STUDIES OF CEREBRAL FUNCTION. IX 33 



Time, 



Errors, 



Trials, 



The results of this analysis indicated that the inclusion in 

 the series of animals with lesions in the archipallium or 

 thalamus did not significantly alter the results from those 

 which would have been obtained had only cases with lesions in 

 the neocortex been included in all computation of constants. 

 Correction for subcortical injury slightly raised the correla- 

 tions with extent of destruction and indicated that "if lesions 

 to internal structures could be accurately evaluated, the 

 method would most probably reveal a still closer corre- 

 spondence between learning ability and amount of functional 

 tissue.' ' 



"We have instituted similar controls for the present data. 

 The possibly significant subcortical structures, septum, 

 caudate and lenticular nuclei, fornix, hippocampal lobes, col- 

 liculi, habenulae, optic paths to the thalamus, anterior, 

 median, and lateral thalamic nuclei, lateral and median 

 geniculate bodies were represented on diagrams and three 

 arbitrary grades of severity assigned to each. All brains 

 were reexamined carefully for subcortical injuries and the 

 amount of destruction in each of the above structures was 

 graded and listed. 



All cases in which there was no subcortical injury or at 

 most slight degeneration in the dorsal convexities of the 

 hippocampal lobes were selected. With these the correlations 

 between extent of cortical destruction and errors in learn- 

 ing were computed. These constants are listed in table 16, 

 in comparison with the constants computed from all cases. 

 The elimination of the animals with significant subcortical 

 lesions reduces the correlations very slightly, but since the 

 cases with most extensive subcortical destruction have also 

 the more severe cortical injuries, this procedure reduces the 

 range of variation and the reduction in correlation is no 

 more than would be expected from the reduction in range 

 alone. 



THE JOURNAL OF COMPARATIVE NEUROLOGY, VOL. 57, NO. 1 



