Light micrograph showing a sagittal section of a human pineal gland. The sample is from a 69-year-old man. The pineal recess is on the left, opened to the third ventricle and situated between the two commissures. The habenular commissure shows a huge deposit of calcium concretions (corpora arenacea, brain sand). On the contrary, the posterior commissure is free of them. The pineal parenchyma shows a distinct lobulation and some small glial spots.