Summary of the histological findings from experiments during which the effects on the responses of VMl neurons of a microinjection of xylocaine into the caudal medulla were studied. A, Extents of the injection sites that depressed the responses of VMl neurons (n = 5). B, Extents of the injection sites that did not modify the responses of VMl neurons (n = 3). Cu, Cuneate nucleus;Gr, gracile nucleus; LRt, lateral reticular nucleus; mlf, medial longitudinal fasciculus;pyx, pyramidal decussation; RAmb, retroambiguus nucleus; Sol, nucleus of the solitary tract; Sp5C, trigeminal nucleus caudalis;SRD, subnucleus reticularis dorsalis;SRV, subnucleus reticularis ventralis;XII, hypoglossal nucleus.