ix] Intermediate Prccfntral Area 213 



interval or break in which a tow minute stellato, pyramidal, or polymorphous cells are dotted 

 about, and some of these elements encroach upon the pyramidal layers above and below, just as 

 they do in the case of the " precentral " cortex. 



The layer is perhaps denned with greater facility in the intermediate than in the typical 

 "precentral" field, but its poor development compared with other regions is a noteworthy feature 

 of the combined " precentral " areas l . 



Internal Layer of Large Pyramidal Cells. 



Here the resemblance between the " precentral " and " intermediate " types of cortex 

 erases. The presence of the giant cells of Betz in the former and their complete absence in 

 the latter constitutes a fundamental point of difference. Cells of pyramidal or pear form to 

 which the designation " large " is applicable are present, however, in the " intermediate " 

 cortex, but these do not approach the cells of Betz in size and are even appreciably smaller 

 than the elements in the fourth or outer layer of large pyramidal cells : they are likewise 

 distinctly less numerous than the latter cells, although they are possessed of chromophilic 

 elements arranged in a similar manner, and again tend to preserve a uniformity of size ; all 

 features serving further to distinguish this part from the remaining anterior frontal cortex. 



It was noted in the description of the fibre-arrangement that the " intermediate precentral " 

 cortex shared with other regions a reduplication of the line of Baillarger : this line is now 

 found to correspond in point of level with the deep layer of large pyramidal cells, just in the 

 same way as the outer line corresponds with the external large cell layer. 



Layer of Fusiform Cells. 



Following the deep layer of large pyramidal cells is a distinct and deep stratum of fusiform 

 or polymorphous elements, arranged as usual in columns determined by the radiations of 

 Meynert, but possessing no distinctive characters. 



DISTRIBUTION. (Plate XXII.) 



The field covered by the type of cortex of which the fibre and cell characters have been 

 just described ranges as a zone between 3'5 and 1 cm. in width, placed after the manner 

 of a buffer in front of the " precentral " area proper. In addition, and this is a point of 

 special importance, it reaches downwards and forwards to the orbital surface of the hemisphere. 



The distribution of the area is never exactly alike in any two brains, nor does the 

 anterior boundary always pursue the same course, but the following description is compounded 

 from the examination of all the human brains employed in this investigation and may convey 

 an idea of its average extent. 



Starting with that part on the mesial surface of the hemisphere ; the area here attains 

 great breadth, usually the line of its anterior limit lies in the hinder part of the marginal gyrus 

 and may be placed quite three centimetres in advance of the " precentral " area. The lower 

 boundary (on the same surface) is generally formed by the calloso-marginal fissure, but in the 



1 A well-developed stellate layer is found throughout the parietal, temporal, and occipital lobes, and, as I shall 

 mention later, the same layer increases in representation as we proceed forward in the frontal lobe. The lirnbic 

 lobe and parts of the insula may be pointed to as regions iu which the layer is either absent or very difficult to define. 



