Diseases of the nervous system / edited by Archibald Church.

Date:
1908
Catalogue details

Licence: In copyright

Credit: Diseases of the nervous system / edited by Archibald Church. Source: Wellcome Collection.

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    the sulcus frontalis superior and sulcus frontalis inferior, both of which run anteriorly from the sulcus praecentralis toward the median border of the hemi- sphere. The many smaller fissures, some of which are not invariably found, will not be enumerated. These fissures form four convolutions: (1) The gyrus centralis anterior, lying between the central fossae, the sulcus praecen- tralis, and the Sylvian fissure; (2) The gyrus frontalis superior (first frontal convolution) between the sulcus praecentralis, sulcus frontalis superior, and median border of the hemisphere, and extending above the latter to the median surface of the hemisphere; (3) The gyrus frontalis medius between the upper and lower frontal fissures; (4) The gyrus frontalis inferior, known as the third or Broca’s frontal convolution, and so designated by Broca, but pre- viously described by Gall; Broca, however, first definitely recognized it as the seat of the motor speech function. This is divided by the ramus anterior verticalis and the ramus anterior horizontalis of the Sylvian fossa into the pars opercularis, the pars triangularis, and the pars orbitalis; the latter ex- tends to the orbital surface jof the frontal lobe, as also the two other frontal convolutions. Here the inconstant fissures, such as the sulcus cruciatus orbi- talis and, extending medially from it, the sulcus olfactorius, are included; the latter receives the tractus olfactorius. The parietal lobe with its lateral and medial surfaces has but one typical fissure, the sulcus interparietalis, which rises immediately above and parallel with the Sylvian fossa, behind the sulcus centralis, and forms an arch behind the occipital lobes. A small branch of this sulcus, which extends upward to a greater extent than and parallel with the central fissure, is called the sulcus retro centralis. Here are formed the following convolutions: (1) The gyrus centralis posterior behind the central fissure; above this and upon the median surface of the hemisphere it enters the paracentral lobe and unites with the gyrus centralis anterior; below it enters the central fossa and joins the oper- culum above the Sylvian fossa. This convolution is much narrower than the anterior central, from which, according to the investigations of Ramon y Cajal, it differs decidedly in its finer structure; (2) the gyrus parietalis superior (the upper parietal convolution) behind the gyrus centralis posterior and above the sulcus interparietalis, with the precuneus at the medial sur- face of the hemisphere; (3) the gyrus parietalis inferior (lower parietal lobe) is divided below the sulcus interparietalis into gvrii, the gyrus supramargi- nalis and the gyrus angularis, of which the former surrounds the posterior end of the Sylvian fossa, while the pli courbe, much discussed in scientific com- bats as the gyrus angularis and the cortical center of sight, surrounds the posterior portion of the sulcus temporalis superior, and is therefore not sharply separated from the occipital lobes. The occipital lobe has the form of a triangle with its base upon the parie- tal and temporal lobes while its apex points backward; it is called the occipital pole. Corresponding to this is a frontal pole upon the most anterior portion of the frontal lobe. Fossae are not always found on the lateral surface of the occipital lobe. As a rule, the main furrows are the sulcus occipitalis trans- versus which is situated transversely behind the interparietal fissure and runs through that area in which we find in monkeys a deep space separating the posterior and parietal lobes, the sulcus occipitalis lateralis, situated in the lower part of the occipital lobe and running close to the posterior pole, and a
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