Comparative Anatomy and Histology of Elephant, Human, and Tree Shrew Brains

OBJECTIVE This study was designed to compare elephant brain mor-phology and histology with that of humans and tree shrews.METHODS The size of elephant, human, and tree shrew brains were measured. Brains were sectioned and stained by the modified Mulligans for investigation of the ratios of gray matter and brain volume. The prefrontal gyrus and cerebellum were Nissl stained. The elephant cere-bellum was prepared for Golgi staining.RESULTS The gyrification of the elephant cerebrum was found to be like similar to that of the human brain, but the gyrification of the tree shrew was not determined. The ratio of gray matter and brain volume of the elephant was less than that of both human and tree shrew brains. However, the olfactory bulbs and cerebellum of both the elephant and tree shrew were large. The cortical layers I-VI of the prefrontal cortex in both elephants and humans did not show a distinct layer IV. Ad-ditionally, elephant cortical neurons were larger than those found in humans. Purkinje neurons in the elephant cerebellum were uniquely shaped, having two main dendrites extending from the cell body.CONCLUSIONS The elephant brain gyrification is similar to the human brain. However, it has large olfactory bulbs and cerebellum as does the tree shrew brain. The cortical and Purkinje cells in elephants are larger and more dendritically branched than those of humans.