The Edward H. Angle Memorial Lecture, presented at the twenty-first biennial meeting of the Angle Society, Maui, Hawaii, October 1975.

Presented before the Northern California Component of the Angle Society, March 1975.

Supported by U.S. Public Health Service Grants RR-05333, DE-03533 and DE-02668. From the School of Dentistry, Univ. of North Carolina.

Presented at the January, 1974 meeting of the Midwestern Component of the Angle Society.

From the Department of Orthodontics, Tokyo Medical and Dental University, Tokyo, Japan.

From the Dental and Nuclear Medicine Services, Veterans Administration Hospital, West Roxbury, Mass.

Read at the twenty-first biennial meeting of the Angle Society, Maui, Hawaii, October, 1975.