Labelled fibers ran dorsally in a position medial to the spinal trigeminal nucleus and innervated the ventrolateral, medial and commissural subdivisions of the nucleus of the solitary tract as well as the dorsal motor vagal nucleus (see Figs. 30-R, 7C,D). In sections through the rostral nucleus of the solitary tract there were numerous medium and fine wavy fibers with many varicosities along their lengths. Labeled fibers were not seen in the rostral nucleus of the solitary tract in experiment R678 in which the injection site was confined to the ILC, indicating that this projection may originate from the prelimbic cortex (see below). In experiment R651, the pattern of fibers seen in the medial subdivision of the nucleus of the solitary tract was similar to the rostral subdivision, with the addition that finel abelled fibers with boutons and swellings swept into the layer of ependymal cells lining the fourth ventricle (Fig. 7D). The ventrolateral portion of the nucleus of the solitary tract was innervated by fibers that appeared to be a continuation of the thick, straight axons of the lateral tegmental pathway. These axons branched profusely giving rise to numerous medium and fine caliber fibers bearing boutons and varicosities along their lengths. The commissural portion of the nucleus of the solitary tract was innervated by a few fine-labelled fibers that had stalk-like processes and boutons along their lengths.