Section through the mid-brain at the level of the superior corpora quadrigemina (SG). The latter, it should be noted, show a somewhat stratified structure - with alternate layers of grey and white matter. One fairly well marked layer of medullated fibres is made up of the terminal fibres of the mesencephalic root of the optic tract and is called the stratum opticum (SO). These fibres are conveyed to the superior corpus quadrigeminum by the superior brachium (SB). Note the termination of the optic tract (OT) in the lateral geniculate (LG), and the laminated structure of the latter. Above the lateral geniculate body is the pulvinar (Pulv), and medially the medial geniculate body (MG) which receives the termination of the auditory fibres of the lateral fillet. These fibres are conveyed in the inferior brachium which is seen on the left side of the section (IB). Note the well-defined red nucleus (R), flanked on its lateral aspect by the medial fillet (Mf) on its way up to the thalamus. The cerebral peduncle (CP), the substantia nigra (Sn), and the roots of the oculo-motor nerve (III) should be identified. The oculo-motor nucleus is situated in the floor of the aqueduct (Aq).

Original card