Presented at the meeting of the Pacific Coast components of the Edward H. Angle Society, November 10, 1950. Pebble Beach, California.

Presented before a joint meeting of the Pacific Northwest, Northern California and Southern California Components of the Edward H. Angle Society of Orthodontists, Pebble Beach, California, November 9, 1950, and at the Charles H. Tweed Foundation for Orthodontic Research, Tucson, Arizona, April 2, 1951.

Read before the Pacific Coast Components of the Edward H. Angle Society of Orthodontia, Pebble Beach, Calif., November 9, 1950, and before the Charles H. Tweed Foundation for Orthodontic Besearch, Tucson, Ariz., April 3, 1951.

*A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Dentistry, University of Washington, 1950.

Read before the Edward H. Angle Society of Orthodontia, French Lick, Indiana, November 1, 1949.

Paper presented April 4, 1951, before the Charles H. Tweed Foundation for Orthodontic Research, Tucson, Arizona.

* One important and obvious difference between steel and rubber is the amount of elastic deformation possible in the two materials. Under the same conditions, the extension of steel will be only about 1/100,000 that of rubber.