632 E. H. J. SCIIUSTEK. 



of the g'ji'us centralis posterior than at the smniiiit of the 

 gyrus. He thus distinguishes two types — No. 1 clothing the 

 summit of the gyrus, and No. 2 its posterior lip. I do not 

 find that this is the case in Papio. Here the post-central 

 type is at its best in the middle portion of the gyrus, becomes 

 less well-developed near the posterior border, and as it passes 

 downwards into the intra-parietal fissure it loses its distinctive 

 features as it changes into the neighbouring type. A gradual 

 reduction of the size and numbers of these large cells, par- 

 ticularly those of the lamina ganglionaris, can also be 

 observed as one passes downwards over the lateral surface ; 

 they are largest and numerous in the upper half of the gyrus, 

 and become very much less conspicuous near the lower end 

 of the sulcus centralis. On the mesial surface the large cells 

 of the lamina ganglionaris are particularly well represented, 

 while those of the lamina pyramidalis inferior are neither so 

 large nor so numerous. 



Extent of the Post-central Type. — The post-central 

 cortex, modified locally ;is described above, occupies on the 

 mesial surface the posterior portion of the para-central lobule. 

 On the lateral surface it extends anteriorly to the bottom of 

 the sulcus centralis, and occupies the greater part of the 

 gyrus centralis posterior. Above, where the sulcus intra- 

 parietalis bends backwards, it passes into the superior parietal 

 type, while below it extends in front of the lower end tif the 

 sulcus centralis, and becomes continuous anteriorly with the 

 lower poi'tion of the anterior precentral, while posteriorly it 

 changes into the inferior parietal cortex. 



Superior Parietal Type (fig. 7). 



The superior parietal type is illustrated in fig. 7. The 

 general plan of its layers and their relative extent is very 

 much the same as that of the post-central type. The most 



