Ill] 



on the Giant ('<//x 



TABLE. 



Extremity of Fissure '2 cells \ 



in 



Mesial surface. 



Margin of hemisphere to buttress. 



Buttress. 



Opposite middle frontal 



Opposite 2nd frontal fissure. 



Lower Extremity of Fissure 



From this table it is evident that the majority of the cells, certainly more than half, reside 

 above the level of the annectant buttress ; the barrenness of the buttress is clearly indicated ; 

 then, after a long stretch, also relatively poor in cells, it is seen how they rapidly disappear as 

 the lower end of the fissure is approached. 



In this enumeration, those small multipolar cells, which I pointed out in the cortex of 

 the annectant buttress and elsewhere, were not taken into account. 



Boundaries of the Area containing Giant Cells. (Plate IX.) 



The limits of the cortex containing these cells can be soon dismissed, because they tally 

 almost exactly with the boundaries of the "precentral" type of arrangement of nerve fibres, 

 and these have already been given. A discrepancy which must be mentioned, however, is that 

 the fibre area is one or two millimetres more extensive than the cell area; to understand 

 this difference we have only to take note of the size and extensive ramifications of the enormous 

 dendrons possessed by these cells, as well as the numerous collaterals given off by their axis 

 cylinder processes, and also remember that the existence of cells of great size has a marked 

 influence on the fibre wealth of the part and apparently makes its presence felt at a con- 

 siderable distance. 



Looking upon the Bet/ cells as discharging elements for motor impulses, it would be 

 interesting to know, along what path or channel the current passes when the cortex is 

 stimulated by unipolar faradisation. Three questions arise. Does the current diffuse through 

 overlying strata to excite the cell body directly? Can it be picked up by superficial cells 

 and passed on indirectly '. Or, falling upon surface ramifications, is it directly led from 

 these to the apical extension of the cell? This is admittedly a difficult problem, but the last 

 to be the most likely hypothesis, and the histological proof of an increase in the size 



52 



