Received for publication July 18, 1951. * Present address: Evans Memorial Hospital, 65 E. Newton St., Boston, Mass. t Present address: Dept. of Internal Medicine, Cincinnati General Hosp., Cincinnati 29, Ohio. The authors wish to express their thanks to the many persons whose interest and help made this work possible: Col. W. M. Blunt, Commanding Officer, Camp Carson; Col. T. E. Harwood, Jr., Post Surgeon; Lt. Col. James M. Blanton, Chief of the Medical Service; Capt. Howard C. Coggeshall, Officer in Charge of Acute Respiratory Diseases; Col. H. H. Twitchell, Chief Surgeon of Second Air Force, Peterson Field, Colo.; Maj. I. M. Dixson, Chief of Medical Service, Peterson Field; and the many other officers and men at Camp Carson who assisted in these studies. The authors gratefully acknowledge the technical assistance in the laboratory of V. G. Hamburger, S. Juster, M. E. Koshlund, M. Moorvitch and M. Smith. We are grateful to Mr. William Kruskal, Instructor, Statistics, for his statistical evaluation of the data.