LOBES AND GYRI OF THE CONVEX SURFACE. 7 1 



the basal surface, runs interruptedly close to the infero-lateral 

 border of the hemisphere and parallel with it (Fig. 26). It sep- 

 arates the inferior temporal gyms from the fusiform gyrus. 



The superior temporal, the middle temporal and the inferior 

 temporal gyri are of nearly equal width (Figs. 24 and 26). They 

 fuse with one another and with the fusiform gyrus at the temporal 

 pole. The superior temporal gyrus is continuous with the supra- 

 marginal and angular gyri, posteriorly: in its third and fourth 

 fifths and in the transverse temporal gyri is the receptive auditory 

 center (Barker). 



The middle temporal gyrus fuses at its posterior end with 

 the angular gyrus and either with the post-parietal or the superior 

 occipital. Along the superior temporal sulcus, in the middle 

 two- fourths of the superior and middle temporal gyri is the center 

 for auditory memories, the psychic auditory center. This center 

 is in the left hemisphere of right handed people (Figs. 54 and 56). 



The inferior temporal gyrus forms the infero-lateral border 

 of the hemisphere (Figs. 24 and 26). It is continuous with the 

 lateral occipital gyrus and sometimes, also, with the superior 

 occipital and post-parietal gyri. If this gyrus and the lower 

 half of the middle temporal gyrus be divided into four equal parts, 

 each fourth, according to Mills, belongs to a definite center. 

 From behind forward they are the center of orientation; the center 

 of equilibration (?); the naming center; and, in the anterior fourth 

 and the pole of the temporal lobe, the center of intonation (Fig. 56). 



(5) The island (insula, Reili) is also called the central lobe 

 (Figs. 25, 26, 31 and 36). It is situated in the medial wall of 

 the lateral fissure of the cerebrum, between the frontal, parietal 

 and temporal lobes, whose growth, after the fifth month in utero, 

 gradually covers it over. At the end of the first year of extrauterine 

 life it is entirely concealed by temporal, parietal, and frontal 

 parts of the operculum. The island is thus separated from the 

 general surface of the cerebral hemisphere by a distance of half 

 or three-quarters of an inch. It is triangular in shape. Its 

 apex is directed downward and forward toward the fossa lateralis 

 cerebri, and is called the pole (polus insula). If the lips of the 

 lateral fissure be widely separated, the sulcus circularis insulae 



