Fig. 3.

(A–D) Photomicrographs showing axons that were anterogradely labeled following an injection of biotin dextran into the medial gray matter of the S2 segment of the spinal cord 18 days prior to sacrifice in two of the animals. The axons in the smaller box in (A), and shown at higher magnification in (B) are from an animal with a unilateral injection. The ascending axons were in the medial fasciculus gracilis on one side at C1. The labeled axons in (C) were in the medial fasciculus gracilis bilaterally at the L1 level in a different animal. The labeled axons and terminal boutons shown in (D) were in the medial part of the nucleus gracilis (Gr) and the solitary nucleus (Sol) in the same animal as that illustrated in (A,B). The calibration bar indicates a length of 190 μm for (A), 65 μm for (B) 112 μm for (C), and 73 μm for (D).