Axon terminal ( Barker, 1899 ) : A swelling-terminal (Cajal, 1899)-at the end of an axon trunk, axon collateral (Cajal, 1899), or terminal arborization (Cajal, 1888) that is presynaptic and usually rather simple although more elaborate configurations are found. First illustrated by Deiters (1865, Tab. 1, Fig. 1-b; Tab. 2, Fig. 6-b; see Van der Loos, 1967, p. 44), first interpreted correctly by Cajal (1888, Tab. I), and named thus by Barker (1899, p. 88, "terminals of one axone").