* Portions of the material used in this paper were taken from a thesis submitted in partial fulfillment of the requirements for the Degree of Master of Science in Orthodontics in the Horace H. Rackham School of Graduate Studies, University of Michigan, Ann Arbor, Mich. June, 1942.

Read at the University of Michigan Orthodontic Alumni Meeting, Ann Arbor, Mich. Nov. 3 and 4, 1950. Preliminary work on this paper was read at the Research Section of the American Association of Orthodontists in Chicago, April 25, 1944.