CORTICAL CKr,L LAMINATION OF PAl'IO HAMADRYAS. 637 



Occipital Type (fig. 10), 





The occipital type is illustrated in lig. 10, which is drawn 

 from the lateral surface of the hemisphere between the sulcus 

 lunatus and tlie upturned end ol the sulcus temporalis superior. 

 The cortex is here TG mm. deep, of which the lamina zonalis 

 occupies rather over "1 mm. The lamina granularis externa 

 is not clearly separated from the subjacent hunina pyramidalis. 

 The latter extends downwards to a depth of 'Vo ram., and its 

 lower half is characterised by the presence of a number of 

 elongated pyramids, which reach a length of 50 fx and more. 

 The lamina granularis interna is narrow but very well marked ; 

 the granules are arranged closely together, and very few cells 

 of other forms are present among tlieni except in so tar as 

 they themselves extend upwards among the bases of the large 

 pyramids. The lower border ol: this layer lies at a depth of 

 •9 mm. The lamina ganglionaris is composed of rather small 

 pyramids ; it is poor in cells and appears as a clear band 

 under the low power of the microscope. It is the conspicuous 

 presence of a layer of large pyramids above the granules, 

 coupled with their conspicuous absence below, which gives 

 the distinctive character to this type of cortex. The lamina 

 multiformis is well developed and about '4 mm. broad. Along 

 its upper border the elements are larger and more triangular, 

 while near its lower edge they are smaller and more fusiform. 



The occipital type, which corresponds to Campbell's visuo- 

 psychic and Brodmann's types 18 and 19, is not of uniform 

 structure over the whole area which it invests. Immediately 

 adjacent to the calcarine area, which it completely surrounds, 

 it is much narrower than in the position selected for illus- 

 tration, fewer cells are present, and the lamina ganglionaris 

 is relatively clearer. As it approaches the temporal .oi" 

 inferior parietal areas which form the greater part of its 

 anterior boundary it assumes more the character of those 



