524 NAOKI SUGITA 



IV. THE SECTIONS 



Sagittal sections 



Alter complete fixation of the brain, the sagittal sections were 

 obtained by slicing the right hemisphere in a plane parallel to 

 the mesial surface. The cut passes through the frontal point 

 (S), as shown in figure 1 diagrammatically, and touches tan- 

 gentially the lateral boundary of the infundibulum, while pass- 

 ing sagittally through the olfactory bulb. The plane of this 

 cut is marked with India ink on the brain, by a circumscribing 



Fig. 1 Diagram of the entire brain of the albino rat seen from above, showing 

 the levels from which the sagittal and frontal sections were taken. SS', the 

 sagittal section; FF', the frontal section; 0, middle point of the sagittal fissure. 



hne SS' around the parietal and basal surface of the right hemi- 

 sphere, along which the sagittal section is to be taken, and a 

 slice of the hemisphere, about 2 mm. in thickness, containing 

 the delineated plane in the middle, is cut out and imbedded in 

 paraffine as previously described. From this slice and exactly 

 in the plane determined by the circumscribing line, 6 to 12 sec- 

 tions were cut in series, stained and mounted. From the left 

 hemisphere of the same brain, frontal sections were also taken. 

 Figure 2 is a somewhat diagrammatic picture of the sagittal 

 section from the albino rat brain at about thirty days in age, and 

 is intended to show the cell-lamination of the cortex and the 

 localities at which the thickness of the cortex was measured. 

 Cytoarchitecturally the cortex of the sagittal section is divided 



