Journal of the Academy of Natural Sciences of Philadelphia . on fig. 5, PlateXXXVII, it will be seen that onthe mesial surface this symmetri-cally developed posterior extremi-ty of the hemisphere is related in a regular and definite manner to the occipito-frontaland occipito-temporal lobes. In this brain of Macacus nemestrinus the fissures havebeen opened up in order to display more perfectly the symmetry of this region, and itcan be at once seen that the occipital lobe is symmetrically folded around the positionof the fissura calcarina, which corresponds to the position of the eminence foundw
Journal of the Academy of Natural Sciences of Philadelphia . on fig. 5, PlateXXXVII, it will be seen that onthe mesial surface this symmetri-cally developed posterior extremi-ty of the hemisphere is related in a regular and definite manner to the occipito-frontaland occipito-temporal lobes. In this brain of Macacus nemestrinus the fissures havebeen opened up in order to display more perfectly the symmetry of this region, and itcan be at once seen that the occipital lobe is symmetrically folded around the positionof the fissura calcarina, which corresponds to the position of the eminence foundwithin the posterior horn of the lateral ventricle known as the hippocampus the position of the two extremities of the transverse calcarine fissure, boththe primary and secondary arches pass in a scroll or spiral-like turn forward towardthe apex of the occipital lobe, the ends of the primary arch being separated from eachother on the lateral surface by the small gyrus, x, (see fig. 20) or 4 (see plates), the 41 JOUEN. A. N. S. PHILA., VOL. X. mof. mot 328 MORPHOLOGY OF THE CEREBRAL CONVOLUTIONS. troisihne pli de passage externe. The secondary arch runs parallel with the first,and as this arch becomes successively more and more tortuous, the secondary alsoincreases in complexity. On the right side of fig. 20 can be seen the primitive rela-tions of the mesial surface of the occipito-frontal and temporal lobes to the fissuresof the occipital lobe, as explained in our previous discussion of this portion of thehemisphere. The morphological plan of the occipital lobe is here expressed in itssimplest condition, and it now remains for us to show the various modificationsthat take place as we advance from the lowest to the highest Primate brains. In the Lemuridse the occipital lobe is entirely smooth. The superior occipitalfissure, O1, is, however, present, as may be seen in Lemur nigrifrons, PlateXXXIV, figs. 16 and 17, also in Propithecus, Plate XXXIV, figs. 14 and 23, inAva
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