The birth of oligodendrocytes in the anatomical and neuropathological literature: the seminal contribution of Pio del Rio-Hortega

Comment on: del Rio-Hortega P Glia with very few processes (oligodendroglia). Clin Neuropathol. 2012; 31: 440-459, originally published in Archivos de Neurobiologia. 1921; 2: 16-43 and del Rio-Hortega P Are the glia with very few processes homologous with Schwann cells? Clin Neuropathol. 2012; 31: 460-462, originally published in Bol de la Soc Esp de Biol. 1922; X: 25-28.