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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    sulcus occipitalis anterior in the anterior portion of the occipital lobe near the extension of the posterior ascending part of the sulcus temporalis medius. The difference in these furrows accounts for the varied formation of three convolutions upon the lateral surface, which like the three frontal convolutions extend from before backward as an upper, middle and lower gyrus occipitalis. Each of these convolutions passes forward uninterruptedly into another con- volution, the upper into the gyrus parietalis superior, the middle into the gyrus angularis, and the lower into the middle temporal convolution. Before describing the median division of the occipital lobe, we must first consider the temporal lobe which occupies the lowest part of the cerebral hemisphere, and is limited anteriorly and above by the Sylvian fissure, while posteriorly it passes into the parietal and occipital lobes without a sharply de- fined limitation. Here, following each other from above downward and run- ning parallel with the Sylvian fossa, are the sulcus temporalis superior, a part of which ends with the gyrus angularis, and which has also an anterior horizontal and a posterior ascending portion, the sulcus temporalis medius, a less developed one, the sulcus temporalis inferior which extends along the lower surface of the hemisphere, and the sulcus occipito-temporalis inferior. Here are also three convolutions upon the lateral surface, the gyrus temporalis superior which forms the lower boundary of the Sylvian fossa and upon whose surface externally a few invisible gyrii temporalis transversi extend to the island, a gyrus temporalis medius and inferior, the latter partly upon the lower surface of the hemisphere, and wholly upon the latter the gyrus occipito- temporalis lateralis or gyrus fusiformis, lying between the sulcus temporalis inferior and the occipito-temporalis inferior which to a great extent forms posteriorly the basal surface of the occipital lobe; finally, the gyrus occipito- temporalis medialis or gyrus lingualis which is situated between the sulcus occipito-temporalis inferior and the fissura calcarina previously described as one of the main fissures on the median and lower surface of the hemisphere, and which lies almost entirely within the occipital lobe. Anteriorly it passes into the gyrus hippocampi which will shortly be described. In viewing that portion of the medial surface of the hemisphere which has not yet been considered we see the gyrus fornicatus passing from before backward around the arc-like corpus callosum. The upper portion, situated upon the corpus callosum, is called the gyrus cinguli, the lower, bordering upon the temporal lobe, the gyrus hippocampi; these are united upon the pos- terior portion of the corpus callosum by the narrow isthmus—gyri fornicati. The anterior portion of the gyrus hippocampi shows a marked thickening and curvature, the uncus, which must be considered as being within the ante- rior portion of the temporal lobe, and which is analogous to a process in the interior of the ventricle, the cornu ammonis. Corresponding to these con- volutions, and above the corpus callosum, we note the sulcus corporis callosi as the upper limit of the gyrus hippocampi, the fissura hippocampi, which joins the fascia dentata and the nervi Lancisii in man, apparently being em- bryonic convolutions which pass into the lower horn of the lateral ventricles. An important fossa is the sulcus calloso-marginalis or sulcus cinguli, which extends as an arch above the cingulum posteriorly from the genu of the corpus callosum, and passes upward over the splenium of the corpus callosum and immediately behind the central fossa into the lateral surface of the hemi-
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