In the experimental investigation of certain diseases of the nervous system occurring in human beings, primates have been the favorite laboratory animals, for their close phylogenetic relationship to man and the morphologic similarity of their tissues render the interpretations of the induced lesions clearer and make deductions drawn therefrom more probable. A study of the neuropathologic anatomy of monkeys and apes seemed therefore of interest, not only to the comparative pathologist, but also to the experimental neurologist; for a knowledge of the spontaneous lesions that may occur in such animals may prevent misinterpretation of changes found after an experiment. Through the kindness of Dr. Herbert Fox, the director of the Laboratory of Comparative Zoology of the Philadelphia Zoological Garden, a number of brains from primates which had died at the garden were made available. The organs were hardened in formaldehyd and sections taken routinely from various portions of the cortex