Editor's Note: The original manuscript has been freely edited to facilitate understanding of terms and phrases which are not in common usage in America. The hazards of inter-continental mail and the factor of time have prevented Dr. Muzj from checking the editorial changes. The assistance received from Dr. Allan G. Brodie in interpretation of the author's manuscript is gratefully acknowledged.

†Portion of an address delivered at the Edward H. Angle Society of Orthodontia on October 11, 1939.

*Presented at the meeting of the Midwest Component of the Edward H. Angle Society of Orthodontia in Chicago, November 1, 1938.