352 
MR. E. P. FRANCE ON DEGENERATIONS WHICH FOLLOW LESIONS 
the whole motor area was removed ; whilst in those where only the external motor 
area was involved a part along the posterior mesial border appears less completely 
degenerated than the rest (diagrams 5 and 6). 
Diagram 5. Diagram 6. 
Degeneration in the pyramid of the medulla following Degeneration following lesions of the 
lesions of the external motor area. entire motor area. 
In the spinal cord the degeneration occupies the whole extent of the crossed 
pyramidal tract in those cases where the whole motor area was removed; but where 
only the external motor area was involved, that part of the pyramidal tract bordejing on 
the direct cerebellar tract is less degenerated, though never quite free from degeneration. 
This fits in with what I have said of t,he degeneration following marginal lesions, 
which chiefly occupies the part bordering on the direct cerebellar tract. 
In the cervical region, the degeneration besides occupying a position corresponding 
to that seen in the dorsal region, also extends as a narrow band along the circumfer¬ 
ence towards the posterior root exit (diagr. 7), but there is always a well-marked 
tract of healthy fibres (direct cerebellai' tract) close to the posterior root exit, extending 
into and separating the degeneration in the crossed pyramidal tract proper from the 
band extending along the circumference. 
Diagram 7. 
The deg£'nei ation as seen in the upper cervical region showing the direct cerebellar tract 
enclosed by degenerated crossed pyramidal tract. 
Diagram 8. 
Showing the degeneration at the level of the sixth dorsal nerve. 
In the dorsal (diagr. 8) and lumbar regions no constant difterence in shape and 
position can be made out between the degeneration following removal of the external 
motor surface, and removal of the entire motor area. 
It gradually diminishes as it descends, but can be seen in the lumbar region (at the 
level of the 3rd or 4th nerve) as an oval patch close to the circumference and near the 
pfosterior root exit. 
I have never in any case in the Monkey observed degeneiation in the anterior 
columns of the spinal cord, and conclude, therefore, that in these animals the 
pyramidal decussation in the medulla oblongata is compdete. 
