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.

    6/10 (page 288)
    present; but this much I may say, viz., that the chief diflference to be noted in this region between human and anthropoid brains is, that in the latter there is no undermining of this convolution by the island of Reil in front of its pars basilaris. But, further, another very striking difference between the human cerebrum and the anthropoid cerebrum is to be found in the relative size and in the position of the island of Reil. If we take the length of the lateral surface of the hemisphere as being equal to 100, the average length of the insula in the European is 29'6; in the Negro, 28'3 ; in the Orang, 21 o; and in the Chimpanzee, 182. Hefiftler, Guldberg, and Eberstaller have pointed out that in man the island of Reil is divided by a well-marked furrow, termed the sulcus centralis, which has the same direction, and lies in the same plane as the fissure of Rolando, into a fore part or pars frontalis, and into a posterior portion or pars temporo-parietalis. The pars frontalis is the larger of the two, and is connected solely with the frontal lobe. The pars temporo-parietalis is con- nected with the parietal and temporal lobes. In the anthropoid ape, if there is any part of the pars frontalis present, it is merely that portion of it which Eberstaller terms the gyrus tertius. It is extraordinary that in the lower apes the island of Reil should present a greater antero-posterior diameter than in the anthropoid apes. In the Macaque it is 24-9; Hamadryas, 23'9 ; Baboon, 27-9 ; Mangaby, 25-3 ; Cebus, 25-5. In the human brain, if we consider the lateral length of the hemisphere to be 100, the length of the frontal operculum is 6-9, and from the period of its full development in the first year of life up to the adult condition, it does not vary. On the left side, however, it is longer than on the right side, in the proportion of 8 to 6-1. Further, it appears to be shorter in the Negro than in the European. Topography of the Sylvian Fissure.—The point at which the trunk of the Sylvian fissure appears on the outer face of the hemisphere may be termed the Sylvian point. The position of this in the human brain varies somewhat at different periods of growth. It makes a slight advance in a forward direction as growth progresses, and it may be said to become finally fixed in its position about the eleventh year. In the adult male it is