Read at the April, 1965 meeting of the North Atlantic Component of the Angle Society.

From the Department of Orthodontics, Odontological faculty, University of Gothenburg, Gothenburg, Sweden.

This study was supported financially in part by General Research Support Grant 1 SOI FR-05039-01 at Temple University, School of Dentistry.

From the Department of Orthodontics and the Dental Institute of Experimental Research, Dental Faculty, University of Oslo, Oslo, Norway.

From the Department of Orthodontics, Univ. of Örebro, Sweden.

Taken in part from a doctoral thesis, Department of Anatomy, Queen's University, Belfast, Northern Ireland. Supported by a research grant from the Northern Ireland Hospitals' authority. Presently at the Department of Orthodontics, University of Manitoba, Winnipeg, Manitoba, Canada.

From the Institute of Experimental Research, Dental Faculty, University of Oslo, Norway.

From the Department of Orthodontics, Univ. of Pittsburgh.