_Nervous system._--In this part of the organism we are especially interested in the structure of the brain. Bastian justly remarks, with reference to the brain of apes, that this family possesses many cerebral characteristics in common, by which their close connection with each other may be verified. Distinct stages of development have been observed, which, however, cannot be classified in a consecutive series. Starting from the brains of lemurs, which do not greatly differ from those of rodents, we can advance by means of very distinct transition forms to the more highly developed cerebral hemispheres of the large anthropoid apes, the chimpanzee, the gorilla, and orang-utan.[80] [Illustration: Fig. 57.--Brain of the chimpanzee, seen from above. The upper part of the right hemisphere is removed so as to lay bare the lateral ventricle (Vogt, from Marshall). L, Longitudinal fissure (other indications the same as in Fig. 56). _c s_, The corpus striatum in anterior cornu of the ventricle. _c a_, Hippocampus major in descending cornu. _h m_, Hippocampus minor in posterior cornu. ] Very opposite views prevail among anatomists with regard to the question which species of anthropoids possesses the most highly developed brain. Some regard the chimpanzee’s brain as the simplest, and that of the orang as the most highly developed. In all these apes the lateral halves of the cerebrum, always divided from each other by a deep longitudinal fissure, overlap the cerebellum as far as a minute posterior segment. In this respect I find the brain of the gorilla a little behind the other anthropoids. Up to this time, I have only observed the projection of the cerebellum through the cerebrum in the case of an orang[81] (see also Fig. 56). Retzius asserts that the cerebellum of Lapps is incompletely covered, while the covering is generally complete in the case of Slav and Tartar races. In German and Latin races the cerebrum overlaps the cerebellum. In Mongolian, Indian, and Negro races the covering appears to be generally imperfect. [Illustration: Fig. 58.--Brain of gorilla, side view (from Bolau and Pansch). I., Frontal lobe. II., Fissure of Rolando. III., Parietal lobe. IV., Temporal lobe. C, Cerebellum. _f s_, Fissure of Sylvius. _s c_, External fissure parieto-occipital. ] While the ground form of the gorilla brain approximates to a long oval, and in this respect resembles the human brain, the brain of chimpanzees and orangs is of a round-oval form. This is especially the case with the chimpanzee (Fig. 57). In my opinion, the gorilla brain is distinguished from that of the chimpanzee, but not from that of the orang, by its very complex convolutions (Fig. 56). [Illustration: Fig. 59.--Brain of orang, seen from above (Duncan, from a specimen in the Museum of Royal College of Surgeons). F, frontal lobe. O, Occipital lobe. ]