Read before the Society of Craniofacial Biology, Los Angeles, May, 1962.

This paper is based on a thesis submitted in partial fulfillment of the requirements for a Master of Science degree, Department of Dentistry and Dental Research, University of Rochester, 1961 and was supported by Research Grant D-1071 from the National Institute of Dental Research.

Condensation of the original thesis submitted as partial fulfillment of requirements for the Master of Science degree, Northwestern University, 1960.

* Supported in part by the State University of Iowa and in part by a research grant, D-217, from the National Institute for Dental Research, National Institutes of Health, United States Public Health Service.

College of Dentistry, Howard University. This study was financed in part by U.S. Public Health Service Grant Number 331 - 331 C5.