GROWTH OF THE CEREBRAL CORTEX 



551 



group. The average measurements for each locality in each 

 plane (section) were then again averaged to give the average 

 thickness of the cortex in the sagittal, frontal and horizontal sec- 

 tions of each brain weight group. In chart 1, these are the values 

 used for the ordinates, the average brain weight of the group 

 being entered on the abscissa. 



01 Q2 Q5 04 OS 06 Q7 



09 10 11 n 1-3 J4 15 16 17 i.8 19 20 



Chart 1 Giving the thickness of the cortex on slide (not corrected) in sagittal, 

 frontal and horizontal sections and the general average thickness, according to 

 brain weight. Based on table 5. • — • — • — S Average thickness of the cortex in 



sagittal section, measured on slide. F Average thickness of the cortex 



in frontal section, measured on slide. H Average thickness of the 



cortex in horizontal section, measured on slide. • "A General average 



thickness of the cortex of three kinds of sections, measured on slide. 



All these data have been tabulated in detail and are on file 

 at The Wistar Institute together with the sections used. The 

 full tables have not been printed here because it is evident that 

 the observations are open to a correction. The sections are from 

 brains that have been subjected to an elaborate technique, while 

 the brain weights are from the fresh specimens, and what we 

 should like to know is the thickness of the cortex in the fresh 

 brain. This can be obtained only by applying a correction to 

 the observed values. 



