The following is from Mosby's Comprehensive Review (11th ed.):
Pineal Glan
A. Anatomy
1. A firm, reddish, conical (pine conical, hence the name) structure lying in
the midbrain between the superior colliculi and attached by a short stalk to
the roof of the third ventricle
2. Composed of cords of pinealocytes (or chief cells) separated by connective
tissue; septa continuous with the pia mater covering the organ; cells
accumulate calcareous granules (brain sand) by age 18 clearly visible at x-ray
examination
B. Actions of pineal hormone
1. Secretes melatonin
2. Melatonin may regulate diurnal fluctuations of hypothalmic-hypophyseal
hormones
I hope this gives the details you wanted concerning the pineal's composition.
At least now we know to what the 'grains of golden sand' in the original
hypocratic oath refer.
Regards,
JC Snooky