STRUCTURAL ARRANGEMENTS OF CEREBRUM 487 



A careful study of the histology of the different parts of the cortex 

 in man enables us to distinguish certain types of structure characteristic 

 of various regions of the grey matter. In attempting by such means 

 an histological localisation of functions we have to take into account : 



(a) The thickness of the cortex. 



(i) 

 0-25 



(2) 

 0-52 



fO'21 



0-21(1 



0-28 



(4) 

 0'14 



(5) 

 0-28 



FIG. 221 A. Visuo -sensory. 



FIG. 22 IB. Visuo -psychic. 



(6) The relative thickness of the various layers. 



(c) The character of the cells found in the various layers. 



(d) The arrangement and degree of development of the systems of 

 medullated fibres, both radial and transverse. 



The possibilities in such a method are at once apparent if, as in 

 Figs. 220 and 221, we compare the structure of the cortex from, e.g., 

 the pre-central motor convolution, the visuo -sensory area of the 

 occipital convolution, and the ' visuo-psychic ' area. The finer differ- 

 ences are not so readily perceptible without careful study and measure- 



