52 



NOBUHARU SUITSU 



measure under the microscope (table 5). For the purpose of 

 discussion the data in table 5 have been condensed as in table 6. 

 In this series (table 6) the genu has the greatest thickness and 



TABLE 5 



Shounng the average thickness at the genu, splenium, and truncus in sagittal sections 

 of the rat's callosum according to age 



the truncus the least, but when the values in the first age group 

 are compared with those in the last, it is seen that the ratio of 

 increase is genu 1.56, truncus 1.40, and splenium 1.21. Thus 

 the growth in thickness has been greatest at the frontal end 

 of the callosum and least at the occipital end. 



