- A gritty substance present in central nervous tissue or in the pineal gland.acervulus psammoma body
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
Examples from the Web for brain sand
This pigment is apparently calcium phosphate, which still remains as the 'brain-sand' of the human pineal gland.The Origin of Vertebrates
Walter Holbrook Gaskell
It contains a small quantity of peculiar particles of gritty, sand-like substance, which are sometimes called "brain-sand."Clairvoyance and Occult Powers