Spinal nerve primary branches ( spb ; Galen (c192) ) : In general, each spinal nerve trunk divides distally into a spinal nerve dorsal branch (Meckel, 1817) and a spinal nerve ventral branch; this arrangement was identified in macrodissected adult animals except humans in the second century by Galen; see translations by Duckworth (1962, p. 229 ff.) and May (1968, pp. 597-599); for contemporary terminology see Durward (1951, p. 1052 and Fig. 913).