The unpaired, flat, cone shaped organ, weighing approximately 0.1 - 0.2 g, is to be found leaving the rear wall of the third cerebral ventricle and growing dorsally.
The function of Corpus Pineale is still, even today, heavily disputed.
In lower vertebrata, itīs purpose is that of a light perceptive organ. Under the stimulus of bright light it secretes the hormon melantonin. This causes a conglomeration of skin pigments, resulting a paling of the skin.
One of itīs functions in the human body which is under discussion is:
Co-ordination of the circadian rythym (day and night rythym), a remainder of itīs primary function as a light perception organ.
Hundreds of years ago Corpus Pineale occupied the minds of not only anatomists but also of philosophers.
The great french philosopher, René Descartes, saw in the Pineal Gland the locus of the soul - the place where body and soul influence each other, alternately.
(Theory of alternation)