1. 1 Brief History The diversity of cells constituting the central nervous system did not deceive last century neurohistologists in recognizing that this organ contained essentially two cell types: the nerve cells, or as termed according to the emerging concept of neural contiguity, the neurons, and the neuroglial cells. Neurons were clearly shown to be the means of excitability, impulse generation, impulse transmission, and connectivity in the neural tissue. The neuroglia, as indicated by its name (YAloc=cement or glue) given by Virchow (1860), was thought to be the cement- ing material...