“…This observation together with the lack of molecular markers for young fast and slow motoneurons has led many investigators to favor initial nonselective innervation (for review, see Jolesz and Sreter, 1981). In contrast, the fact that neonatal rodent motor units are strongly biased toward one fiber type (for mouse, see Jansen, 1988, 1990; for rat, see Thompson et al, 1984Thompson et al, , 1987Thompson et al, , 1990; and for rabbit, see Gordon and Van Essen, 1985;Soha et al, 1987;Cramer and Van Essen, 1995) favors selective innervation, as do several other experimental studies in both chick and mammal (Feng et al, 1965;Hnik et al, 1967;Hoh, 1975;Soileau et al, 1987;Vogel, 1987;Vogel and Landmesser, 1987;Rafuse et al, 1996).…”