IN AN ARTICLE written some time ago on mandibular repositioning in obstructive deafness and tinnitus, I1 advanced the theory that the genetic relationship of the musculature of the mandible, the auditory tube, and the middle ear may be a causative factor. In that article I stated that in the embryo the oral cavity is not distinctly separated from the pharynx, Eustachian tube, and middle ear. The nasopharynx and the nasal cavity become distinct when the palate is formed. The middle ear, Eustachian tube, pharynx, and mouth are lined with mucous membrane. This fact is directly related to the developmental relations of the parts, since the middle ear may be considered a partially separated portion of the pharynx and mouth. In the embryo is also found the pterygoid mass, which splits as the embryo develops. It finally becomes three distinct muscles. The main bulk of the pterygoid mass becomes the