44 



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



Ganglionic Cells of the Fourth Layer. 



Three years ago Professor Betz* published the results of a series of 

 observations which had for their object the more accurate description 

 quantitatively and qualitatively of the histological elements of the 

 cortex. His results were of much interest and importance. Professor 

 Betz terms these great cells " giant pyramids," and gives a short 

 account of their anatomical distribution in man and the higher apes. 

 The important conclusion arrived at by Betz was that the "giant 

 pyramids," in their form and distribution, have the significance of 

 motor cells. We have thought it highly desirable to make a critical 

 examination of the relationship which these ganglionic cells bear to 

 the extensive area defined as the motor area by Ferrier. We shall con- 

 sider these cells under the four heads of Form, Size, Processes, and 

 Distribution. 



1st. Form. This is very variable, as may be seen by reference 

 to Plate 2. The pyramidal form is frequent, whilst a plump body 

 elongated towards either pole approaching in contour somewhat 

 the fusiform character is very typical of these cells. The truly 

 fusiform, or bi-polar cell, is more rarely met with except in the region 

 of the first frontal convolution. The cell itself is devoid of a cell- 

 membrane, and its protoplasmic contents extend for some distance into 

 the very numerous branches arising from it. To this may be attributed 

 the great irregularity in marginal conformation, for the more numerous 

 the branches arising from a cell the more irregular will its outline be. 

 No other nervous elements in the cerebral cortex assume such fantastic 

 outlines, or give rise to so many branching processes. Considering 

 their dimensions and their numerous connections, we may be justified 

 in regarding them as among the most highly integrated anatomical 

 units in the cerebrum. Each cell contains a large round or oval 

 nucleus enclosing a nucleolus. They are peculiarly prone to pigmenta- 

 tion — patches of pigment being found in the protoplasm of most of 

 these cells as a constant and normal constituent, just as it is found 

 universally present in the multipolar cells of the cord. Their imme- 

 diate environments have been already considered in a paper alluded to 

 above ("Relationships of the Nerve-cells to the Lymphatic System"). 



2nd. Size. The measurement of a large number of these cells from 

 the same site in the ascending frontal convolution gave us an average 

 length of 60/*— an average diameter of 25/t, the extremes being 30/t 

 and 96/u, for length, 12ju and 45/t for breadth. Taking, however, a very 

 large selection of cells from various points of this convolution the 

 average length was 71/t, the average width was 35/i, the extremes 

 varying from 36/ito 126/* for length, and from 24/* to 55/t for breadth. 



* " Anatoniischer Nachweis Zweier Gehirncentra." Prof. Betz, Centralblatt f . d. 

 Med. Wissenseh., Aug., 1874. 



