The function of the collicular bodies of the quadrigeminal plate in man, and particularly that of the superior (or anterior) colliculi, remains undetermined. Not only has little experimental work been devoted to the problem, but little suitable human material has been available for study. The case which will be reported here seems ideal in many respects, and we feel that its presentation is worth while. COMPARATIVE ANATOMY AND PHYSIOLOGY OF THE COLLICULI Studies in evolution show that the function and importance of the tectum mesencephali have been steadily regressive.1In the very early vertebrates, such as the bony fishes, the tectum consists of a relatively large bilobular body situated on the alar plates that cover the aqueduct. These corpora bigemina (in selaceans) are exclusively visual in function. The expanded portion of the alar plates serves as the end station of the somesthetic pathway. Beginning with the amphibians and progressing