On the descending degenerations which follow lesions of the gyrus marginalis and gyrus fornicatus in monkeys / by E.P. France ; with an introduction by Professor Schäfer.

  • France, E.P.
Date:
1889
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Licence: Public Domain Mark

Credit: On the descending degenerations which follow lesions of the gyrus marginalis and gyrus fornicatus in monkeys / by E.P. France ; with an introduction by Professor Schäfer. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    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 Ferrter. It was, therefore, only to be expected that we should find 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 spinal 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 ver}' exten- sive removal of the gyrus fornicatus was productive of no muscular 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 (»f conduction and degeneration is the same, be correct, this conclusion of ours would have to be 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, to 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 which would then arise is. What is the nature of these centrifugal impulses % 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 be explained by supposing contraction of cutaneous vessels (and consequent numbness) to result from the removal. But are we bound 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