To describe the ganglion-cells of the Mammalian spinal cord as confined to the grey substance of the cord is not quite strictly correct. Beisso was the first to draw attention to the fact, that apart from axis-cylinder processes which pass into the ventral roots from cells of the ventral cornu, there project also from those cells of the cornu which lie next the white column other branches to mingle with the fibres of the bundles of the ventral nerve-roots. The ganglion-cells of the grey matter often, by one or more of their processes, jut partially into the white matter. The descriptions of Beisso, Pick, and Schiefferdecker have further shown that in certain situations in the anterior and lateral columns, ganglion-cells lie outside the grey substance in the surrounding white matter. Since Gaskell, in 1885, drew attention to the ganglion-cells in the cord of Alligator, lying at the periphery of the antero-lateral column, and, of course, quite removed from the central grey matter, I have often searched in the cord of the Mammalia for evidence of similarly situated cells; always, however, without success. The search has, however, persuaded me that isolated ganglion-cells are no infrequent constituents of the white columns. The cords examined by me have been chiefly those of Man, the Monkey (Bonnet, Jew, and Rhesus), and the Dog. A number of sections have also been prepared from the Cat, Lion, Calf, Bat, Mouse, Rabbit, and Guinea-pig. The out-lying ganglion-cells in the white matter may conveniently be considered in three sections, according as their situation is within the anterior (ventral), the lateral, or the posterior (dorsal) white column respectively.