The lateral occipital gyrus (Figs. 20 and 28) lies below the lateral occipital sulcus and extends from the occipital pole forward along the infero-lateral border of the hemisphere to the preoccipital notch. Sometimes it is divided into two lateral gyri by an inferior lateral sulcus. It is continuous with the inferior temporal gyrus, except rarely, when the two are sepa rated by the anterior occipital sulcus.
The superior occipital gyrus forms the upper half of the convex surface of the lobe (Figs. 20 and 28). It is incompletely separated from the lateral occipital gyrus by the lateral occipital sulcus and is often divided into two gyri. It is continuous with the post-parietal gyrus around the lateral end of the transverse -occipital sulcus; and, around the medial end of that sulcus, it is joined to the superior parietal lobule by the arcus occipito parieatlis. The latter is a sharply curved annectant gyrus which bounds the occipito-parietal sulcus. When the middle temporal sulcus does not turn upward at its posterior end and terminate in the parietal lobe, the superior occipital gyrus is continuous in front with the middle temporal and angular gyri. As already mentioned, the superior occipital gyrus, according to Mills, belongs to the center for visual memories.
4. The temporal lobe (lobus temporalis, Figs. 20, 26, 27, 28, 3o and 31) is that part of the cerebral hemisphere behind the main stem and helow the posterior limb of the lateral cerebral fissure. It rests in the middle fossa of the skull; forms the temporal pole of the hemisphere; and is continuous posteriorly with the occipital and parietal lobes, from which it is marked off only by the imaginary lines already described. On the basal surface of the hemisphere, the temporal lobe along its medial border is separated from the limbic lobe by the collateral fissure and by a short furrow, which is shallow in the adult human brain, called the sulcus ecto-rhinalis. The temporal lobe is attached to the hemisphere posteriorly and medially; but it presents three free surfaces—a superior, a lateral and an in ferior—which meet at the anterior point, called the temporal pole. The polar region is incompletely separated from the temporal gyri by the crescentic anterior temporal sulcus, when that is present.
The superior surface of the temporal lobe forms the inferior wall of the lateral cerebral fissure (Fig. 3o). It looks somewhat medianward toward the island and constitutes the temporal part of the operculum. It presents a long oblique gyrus and two or three transverse gyri, separated by shallow grooves. The long oblique gyrus is adjacent to the gyrus longus of the island, the sulcus circularis intervening between them; it is continuous anteriorly with the superior temporal gyrus; posteriorly it re cedes from the convex surface and is connected with it only by the transverse temporal gyri of Heschl (gyri temporales trans versi), which abut against the oblique gyrus at an acute angle. These transverse gyri belong to the receptive auditory center (Figs. 38, 46, 47 and 74).
The external surface of the temporal lobe presents the fol lowing sulci and gyri (Figs. 27 and 28): Superior temporal (s. temporalis superior) Sulci Middle temporal (s. temporalis medius) Inferior temporal (s. temporalis inferior). This is really on the inferior surface of the lobe.
Superior temporal (g. temporalis superior) Gyri Middle temporal (g. temporalis medius) Inferior temporal (g. temporalis inferior).
The superior temporal and middle temporal sulci (Fig. 27) di vide the external surface into three nearly equal gyri; they run parallel with each other, with the infero-lateral border and with the lateral cerebral fissure. The superior temporal sulcus, like the lateral fissure, bends upward at its posterior extremity; as sulcus angularis, it terminates in the concavity of the angular gyrus. The middle temporal sulcus is usually an interrupted one. It may present an upward curve at its posterior end which is bounded and closed by the post-parietal gyrus; or it may con tinue in its original direction toward the occipital lobe.
The inferior temporal sulcus, situated in the tentorial area of the basal surface, runs interruptedly close to the infero-lateral border of the hemisphere and parallel with it (Fig. 31). It sepa rates the inferior temporal gyrus from the fusiform gyrus.