Bischoff asserts that the third frontal convolution (Broca’s convolution) is very slightly developed in the chimpanzee, orang, and gibbon. “Its great development in men,” Gewährsmann writes, “constitutes one of the most marked distinctions between the brains of apes and of men.”[83] In most of the other species of apes this convolution is altogether absent, but Pansch is justified in the assertion that it is fully developed in anthropoids. I cannot wholly agree with Pansch in his analysis; but I must accept his statement on this point (see the orang, Fig. 59). Gratiolet remarks that the so-called annectant gyri (_plis de passage_) which serve as a covering or _operculum_ for the posterior lobes in apes, are only superficially apparent in man. In the chimpanzee the upper of those convolutions is absent, while it is large in the orang, and likewise large and undulated in man. In the orang the second annectant gyrus is covered, but this covering is absent in man.[84] In considering the inner structure of the brain of these animals, we are first struck by the shortness of the _corpus callosum_. The soft and thick anterior commissure of the third cerebral ventricle and the thin posterior commissure have also been justly noted. In the lateral ventricles more of the characteristics described in the human brain are absent. The four eminences resemble those of man; nor does the fourth cerebral ventricle present any remarkable differences of form. Neither does the base or lower surface of the brain display any important deviation from the human type. The transverse section of the nerves at their intersection appears to me, however, to be somewhat more oval than is the case in man.