xr] Distribution of TI/JK'N of Cortex 255 



of Fusiform Cells. 



This is a deep layer, richly-stocked with medium-sized triangular or spindle-shaped 



cells, having large nuclei, pale-stained protoplasm and the general characters of the same 

 cells in other regions. 



In the lower part there occur some small triradiate elements similar to those seen in 

 the cluustrum. 



TYPE No. 2. 



This type corresponds in distribution with the posterior fibre area, and in describing 

 it, it will suffice if I show the manner in which it differs from the arrangement just 

 considered. The differences affect the external and internal layers of large pyramidal cells 

 and the stellate layer. 



Thus the large external pyramidal cells show a diminution in number and also a reversion 

 to the usual shape. Instead of looking drawn out and laterally compressed, they now 

 present a stouter outline, are more voluminous, and, I think, come to resemble corresponding 

 cells of the audito-psychic cortex. In the parts immediately adjoining the gyri of Heschl 

 a few large chromophilous cells like those characterising the audito-sensory cortex come to 

 view and are no doubt aberrant elements. 



Feebly developed in the anterior insula the stellate layer now becomes a definite 

 lamina and its appearance affords a useful help in differentiating the two areas. 



In the internal layer of large pyramidal cells there is again a reversion to the temporal 

 arrangement, and it is particularly to be noticed that the large chromophilous fusiform 

 cells, of which special mention was made in describing the lamination of the anterior 

 insula, are absent. 



Finally, I would add the general statement that both the fibre arrangement and cell 

 lamination can be satisfactorily seen only in the actual gyri of the insula, in the intervening 

 flat fields the cortical formation exhibits a stunted character like that usually seen in sulci. 



DISTRIBUTION. (See text-figure 15, page 158.) 



The area covered by the anterior type of cortex is considerably more extensive than 

 that coated by the posterior, it comprises the gyrus brevis primus, gyrus brevis secundus, 

 and the gyrus centralis anterior (gyrus brevis tertius), save the uppermost part of each, and 

 the lower extremity of the gyrus centralis posterior (gyrus longus). 



In regard to the uppermost part of the three gyri first-mentioned, the enveloping cortex 

 is of an indiscriminate character ; it is a combination of " frontal " and " anterior insular " 

 types and therefore hard to classify. Along the orbital operculum the transition from 

 "anterior insular" to "intermediate pivcentral " type is abrupt. 



Part of the gyrus transversus shows insular characters and part " frontal." 

 The posterior insular area embraces the whole of the gyrus posterior secundus and the 

 gyrus centralis posterior (gyrus longus), save its upper and lower extremities. 



It is thus seen that the sulcus centralis insulae may be regarded as an approximate 

 albeit not an absolute dividing line between the two areas. 



