Ill] Olwi-riitioHx on tin' (,'iaitf Cells 33 



\\ e have next to consider tin- variations in magnitude exhibited by cells in different 

 parts of this field. That siu-li variations do occur is well known, and the disparities have been 

 carefully dealt with by Bevan Lewis, Hammarberg, Hetx, anil others. From measurements of a 

 niunlier of cells in sections taken from the fresh unhardened brain and stained by his own 

 method, one which can be highly commended for the purpose, lievaii Lewis has compiled the 

 following dimensional averages: for cells at the upper extremity of the precentral gyrus, (iO/u. 

 by 25^; opposite the superior frontal gyrus, 45 /n by 20 M ; at the lower extremity of the area, 35 p, 

 b\ 17 /j,. And these measurements may be accepted as substantially correct, and as giving a fail- 

 idea of the changes in volume 1 to which the elements are subject. 



Not satisfied, however, with the statement which is generally given, that the size of the 

 cells progressively diminishes from above downward, and thinking that the parallelism between 

 the magnitude of the cell and physiological function might be made nearer than it is at 

 present, I have investigated this matter very closely. And, in making a comparison of the cells 

 in various localities. I have not based my judgments on measurements, a method to which 

 there are obvious objections, but on drawings, that is to say, whenever I have seen a cell of 

 which I have desired to ascertain the comparative size, I have always traced its outlines and 

 processes on to paper, with a camera lucida; and in this manner I have obtained a series of 

 figures all made to the same scale, which admit of a correct and ready judgment on both 

 cell-size and configuration. An analysis of my results shows that previous observers are perfectly 

 correct in saying that the largest cells of all are to be discovered on that part of the mesial 

 surface of the hemisphere coterminous with the preceiitral gyrus. Proceeding from here on 

 to the dorso-lateral surface of the hemisphere, I find that the cells of all the groups which lie 

 above the annectant buttress are also of great size: indeed individual members can be 

 picked out, which are quite as large as any in the paracentral lobule ; but, judged as a whole, 

 I venture to say that the cells in the group immediately above the buttress are appreciably 

 smaller than those of the mesial surface, and also that as we proceed outwards there is a 

 gradual, although slight, diminution 'in the average volume of the cell. On the buttress itself," 

 as I have previously mentioned, the prevalent large cells are pigmies by comparison with 

 the giants above. Below the buttress, where the group formation recommences, we come 

 upon a chain of cells of quite another size, distinctly larger than the prevalent buttress cell, 

 but from :>() to 40 p. c. smaller than those which lie above the buttress. Such cells extend 

 almost to the lower extremity of the fissure of Rolando, and, be it noted, do not lose markedly 

 in magnitude as they descend. Following on these, that is in the lower part of the Rolandic 

 fissure, and also mixed up to a certain extent with the cells of the last mentioned variety, we 

 come upon elements which, although again pigmies in point of size, resemble giant cells in 

 c -oi i figuration, and in wealth of chromophilic particles. 



In explanation of these variations in cell magnitude, I shall, in a later section, produce 

 evidence to support the belief that they may be taken advantage of as a histological 

 basis for determining the exact situation of the different areas of cortex which preside over 

 different muscle groups: thus, I hope to be able to show that the large cells on the mesial 

 surface of the hemisphere control movements of the foot and lower leg: that movements of 

 the thigh and buttock are go\erited by the gnmps of cells on the dorso-lateral surface of the 

 hemisphere above the great Rolandic buttress: that the cells of this buttress stand related 

 to trunk muscles; that the groups of moderately large giant cells below this level dominate 

 movements of the shoulder, arm and neck: and, that the smaller cells at the lower extremity 



c. 5 



