332 
MR, E. P. FRANCE ON DEGENERATIONS WHICH FOLLOW LESIONS 
gyras was sufficiently complete in all the cases here selected to produce characteristic 
symptoms and characteristic descending degenerations. 
It may be remembered that the symptoms which were found (by Horsley and 
myself) to follow removal of one marginal gyrus indicated paralysis of the trunk 
muscles and of most of the leg muscles (especially the extensors) of the opposite side 
of the body; double marginal lesion causing a corresponding bilateral paralysis. 
This result was in conformity with our earlier experiments, which demonstrated that 
on electrical excitation of this gyrus movements of the trunk and opposite leg were 
chiefly produced. It showed conclusively that the gyrus marginalis is to be regarded 
as part of the so-called motor region of the brain as mapped out by Ferrier. It 
was, therefore, only to be expected that we should And descending degenerations 
along the course of the pyramidal tract, as is indeed seen to be the case if the 
following account of the degenerations and the photographic representations of 
sections through the sjjinal cord and medulla are referred to. The chief feature of 
interest in this part of the investigation is the localisation of the degeneration mainly 
to the postero-lateral part of the crossed pyramidal tract area of the cord. 
With regard to the gyrus fornicatus, the results of electrical excitation were found 
by us to be negative, so far at least as any movements of muscles were concerned. 
And we also found that, except such slight paresis as might well have been accounted 
for by the unavoidable injury to the adjacent marginal convolution, even very exten¬ 
sive removal of the gyrus fornicatus was productive of no muscuku’ paralysis. On the 
other hand, we obtained well marked deficiency in the general and tactile sensibility 
of the opposite side of the body, and concluded therefrom that this part of the limbic 
lobe was probably concerned with the reception of sensory impressions. 
If the view which is usually held, viz., that in the central nervous system the 
direction of conduction and degeneration is the same, be correct, this conclusion of 
ours would have to he modified, in consideration of the extensive descending 
degenerations along the whole area of the pyramidal tract which are recorded by 
Mr. France as resulting from the lesions of the gyrus fornicatus, for it would be 
difficult, with these facts before us, t.o arrive at any conclusion other than that 
centrifugal nervous impulses emanate from the cells of this gyrus, and pass down 
along the course of the motor tract. 
The question wliich would then arise is. What is the nature of these centrifugal 
impulses I The observations already referred to would seem to show that they do 
not pass to the skeletal muscles, and the idea suggests itself that they are of vaso¬ 
motor (? inhibitory) character. Such a supposition is not at variance with the hemi- 
anmsthetic results obtained on removal of the gyrus fornicatus, for these results 
might he explained by supposing contraction of cutaneous vessels (and consequent 
numbness) to result from the removal. 
But are we hound to accept the above view regarding conduction and degeneration 
in the central nervous system ? It by no means follows that we are. The only law of 
