The pineal gland has been a subject of interest and speculation for more than 2000 years. Greek anatomists were impressed by the ob- servation that the pineal gland is an unpaired structure and they believed that it regulated the flow of thoughts. The philosopher Descartes proposed an important role for this organ in brain function. At the beginning of the 20th century experiments by several investi- gators indicated that the pineal influenced sexual function and skin pigmentation and was also responsive to light signals. With the iso- lation of melatonin from bovine pineal glands by Lerner...