194 Ley ton and Sherrington 



column's edge. A few degenerated fibres lie in both ventral columns 

 opposite the deepest part of the ventral fissure. At a level between 2nd 

 and 3rd thoracic segments the degenerations in both lateral columns are 

 found to be very greatly lessened, especially in the left ; and the disparity 

 between the rioht and left lateral column degenerations is more obvious 

 than higher up. A trace of degeneration is still detectable in the left 

 ventral column at the deep part of the ventral fissure's lip. At the mid- 

 thoracic region there is still some degeneration in the pyramidal region of 

 both lateral columns, distinctly heavier on right side than left. In the 

 upper lumbar region degenerated fibres are detectable in the right lateral 

 column's pyramidal region, but none are obvious in the left. Below the 

 3rd lumbar level no trace of deofeneration was discovered. 



Ablation-Experiment 3. Ablation of part of Leg Area 

 from Left Hemisphere (figs. 2, A, and 23). 



Chimpanzee, $ , rather small, well nourished. 



June 25. — -The upper part of gyrus centralis anterior exposed under 

 deep anaesthesia. After reflecting the dura mater the surface of the ex- 

 posed portion of centralis anterior and of the adjoining centralis posterior 

 and of the cortex in front of sulcus precentralis superior was explored with 

 the electrode up to the near neighbourhood of superior longitudinal fissure. 

 Fig. 2, A, indicates the positions of a number of the cortical points tested and 

 their responses. No responses were obtained from centralis posterior even 

 with the second coil of inductorium pushed up to 5 cm. A large part of the 

 leg area cortex was then excised to a depth of about 8 mm. The excision 

 was carried down to the region yielding abdominal wall movements. The 

 points marked 262 and 281 lay in the exposed area, but were not excised. 

 The points marked 313, 339, 269, 292, and 293 were not exposed at this 

 operation. The whole operation was carried out aseptically, and the dural 

 flaps reclosed and stitched, and the wound closed. 



On recovering from the anaesthesia the animal was active, and showed 

 clear paresis in right hind-limb, but it used the limb in climbing and 

 moving about the cage. No paresis detected in fore-limb. The impair- 

 ment of right hind-limb was evidenced in clumsiness as well as weakness, 

 and affected the digits as well as the hip. 



June 26 — Animal lively. Seems more aware of defective control of 

 right leg than yesterday, when it seemed to trust to it, and be unaware 

 of disability in it until it put it to use. Right knee-jerk is distinctly more 

 ample and brisk than left. 



June 27. — Animal lively. Evidently more power and less clumsiness 

 in right leg. 



June 30. — Animal lively; scalp has nearly healed. Climbs about 

 freely, and right leg is much used, and has improved. 



July 10. — Very little noticeable disturbance in right leg in its use as 



