INTRODUCTION Throughout history, the special anatomical location of the pineal gland in the central nervous system has given rise to a number of physiological hypotheses regarding the functional role of this organ. DEVELOPMENT. In classical ancient times, the pineal body (conarium) was considered to be a sort of valve-like sphincter that regulated the flow of the spiritus animalis at the ventricular level. But it was not until the 17th century that the pineal gland finally reached its highest levels of physiological significance, when Rene Descartes considered it to be the anatomical structure that housed the seat of the soul.

CONCLUSIONS The Cartesian hypotheses regarding the pineal gland did not arouse much interest in the scientific community of the time, and attention to this organ dwindled from then until the 20th century, when its neuroendocrinological nature was finally confirmed.