50 



NOBUHAKU SUITSU 



Accordino- to the opinion of Watson and other authors, the 

 psychical hfe of the rat reaches a high degree of development by 

 the twenty-seventh day, and I have also noted that at this time 

 the myelinated fibers are evenly distributed throughout the 



7 

 6 

 6 

 4 



S 

 2 

 I 







.1 i .3 .4 5 .6 .7 .8 .9 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 



Chart 4 Showing the ratios of the values for the callosal area, total brain 

 area, and cortical area (sagittal section) of the albino rat, according to the 

 brain weight. (7, the ratios of the computed callosal area; B, the ratios of the 

 computed total brain area; A, the ratios of the computed cortical area in sagittal 

 section. Albino rat. 



TABLE 4 



Giving from birth to maturity the ratios of the callosal area, of the total brain area, 



and of the cortical area in sagittal section on brain weight. All values are 



calculated according to each brain weight group. Albino rat 



