The circumstance that the oculomotor or third cranial nerve supplies no fewer than seven, muscles of the eye, two of them intrinsic and five extrinsic, and the fact that these muscles may be paralysed either singly or in groups as the result of central lesions, naturally suggest that each muscle is represented in the nucleus by a separate group of nerve cells. Hitherto, however, the anatomical text-books have been content with figuring the nucleus as a small indefinite group of cells lying in the anterior portion of the grey matter surrounding the aqueduct of Sylvius.