The fissula ante fenestram is an irregular projection of the periotic connective tissue extending from the angle of junction of the vestibule and the scala vestibuli, through the otic bony capsule to the periosteum of the middle ear just below the pulley of the tensor tympani muscle. Little significance has been attached to this structure. The common view held by former authors is that it is a synchondrosis or possibly a place for expansion of the otic capsule. However, further studies have shown that this structure is constant in human otic capsules even into old age; that the capsule in this region is the usual locus or otosclerotic foci; that the tissue of the fissula resembles and is continuous with the loose periotic tissue of the vestibule at its junction with the scala vestibuli, and that the fissula becomes apparent and its character definite in the same manner and at