48 Lewis and Clarke on the Cortical Lamination, §c. [Jan. 24, 



the ascending frontal convolution, interrupted by two groups which 

 occupy the frontal aspect at the origin of the superior and middle 

 frontals, and which at these points appear to run into an extensive 

 area disposed over the posterior third of the two latter convolu- 

 tions. That portion of the ascending frontal marked P (on the chart 

 of the convolutions) has a group of these cells situated along its 

 parietal aspect. The portion intervening between the two lower 

 frontals we have excluded from our scheme, relegating it to a later 

 period, when it will be described in common with the rest of the 

 motor area. Meanwhile we would draw attention to the fact that 

 these cells diminish in size towards the lower extremity of the ascend- 

 ing frontal, as they also do in the areas included in the frontal gyri, as 

 shown by the following table : — 



| Left ascending frontal {upper extremity) . . . 



\ First frontal {area at posterior end) 



Left ascending frontal {lower extremity) . . . 



\ 



In the area at the posterior end of the first frontal (fig. 1, R), the 

 cells assume an elongated contour, a very large majority approaching 

 the spindle form. It is necessary to add that the limits of these areas 

 is not always sharply defined, as occasionally these cells graduate off 

 into smaller and yet smaller elements of the same character, until they 

 eventually disappear. In many instances this fading off at the margin 

 is very noticeable. In other cases, when these ganglionic cells are 

 absent their position is occupied by a series of cells of uniform size, 

 but, whilst exhibiting the general characters of the greater elements, 

 they do not exceed in size the smaller cells of the third layer. These 

 elements, however, invariably occupy the same level as the large 

 ganglionic cell, and we regard them as undeveloped representatives of 

 this series. Within the areas specified these large cells are grouped 

 closely together in twos or threes, and often assume the arrangement 

 of a belt one cell deep. To recapitulate, then, we find these cells form 

 an interrupted series differing thus from the continuous layers above 

 them, and that groupings of cells are thus distributed over certain 

 areas of the cortex closely corresponding to several of the motor 

 centres of Ferrier. Again, we find each group is in itself constituted 

 of numerous secondary groups of cells, <k the nests" of Betz, which 

 differ much in the number of cells forming each group. It must also 

 be noted, that although the giant size of these cells in the upper half 

 of the ascending frontal constitutes a most characteristic feature — the 

 all-important fact to bear in mind is their interrupted distribution, as 



Average Size of 

 Ganglion Cells. 



Largest Cell. 



6(V x 25/jl 

 45^ x 20 fi 

 35u x 17/i 



90u y 45/x 

 69/x x 27fi 

 41/i x 18/i 



