Previous study of the histologic structure of nerve roots1 has provided criteria for the differentiation of sensory and motor roots. On the basis of these criteria it was possible to demonstrate that the glossopharyngeal nerve and the vagus-spinal accessory complex contain certain roots which conform in structure to motor roots and others to sensory roots. It was my purpose in this study to follow the nerve fibers of these roots to their respective nuclei in the medulla oblongata and thus to test these conclusions.
The material for this study consisted of the brain stems of a 7 month premature human fetus, a full term newborn infant and a human adult, all of which were stained for myelin sheaths by the Weigert-Pal technic. In addition, the brain stem of a human adult was sectioned and stained with thionine for nerve cells after fixation in alcohol, and another was impregnated