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The Structure of the Cerebral Hemisphere

Published online by Cambridge University Press:  19 February 2018

W. H. Broadbent
W. H. Broadbent*
Affiliation:
St. Mary's Hospital Medical School, &c
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Extract

The dissections on which the following account of the structure of the cerebral hemisphere is founded, have been described in detail in a communication to the Royal Society. The results will be here given, without regard to the order in which they are reached, and with a view simply to clearness and comprehensibility.

Type
Part I.—Original Articles
Information
Journal of Mental Science , Volume 16 , Issue 73 , April 1870 , pp. 1 - 24
Copyright
Copyright © Royal College of Psychiatrists, 1870

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References

∗ The relations of the optic tract with the thalamus and other parts are suffi ciently interesting to be worthy of a brief note. Following it from the commis sure backwards, it is first found that the commissure is very closely adherent to the tuber cinereum, and cannot be detached without breach of structure. Usually the commissure raises fibres which belong to the tuber cinereum. As the tract is traced backwards, its outer edge is seen to be joined by fibres from the groove in which it is lodged. On reaching the anterior pointed extremity of the extra-ventricular part of the thalamus, it is not difficult to raise it with the tract, but if the tract is kept distinct from the fibres which do not strictly form part of it, it suddenly detaches itself from the thalamus, raising a small, solid, firm, grey nucleus about the size of a barley corn from a smooth bed, in which it was lodged, with scarcely any rupture of fibres. It is evident that the mass of the fibres of the tract end in this nucleus, but a distinct though slender tract of fibres is continued onwards to the corpora quadrigemina; others again pass to the C. geuiculatum internum, which is seated on the posterior edge of the tegmentum of the crus, some of these dipping into the groove between the crust and tegment.Google Scholar

∗ It will be seen that the short ascending branch of the fissure of Sylvius is taken as the line of separation between the frontal and parietal lobes. The fissure of Rolando, though appearing early, is a mere sulcus, and the small contorted horizontal gyri, and the larger and simpler ascending gyri seem to fall naturally into distinct groups.Google Scholar

∗ Confirmation of this is readily found in a comparison of the hemisphere of the monkey tribe with that of man, material for which is furnished by Gratiolet's work on the cerebral convolutions in the primates and man. I have not had the opportunity of examining a monkey's brain, but by the kindness of Mr. Streeter I have before me a cast of one, which may be taken as a sample, the convolutions being very simple. The frontal lobo is represented by a superior and inferior gyrus, the second being rudimentary; the parietal has a simple as cending convolution on each side of the sulcug of Rolando, and a supra-marginal sylvian gyrus. No supra marginal or postero-parietal lobule. The occipital lobo is plain; the temporo-sphenoidal, large in proportion to the restofthe hemisphere, has infra-marginal, parallel and uncinate gyri, no superadded gyri, on the under surface. To bring this into the likeness of a human brain it would be necessary to interpose a second frontal gyrus between the first and third, to add supra-marginal and postero-parietal lobules, to replace the smooth surface of the occipital lobe by numerous and tortuous convolutions connected with the rest of the hemisphere by annectent convolutions, and to increase the complexity of the callosal and marginal gyri, and of the gyri on the orbitar lobule, and on the under surface of the temporo sphenoidal lobe.Google Scholar

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