Collateral ( Waldeyer, 1891 ) : Short form of axon collateral (Cajal, 1899); name provided by Waldeyer (1891; see Shepherd, 1991, p. 36).

Neuron ( Waldeyer, 1891 ) : For the nervous system (Monro, 1783), the basic structural and functional unit at the level of cells (Hooke, 1665). The connections of neurons form the connectome and wiring diagram. Probably discovered microscopically by Dutrochet (1824; Pl. 2, fig. 20) in unfixed molluscan ganglia (Galen, c173) and named thus by Waldeyer (1891, p. 1352); also see Peters et al. (1991, p. 11).

Neuropil ( nep ; Waldeyer, 1891 ) : The gray matter (Meckel, 1817) compartment exclusive of cell bodies (Deiters, 1865) and vascular cells, thus consisting of the cytoplasmic extensions of neurons (Waldeyer, 1891) and glia (Virchow, 1846), including synapses (Foster & Sherrington, 1897). It was discovered histologically in spiders by Leydig (1855, p. 413), who called it the Punktsubstanz, or dotted substance in English; Waldeyer first used the term (1891, p. 1354). Also see Bullock & Horridge (1965, pp. 16, 27, 54), Peters et al. (1991, Ch. 11).