Axon ( Kölliker, 1896 ) : A neuron extension that in a chain normally conducts information away from the dendrites (His, 1889) and/or cell body (Deiters, 1865) to axon terminals (Barker, 1899), the presynaptic compartment (De Camilli et al., 2001) of synapses (Foster & Sherrington, 1897). Most neurons (Waldeyer, 1891) have one axon trunk with a variable number of axon collaterals (Cajal, 1899), and the presynaptic compartment may be (a) an axon varicosity (although not all varicosities form synapses) also called a synapse-of-passage, (b) a terminal-of-passage along the axon trunk or axon collaterals, or (c) an axon terminal (synonym: terminal bouton) at the end of an axon collateral or the axon trunk; see Swanson, 2004, Fig. 5). The axon was probably discovered microscopically in unfixed molluscan material by Dutrochet (1824, Pl. 2, fig. 2; see Van der Loos, 1967, pp. 22-23) and for vertebrates by Remak (1837; his primitive band). Axons were first distinguished clearly from dendrites by Wagner (1846, see Tab. 3, Fig. 43-a; see Van der Loos, 1967, p. 37), and named thus by Kölliker (1896, p. 2). It is common in vertebrates for the axon to arise from the cell body or a dendrite, as first demonstrated microscopically in macerated tissue from the Torpedo electric organ by Wagner (1846, Tab. 3, Fig. 43-c; see Van der Loos, 1967, pp. 38-39).