Abstract
The acoustic tumor of the human being has been studied with the electron microscope. The principal cell is identified with the lemmocyte previously described in silver carbonate preparations. Some unusual cytoplasmic inclusions have been observed. The neuritides have been shown to be long and slender cytoplasmic processes extending from the poles of the spindle-shaped principal cells. In addition to the common spindle form, the principal cell has been shown to present a variety of configurations. Its relation to the Schwann cell is briefly discussed.