THE STRUCTURE OF THE CEREBRAL CORTEX 273 



mapped out into areas, each of which is defined by the arrange- 

 ment of the layers of cortical cells and fibers. 



Brodmann (Figs. 128, 129) divides the cerebral hemisphere 

 into eleven general regions, which he says are recognizable more 

 or less clearly throughout the entire group of mammals. These 

 are: 



1. Regio postcentralis (tactile region). 



2. Regio precentralis (motor region). 



3. Regio frontalis (frontal association center). 



4. Regio insularis (insula). 



5. Regio parietalis (parietal association center). 



6. Regio temporalis (auditory region). 



7. Regio occipitalis (visual region). 



8. Regio cingularis (supracallosal part of limbic lobe). 



9. Regio retrosplenialis (postcallosal part of limbic lobe). 



10. Regio hippocampica (gyrus hippocampi and hippocampus). 



11. Regio olfactoria (uncus, amygdala, tuberculum olfactorium). 



In the list as here given Brodmann's names of the regions are 

 given, and in parenthesis is added a brief description of each 

 region. Regions 8, 9, 10, and 11 are all concerned with the 

 olfactory reactions, though region 8 only to a small extent. 

 Region 11 is only in part cortical (the uncus); the other parts 

 of this region are subcortical olfactory centers. The specific 

 sensory and motor projection centers (see p. 165) lie within their 

 respective regions, as designated, but they do not occupy the 

 whole of their regions. On the basis of the arrangement of their 

 cells and fibers these regions are further subdivided by Brod- 

 mann into upward of 50 areas or fields, as shown in Figs. 130 

 and 131. The areas are less uniformly developed in different 

 animals than are the general regions, though many of them are 

 very constantly present. 



Bolton, Campbell, Ramon y Cajal, Vogt, Elliot Smith, and 

 many others have investigated the lamination of the cerebral 

 cortex in man and other mammals, and many charts similar to 

 those here presented have been published. The conclusions 

 reached by these authors do not agree in all respects (particu- 

 larly in the number of areas separately recognized and the 

 nomenclature of the layers of cells and fibers in the various 

 regions) ; nevertheless there is a sufficiently close general agree- 

 ment to make it evident that there is a definite structural pattern 



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