Peripheral nervous system ( PNS ; Meckel, 1817 ) : In bilateral animals, a topographic division with condensations of the nervous system (Monro, 1783) consisting of nerves (Herophilus, c335-280 BC) and ganglia (Galen, c173). When a PNS is present, its obligate companion topographic division is a central nervous system (Meckel, 1817). There is no known isolated part of the PNS that does not have a connection to the rest of the nervous system; see Bullock & Horridge (1965, pp. 9-14). While the nerves were discovered by Herophilus (335-280 BC; see Solmsen, 1961, p. 185; von Staden, 1989, pp. 250-252), the term peripheral nervous system as currently understood was first used by Meckel (1817; see English translation 1832, p. 153).