192 Ley ton and Sherrington 



The precentralis throughout the region explored outside the lesion with 

 the electrodes was found to consist of a continuous field of excitability for 

 the whole length examined in it. The strip of cortex above the former 

 lesion was then excised to the limit shown in fig. 5, A, by the broken line 

 marked 8, iv. From the old lesion the electrodes never obtained responses, 

 although plunged deeply into the tissue, and although both the single and 

 double electrodes with strong stimuli were used. 



On recovery from the operation narcosis the animal showed no impair- 

 ment in the motility of right arm. Grapes and pieces of grape and maize- 

 grains were picked up as successfully as before. Once it was noted that 

 the animal having picked up a grape-berry carried it by right hand to the 

 base of the forehead at root of nose, seemingly instead of to the mouth. 

 But on many other occasions the morsel was carried by the hand accurately 

 and quickly to the mouth. The following morning, AjDril 10th, the animal 

 was seen to pick something out of the inner canthus of the left eye with 

 the tip of the right index finger. The left arm had a good grasp ; there 

 was much less wrist-drop ; elbow was certainly moved freely ; but there 

 seemed some misjudgment of the position of the left hand. 



May 4. — The animal now uses both hands and arms well. Employs 

 either hand in feeding himself with banana or grapes. Peels banana, hold- 

 ing it in one hand and stripping off the peel with the other. 



Under deep narcosis the central region of left hemisphere laid bare 

 (fig. 5, C). Faradisation of centralis anterior above the excised area from 

 border of the old lesion to superior genu evoked merest trace of shoulder 

 movement and no trace of movement elsewhere in arm, but gave near edge 

 of lesion and for some distance above it movement of chest muscles, uni- 

 lateral and crossed, and not otherwise interfering with respiratory rhythm 

 of chest. Higher still centralis anterior gave movements of abdominal wall, 

 also unilateral and crossed. Higher still the leg area gave usual results. 

 The cortex adjoining lower edge of lesion evoked retraction of opposite 

 angle of mouth with some inversion of upper lip. From the cortex in 

 front of the lesion no response was obtainable. From the centralis posterior 

 likewise no responsive movement was elicitable when faradised under 

 ordinary conditions, but on faradising it opposite the leg area immediately 

 after a precurrent stimulation of centralis anterior closely on the same 

 level there seemed distinct re-induction of the same movement which had 

 just previously been given by the centralis anterior. 



The right hemisphere in centralis region was then similarly examined, 

 and gave similar results (fig. 5, B). The animal was then killed. 



Examined microscopically, the bulb and spinal cord revealed by the 

 Marchi method the following degenerations (fig. 22) : — The pyramids 

 exhibited large numbers of degenerated fibres distributed fairly symmetri- 

 cally right and left, but distinctly rather less numerous in the right pyramid 

 than in the left. In both pyramids the degenerated fibres were rather less 

 densely scattered in the extreme ventrolateral portion of the cross-section. 



