The fissure of Rolando / by D.J. Cunningham.

  • Cunningham, D. J. (Daniel John), 1850-1909.
Date:
[1890]
Catalogue details

Licence: Public Domain Mark

Credit: The fissure of Rolando / 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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    present, and it is almost always seen turning round the lower border of the operculum below the lower end of the fissure of Eolando fPl. I. fig. 7, a.). I believe that where the union between the fissure of Rolando and the inferior transverse sulcus takes place, it usually leads to a direct connection between the former and the fissure of Sylvius. In only four cases have I seen the deep annectant gyrus crossing the bottom of the lower end of the fissure of Rolando without such a connection being established. In the Chimpanzee the deep annectant gyrus in the lower part of the fissure of Rolando, which indicates a union with the inferior transverse furrow, appears to be usually present. In only one out of four hemispheres in my possession is it absent. In the other three it is strongly marked, and in one of these there is a superficial con- nection between the fissure of Rolando and the fissure of Sylvius. Even in that hemisphere, in which there is no trace of the deep annectant gyrus, it appears likely that a fusion between the fissure of Rolando and the inferior transverse furrow has taken place, because the sulcus is not any shorter and it reaches as low down as in the case of the other hemispheres. The union, however, is of a more complete kind. In the Orang, also, I find in two hemispheres a very distinct deep annectant gyrus crossing the bottom of the inferior part of the fissure of Rolando, and partially cutting off a small portion w'hich probably represents Eberstaller’s inferior transverse furrow. When I deal with the development of the fissure of Rolando I shaU again have occasion to allude to this deep annectant gyrus, and to point out its importance from a morphological point of view% Between its two exti’emities the fissure of Rolando pursues a sinuous course. Very seldom in the adult brain is it quite straight. As Eberstaller and others have shown, two of the bends, termed respectively the superior and inferior genua, are more conspicuous than the others. In typical cases these are placed at an equal dis- tance from each other and from the two ends of the sulcus, so that they mark it out into three equal parts. The superior genu is usually much the weaker of the two and is directed backw'ards. The upper third of the fissure inclines downwai-ds and slightly backwards. At the superior genu the sulcus bends suddenly in a forward and downward direction. The inferior genu is always strongly marked and looks forwards. Here the fissure again changes its direction and proceeds very nearly vertically downwards. In almost every case the educated eye is able to detect these genua. Perhaps the most common deviation from the condition which we have described as being typical is one in which the central piece of the fissure of Rolando becomes considerably shortened mid nearly horizontal in its direction. The twm genua are thus more closely approximated, and the inferior may lie almost directly in front of the superior. We have seen that when the lips of the fissure of Rolando are drawn widely asunder, a deep annectant gyrus is sometimes seen in