Reissner's fibre in the rat: a scanning and transmission electron microscope study.

The structure and connexions of Reissner's fibre have been studied in the rat by means of scanning and transmission electron microscopy. The fibre was found to arise from a series of filaments, each of which was formed by a structure forming the juxta-aqueductal surface or lining of the subcommissural organ. This structure was termed 'apical spherical protrusion' and was found to be rich in rough endoplasmic reticulum. The fibre was firmly attached at its rostral end to the subcommissural organ, at its middle to the ventral surface of the termination of the aqueduct and finally to the calamus scriptorius of the fourth ventricle. It was held in a state of considerable tension between these three points and attached to it were numerous cilia from the ependymal lining. In sections examined by TEM the fibre appeared to be totally amorphous in structure, with erythrocytes and other debris attached to it.