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Abstract
The pineal gland is a universal feature of vertebrate organization. In theoretical descriptions formUlated during the I600s, a clock-like role was attributed to the gland and it was egablished the belief that pineal function underlies the laos of the universe that determine the cyclic sleep-awake states in man..
Embryology
The neural tube cranial td the somites develops into the brain. During the fourth week, three primary brain %-esicles form the forebrain or the prosencephalon, the midbrain or the mesencephalon, and the hindbrain, or the thonibencephalon. (figure 1) During the fifth week, the forebrain partly dividos into two vesicles, the telencephalon and the diencephalon, and the tiindbrain partly divides into the metencephalon and the myelenceplialon. Therefore, there are five secondary brain vesicles (figure 2),
Currently, the diencephalon of the developing embryo is considered to contain only the alar component of the neural tube. However, the hypothalamic sulcus, which appear to be a cranial extension of the sulcus limit., was used to divide the diencephalon into the pars.