The pallidonigral set comprises the direct targets of the striatal axons: the two nuclei of the pallidum, and the pars compacta (SNpc) and pars reticulata (SNpr) of the substantia nigra. One character of this ensemble is given by the very dense striato-pallidonigral bundle giving it its whitish aspect (pallidus means pale). In no ways has the pallidum the shape of a globe. After Foix and Nicolesco (1925) and some others, Cécile and Oskar Vogt (1941) suggested the term pallidum - also used by the Terminologia Anatomica (1998). They also proposed the term nigrum for replacing nigra, which is indeed not a substance; but this is generally not followed. The whole pallidonigral set is made up the same neuronal components. The majority is made up of very large neurons, poorly branched, strongly stained for parvalbumin, having very large dendritic arborisations (much larger in primates than in rodents) with straight and thick dendrites. Only the shape and direction of the dendritic arborizations differ between the pallidum and the SN neurons. The pallidal dendritic arborisations are very large flat and disc-shaped. Their principal plane is parallel to the others and also parallel to the lateral border of the pallidum; thus perpendicular to the axis of the afferences. Since the pallidal discs are thin, they are crossed only for a short distance by striatal axons. However, since they are wide, they are crossed by many striatal axons from wide striatal parts. Since they are loose, the chances of contact are not very high. Striatal arborisations, emit perpendicular branches participating in flat bands parallel to the lateral border, which increases the density of synapses in this direction. This is true for not only for the striatal afferent but also for the subthalamic (see below).