196 Ley ton and Sherrington 



that the top border of lesion is a little over on mesial surface, which it 

 certainly was not when made. The rest of leg area was explored, and gave 

 results a number of which are in the map (fig. 2, A). Centralis posterior 

 still remained quite unresponsive to stimulation. Animal then killed with 

 chloroform. 



Examination of the bulb and cord by Marchi method showed (fig. 23) 

 a degeneration scattered all over the cross-section of the left pyramid, but 

 entirely confined to that. The amount of degeneration appeared to be 

 less than that in the other specimen of leg area lesion and than in the 

 arm area lesions. In the upper cervical region the contralateral degenera- 

 tion at 3rd cervical level shows only a small extension to the margin of 

 the lateral column. There is a small scattered degeneration in ipsilateral 

 lateral column, and a smaller degeneration still in ipsilateral ventral column 

 by the side of the ventral fissure. At the level of the lower part of 1st 

 thoracic segment these degenerations, though they have shifted in position 

 somewhat, the crossed pyramidal especially having spread ventrally, 

 exhibit no obvious diminution. In the mid-thoracic region the ipsilateral 

 lateral column degeneration has the appearance of being a little heavier 

 than in cervical region, but is quite slight, and any increase in it is dubit- 

 able. At the 12th thoracic segment, last thoracic segment but one, the 

 ipsilateral ventral pyramidal degeneration has almost disappeared, but the 

 crossed pyramidal seems still as heavy as anywhere above, and has 

 encroached toward margin of column laterally, and extends farther 

 ventrally. At the 1st sacral level the crossed pyramidal degeneration has 

 become obviously less, but is still extensive ; it has the comma shape noted 

 in the other leg area lesion ; there is still an obvious ipsilateral degenera- 

 tion in the lateral column, but it is quite slight. 



Ablation-Experiment 4. Ablation of part of Leg Area 

 of Left Hemisphere (figs. 24 and 25). 



Troglodytes niger, ^^ , adolescent. 



May 13. — The upper part of centralis anterior of left hemisphere 

 exposed under deep chloroformisation, and with aseptic precautions. 

 Precentralis gyrus and post-centralis explored by faradisation from the 

 superior genu of centralis sulcus up to the mid-line. The motor responses 

 noted and their cortical points mapped (fig. 24), they showed the same 

 general results as obtained in previous experiments. The leg region came 

 down to level of superior genu, which was not well marked, but in its 

 neighbourhood the primary movements of the responses were practically 

 always of hip. Below the hip area, and meeting it, was a transverse strip 

 of the convolution, which evoked movements of abdominal wall. A large 

 vein crossed the gyrus horizontally about 2 mm. above the lower edge of 

 the abdominal wall area. In the upward direction the hip area merged 

 into an area yielding knee movements, and this latter in turn into an 



