GROWTH OF THE CEREBRAL CORTEX 501 



cortical thickness, cortical area, etc., as seen on the slide, into the 

 values for the fresh condition of the material. 



Among above diameters, the L. F was measured in the plane, 

 from which the sagittal sections were taken for the investigations 

 on the cortex, and the diameter W. D. in the plane from which 

 the frontal sections were taken for the same purpose. So the 

 diameter L. F measured in the fresh brain is comparable with 

 the correspondng diameter in the sagittal sections and the diame- 

 ter W. D with that in the frontal sections. The diameters W. B, 

 W. D and L. G are controllable in the horizontal sections, which 

 were taken in a plane passing through the frontal pole and ap- 

 proximately parallel to the basal surface of the brain. The 

 measurements W. B, W. D and L. F were utilized as factors for 

 correction-coefficients used to convert the cortical thickness as 

 measured on the sections into the values for fresh condition, — 

 as will be described in another study. The height is not con- 

 trollable directly in any section prepared by me. The diameters 

 W. B, L. G and Ht. indicate the maximum values in each dimen- 

 sion of the cerebrum and by them it would be possible to outline 

 the shape of a cerebrum of the albino rat, because it is very 

 simple in form. 



These five diameters representing three dimensions of the cere- 

 brum are therefore available for a systematic comparison of the 

 changes which occur in the shape and size of the cerebrum during 

 its growth. 



IV. MEASUREMENTS PRESENTED IN TABLE AND CHART 



Table 3 gives for each brain weight group the data obtained 

 by measurements on fresh brains according to the above men- 

 tioned procedure. The individual measurements have been 

 placed on file at The Wistar Institute. 



Chart 1 shows graphically the linear measurements given in 

 table 3. 



