The growth of arbors into the cuneate nucleus of a macaque monkey 11 yr after the amputation of a forelimb at shoulder level. (a) A series of coronal sections through the lower brainstem showing the label on the deafferented side (Left) and the normal side (Right) from bilaterally matched injections in the chin. Note that there is no label in the pars rotunda of the cuneate nucleus on the normal right side, but a small region of the pars triangularis of the cuneate nucleus adjacent to the trigeminal nucleus is labeled. The fine circular line in the cuneate nucleus defines the pars rotunda, and the fine line in the trigeminal nucleus defines the substantia gelatinosa. (b) A dark-field photomicrograph of a section intermediate to sections number 143 and 149 shown in a. The lines in the ventral part of the pars rotunda mark the territories of the digit representations seen in cytochrome oxidase preparations (43). Cu.Ro., pars rotunda of the cuneate nucleus; Cu.Tri., pars triangularis of the cuneate nucleus; Trigem, trigeminal nucleus; D, dorsal; L, lateral.