GEOWTH OF THE CEEEBEAL COETEX 



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Chart 11 A comparison of the growth curves of the cortical thickness, as 

 observed, with the theoretical growth curve (c) of one diameter of the brain of 

 the albino rat, (c) being the cube root of the ratio of the brain weight (Table 

 14). The cortical thickness and the length of one diameter of the brain at birth 

 were taken as unity on the ordinate. On the abscissa the ratio of brain weight 

 is entered. The dotted line is a theoretical curve which the cortical thickness 

 would have followed if the cortical thickness at 20 days of age were taken as 

 the starting point and it had increased at the same rate as the growth of the 

 brain in diameter. X and X X mark respec tively the ends of the first and the 

 second phases of development in cortical thick ness. Based on table 14. 



ratios given in column C, values which may be taken as repre- 

 senting the rate of increase in one dimension of the brain, if we 

 neglect the shght increase in the specific gravity of the brain sub- 

 stance with advancing age and assimae that the brain form is simi- 

 lar throughout the series. Column E shows the absolute thick- 

 ness of the cortex in each group and column F the ratios of the 

 cortical thickness for each group, compared with the initial cor- 

 tical thickness at birth. 



