ARCHITECTURE. 



207 



In all probability these discrepancies are due to 

 different methods of investigation, and different inter- 

 pretations of the lower boundary of the cortical layer. 

 At least these possible sources of error must be taken 



3.5 



3.0 



2.5 



13 12 II B 9 



FlG. 39. Illustrating the thickness of the human cerebral cortex. 

 Averages from 9 cases : 6 males, 3 females. In each instance 

 the thickness of cortex was obtained by averaging the thick- 

 ness at the summit of the gyrus, at the side of the sulcus, this 

 latter figure being taken twice, and at the bottom of the sulcus. 

 Only the ends of the verticals above 2*4 mm. are drawn. 

 The numbers below the verticals show the localities of the 

 cerebrum to which they apply (see A, B, and C) ; 3 refers to 

 the middle of the insula, and the other numbers are self- 

 explanatory ; A, schema of the lateral view of the hemisphere ; 

 B, the mesal ; C, the ventral. (Donaldson.) 



into account before we attach any significance to the 

 differences in question. The table indicates in th2 first 



