The glial fascicle: an ontogenic and phylogenic unit guiding, supplying and distributing mammalian cortical neurons.

Neurons destined for the mammalian neocortex migrate along radial glial cells (RGCs). This paper describes a comparative study of RGCs in the mouse, rat, hamster, cat and human fetus, selected as representative species of mammalian evolution. The glial fascicles display constant features throughout these species: they consist of 4-10 RGCs filled with glycogen. The glial fascicle guides and probably supplies metabolites to the migrating neurons and organizes the vertical lamination of the developing neocortical plate. The neuronal-glial unit which consists of the RGCs and their affiliated migrating neurons is conserved throughout the species studied, suggesting a designation as a phylogenic unit.