THE FOEE-BEAIN 



535 



remaining tenth part, which never even during embryonic develop- 

 ment presents a six -layer structure, includes the cortex of the 

 olfactory bulb, hippocampus, dentate fascia, etc. These portions 

 were termed heterogenetic cortical areas by Brodmann in contra- 

 distinction to the former, which he termed homogenetic cortical 

 areas. 



The various cortical regions differ from one another both in 

 the characters of the cell layers and in the characters of the 



Fio. 268. Transverse section of cortex of calcarine fissure from a human foetus of eight months. 

 Cortical region in which the fundamental cytotectonic primitive type of six layers (to right) 

 is directly -continuous at the point indicated by arrows with the eight-layered cytotectonic 

 type proper to the grey matter of the area striata of the calcarine fissure. (Brodmann.) The 

 respective layers are : I, lamina zonalis ; II, lamina granularis externa ; III, lamina pyramid- 

 alis ; IV, lamina granularis interna ; IVa, sublamina granularis int. superficialis ; 1V6, sub- 

 lamina granularis intermedia (Stria Gennari s. Vicq d'Azyri); TVc, sublamina granularis int. 



jrofunda ; V, lamina ganglionaris ; VI, lamina multiformis ; Via, sublamina triangularis ; 

 T , sublamina fusiformis. 



nerve -fibres they contain, and in studying the latter different 

 structural types can also be distinguished ; Brodmann has studied 

 the my do-architecture of the cerebral cortex as well as its cyto- 

 architecture. To enter into details would exceed the limits of 

 our subject, and we can only refer the student to Fig. 272, which 

 shows diagrammatically the combined results of the study of the 

 cells by Golgi's and Nissl's methods, and of the nerve-fibres by 

 Weigert's method (0. Vogt). 



On the basis of the results obtained from studying the cyto- 



