[Morphological study of the pineal organ in the spined rat Proechimys iheringi Thomas, 1911].

The pineal organ of the spined rat is located deeply near the third ventricle. The organ shows a compact pattern of organization with pinealocytes and astrocytes arranged in cords and rosettes. Numerous concretions positive to chrome alum hematoxylin technic are visualized in the adjacent tissue near the pineal organ and in the vicinity of the veins which drain the blood of the organ. In the present work we discuss the probable origin of these concretions.