CORTICAL CELL LAMINATION OF PATIO HAMADKYAS. 625 



of fibres^ a type of arrangement wliich, though obvious even 

 in a narrow strip like that figured, becomes very conspicuous 

 when a considerable width of cortex is examined under a low 

 power. 



The posterior orbital type is of practically identical structure 

 with Brodmann's type 11, but it shows some differences in its 

 extent and boundaries. 



According to Brodmann, this type covers the greater part 

 of tlie orbital surface in the hemisphere of Cercopithecus, 

 being absent only from its anterior portion and the gyrus 

 rectus. In Papio a t3'pe of cell-lamination exactly answering 

 to the description given above is found only in the posterior 

 quarter of this part of the hemisphere, and there it extends 

 across the gyrus rectus, and is in contiuuit}'^ with the anterior 

 limbic type over the orbito-rnesial border. In front it extends 

 fui'ther forward along the hiteral than along the mesial 

 bordei", but it gradually changes its character; the internal 

 layer of granules becomes more marked, and the tangential 

 arrangement of the lamina multiformis less marked, till 

 finfilly, at about the position indicated in the figure, it is 

 definitely replaced by front:il or prefrontal cortex, though 

 where the exact boundary may be it is impossible to say 

 owing to the gradual nature of the transition. 



The intermediate precentral area of Campbell is of approxi- 

 mately the same structui-e and extent both in man and iu the 

 higher npes (orang and chimpanzee). In structure it 

 resembles the precentral (motor) cortex in almost all points, 

 except that no giant Betz cells ai-e preseiit in the internal 

 layer of large pyramidal cells. The elements of this layer 

 are smaller and less numerous than those of the outer layer 

 of large pyramids. Between the two layers is a stratum 

 poor in cells, which occupies the position of the layer of 

 stellate (granule) cells present in most other regions. This 

 type of cortex extends from the mesial surface, over the 

 supero-mesial border, then downwards and outwards over the 

 lateral surface, and ends by occupying a considerable area of 

 the orbital face of the hemisphere. On the mesial surface it 



