LOBES AND GYRI OF THE CONVEX SURFACE. 67 



before backward they are as follows: The supramarginal, the 

 angular and the post-parietal (Figs. 20 and 24). 



The supramarginal gyrus arches over and closes the upturned 

 end of the posterior ramus of the lateral fissure of the cerebrum 

 (Fig. 24). The anterior segment of the arch is continuous with 

 the posterior central gyrus and is comprised in the psychic-sensory 

 area; the posterior segment of the arch fuses with the angular 

 gyrus, behind, and the superior temporal gyrus, below, and 

 belongs to the psychic-sensory area, also, the motor memory center 

 (Fig. 56). 



The angular gyrus forms an arch over the end of the superior 

 temporal sulcus (Figs. 20 and 24). The angular arch is in direct 

 continuity with the superior and middle temporal gyri and the 

 posterior segment of it is continuous with the post-parietal gyrus 

 when that gyrus is present. 



The post-parietal gyrus is present only when the middle 

 temporal sulcus bends upward and terminates in the parietal 

 lobe; in which case this gyrus curves over and closes that sulcus 

 (not figured). It connects the posterior ends of the inferior and 

 middle temporal gyri and also blends with the superior occipital 

 gyrus. The angular, post-parietal and superior occipital gyri on 

 the left side, according to Mills and others, constitute the center 

 for visual memories. The studies of A.' W. Campbell render it 

 probable that the visual cortex does not extend into the parietal 

 lobe of man at all. The receptive visual center for macular vision 

 (vision in the macula lutea of the retina) is likewise located in 

 the angular or post-parietal gyrus by Mills, but it is probably 

 situated on the medial surface of the occipital lobe; unlike the 

 memory center, this is present in both hemispheres. 



(3) Occipital Lobe. (Lobus occipitalis, Figs. 20, 22, 24, 26 

 and 28). The occipital lobe forms the posterior pole of the hem- 

 isphere. With the parietal and temporal lobes it is directly con- 

 tinuous, being marked off from them by an imaginary line drawn 

 from the preoccipital notch to the occipito- parietal sulcus. This 

 sulcus, on the convex surface, bounds it to the extent of about 

 an inch; rarely, the external perpendicular sulcus bounds it in 

 front. On the medial and basal surfaces of the hemisphere the 



