From the Departments of Obstetrics and Gynecology and Anatomy, Harvard University, Boston Lying-In Hospital, Boston, Mass.

The author is greatly indebted to Col. F. M. Townsend, MC, USAF, Director of the Armed Forces Institute of Pathology, Washington, D. C., for his generous help throughout this work. The interest and advice of Dr. Hans F. Smetana have been of great aid.

Submitted for publication Mar. 10, 1961.