brain sand n.
A gritty substance present in central nervous tissue or in the pineal gland. Also called acervulus, psammoma body.
It contains amylaceous and gritty, calcareous particles constituting the brain sand.
It contains a small quantity of peculiar particles of a gritty, sand-like substance, which is commonly known as "brain sand."
In its structure this body consists of tubular gland tissue containing gritty calcareous particles, constituting the brain sand.