^22 E. H. J. SCHUSTER. 



(i) The lamina zoualis is about 1 mm. broad. 



(ii) Lamina granularis externa reaches to a depth of about 

 ■3 ram. Its constituent cells are small pyramids and granules ; 

 these vary in size in different regions, and appear to be rather 

 larger on the mesial than on the lateral surface. The largest 

 of the small pyraujids are about 15 x 12 fi. 



(iii) Lamina pyramidalis is about 1 mm. broad, extending 

 from a depth of "o to a depth of I'Smm.; as is usual, the 

 cells increase in size from above downwards. The largest 

 cells in the area figured are about 35 /x in length x 20 /x in 

 breadth ; but this particular strip of cortex, though exception- 

 ally rich in large Betz cells, is rather poorer than others in 

 large pyramids of layer iii. 



(iv) Lamina granularis interna is represented by a few 

 scattered granules in the lower part of layer iii and upper 

 part of layer v. 



(v) Lamina ganglionaris. The Betz cells have already been 

 described; the other cells contained in the layer resemble 

 either those of layer iii or of layer vi. 



(vi) Lamina multiformis is rather poor in cells. These are 

 arranged in regular radial rows, and many of them have 

 strong, downwardly directed processes. 



Anterior Pre central Type (fig. 2). 



The whole depth of the cortex is about 2"2 mm. ; it is built 

 up as follows : 



(i) Lamina zonalis, breadth just over "1 mm. 



(ii) Lamina granularis externa, breadth about "2 mm. 

 This is composed of small pyramids and granule cells, the 

 former measuring 10-15 fx in length by 9-12 /j. in breadth, 

 and the latter being some 9-12 ju in diameter. 



(iii) (iv) and (v) Lamina pyramidalis, lamina granularis 

 interna, lamina ganglionaris are not very clearly separated ; a 



