The Sylvian fissure and the island of Reil in the human brain / by D.J. Cunningham.

  • Cunningham, D. J. (Daniel John), 1850-1909.
Date:
[1891?]
Catalogue details

Licence: Public Domain Mark

Credit: The Sylvian fissure and the island of Reil in the human brain / by D.J. Cunningham. 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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    operculum. These have previously been noted by Eberstaller, whilst Zuckerkandl has observed the outer of the two. The four anterior limbs are not constant in their relations or presence. No less than fifteen different combinations occur. In the Negro brain there appears to be a deficiency in the orbital operculum; and the anterior orbital limbs of the Sylvian fissure which incise it are less frequently present than in the European brain. One of the most remarkable characters in the cerebrum of the Oraug and the Chimpanzee is the total absence of the frontal and orbital opercula. The temporal and parieto-frontal oper- cula are alone present. There is a so-called anterior limb of the Sylvian fissure, but it hardly comes within the definition that we have given of an anterior limb. It bounds the parieto-frontal operculum in fi-ont, it is true, and the fore-border of this operculum forms its superficial wall. It cuts into the hemisphere very obliquely, and the surface of its deep wall is carried almost continuously into the surface of the island of Reil. It is curious that while the anthropoid should be so absolutely destitute of a frontal and an orbital operculum, there are many of the lower apes {e.g. Baboons, Macaques, &c., &c.,) which show a faint trace of the orbital operculum. But it may be asked why we have so decidedly stated that the frontal operculum (pars triangularis) is absent in anthropoids, seeing that we might very well suppose that it was merely fused with the fore part of the parieto-frontal operculum. This is no doubt the view of those who hold that the so-called anterior limb of the Sylvian fissure is homologous with the anterior horizontal limb in man, but it is an erroneous supposition. The fact is, that if we are to regard this anterior limb of the Sylvian fissure in the anthropoid brain as homologous with anything, it must be with the ascending limb of the human brain, and for this reason: the pa/rt of the island of Reil which corresponds to the frvfdol orpercvhj/m or pars triangularis in man is absent in the anthropoid ape. There has been a great deal of discussion upon the third frontal convolution, and its deficiency or absence in the Ape. This is a question into which I am not prepared to enter at