GROWTH OF THE CEREBRAL CORTEX 



565 



Chart 3 Giving the corrected thickness of the cortex of the albino rat in 

 sagittal section. Individual entries for the cortical thickness at localities I and 

 V, and the average thickness of the sagittal section (localities I, II, III, IV and 

 V) are given. Based on table 6. o, cortical thickness at locality I. Corrected. 

 X, Cortical thickness at locality V. Corrected. •, Average thickness of the cor- 

 tex in the sagittal section. Corrected. 



For the horizontal section a different brain was necessarily 

 used. In this instance, table 8, brain III d is first in the Group 

 III. Here the correction-coefficient was obtained by formula 

 (3) and the observed values from each of the five localities IX 

 to XIII were corrected accordingly. It is by the use of the 

 measurements thus recorded that the average thickness of the 

 cortex of a brain about two days of age has been obtained, as 

 shown in table 9. 



The entire series has been grouped according to brain weight, 

 beginning with the group 0.1 to 0.2 gram and progressing by 

 increments of 0.1 gram up to 2.0 grams. The normal brain 

 weight at birth lies between 0.2 and 0.3 gram. 



