536 NAOKI SUGITA 



Locality IX. The line IX-IX' has been measured through the 

 tip of the frontal pole along: the line of the cell radiation. This 

 measurement corresponds nearly to that at /-/' in the sagittal 

 section but lies a little nearer the median plane. Here the lam. 

 pyr. occupies about one-fifth of the total thickness, the lam. gran, 

 int. is thin, while the lam. gang, as well as the lam. mult, are 

 thick, the latter being represented here by one layer. 



Locality X. The line X-X' has been measured at the middle 

 of the area SS'-TT'. The line X-X' was determined by joining 

 the point midway between the frontal border of the cornu Am- 

 monis and the tip of the cortex at PP', with the lateral cortex 

 by a line perpendicular to its ectal surface. In this part, just 

 as in the corresponding area LL'~MM' in figure 4, the lam. gran, 

 int. increases its thickness considerably. 



Locality XL This has been measured, like locality III, at 

 the level of the forepart of the cornu Ammonis where the cere- 

 bral cortex is becoming gradually thinner. 



Locahty XIII. Near the occipital pole of the hemisphere, 

 this line XIII-XIII' has been measured at the latero-caudal point 

 where the cerebellum and the occipital lobe come into contact. * 

 This locahty is situated between V and WW and here the light 

 cell-free band, corresponding to the position of the lam. gran, 

 int., is clearly marked. 



Locality XII. This locality has been measured about mid- 

 way between localities XI and XIII, near the fissura rhinalis 

 {V). This corresponds roughly to the locahty VIII in the frontal 

 section. For convenience of comparison I averaged the five 

 measurements here described and this value is named the ''aver- 

 age thickness of the cerebral cortex in the horizontal section." " 



The measurements at localities IX-X-XI-XII-XIII in the 

 horizontal section, like those at localities I-II-III-IV-V in the 

 sagittal section, both reveal a gradual decrease in the thickness 

 of the cortex from the frontal to the occipital pole. By the 

 thickness at IX and X the development of the frontal cortex, 

 by the thickness at XI the development of the temporal cortex, 

 and by the thickness at XII and XIII the development of the 

 occipital cortex can be judged. 



