, and of recording 



his observations. 



C. The basis of the subdivision of the cortex into structural regions 



adopted in this paper and a list of the regions. 



D. Hammarberg's enumeration of the cortical layers. 



E. The method by which Hammarberg's data were supplemented when 



incomplete. 

 n. Calculation of the total number of functional nerve cells in the cerebral 

 cortex of man. 



A. The nature and use of the unit column. 



B. Treatment of the large scattered pyramidal cells. 



C. Division of the cortex into functional regions. (Tables I and V). 



D. Verification of the number of cells in the unit columns by means of 



the plates. 



E. The reduction ot the unit columns in sulci. 



F. Determination of the area of the entire cortex, and of each lobe. 



G. Calculation of the average unit column and average percentage re- 



duction for each lobe. 

 H. Calculation of the total number of cells in the cortex. 

 I. Sources of error in the calculation. 



