Anatomy of a new paired tract of the pineal gland in humans.

The human pineal gland and it anterior attachments were investigated grossly in the fresh state and microscopically in the sagittal plane and 25 degrees tangential to the coronal plane of sectioning. Fiber stains of tissue samples from the midline commissural attachments of the pineal gland indicated the presence of both myelinated and non-myelinated fibers connecting the pineal gland and the pre-tectal area. A previously unreported paired fiber tract was observed associated with the anterior inferio-ventro-lateral pineal gland. This paired tract appears to be physically separate and distinct from the posterior commissure. These tracts form a structural component of the wall of the pineal recess. The fibers coursing in this paired tract are myelinated, and are of two different sizes (1-3 microm diameter and 5-8 microm diameter) as determined by electron microscopy. Fibers from these tracts invade the pineal gland, and can be traced a short distance into the lateral pre-tectal area. The precise point of origin and termination for this paired tract is unknown.