Dr. Nelson Mercer, 85, a retired lung specialist and medical officer for the Civil Service Commission, died Saturday after a heart attack at Doctors Hospital.

A physician who treated victims of gas attacks during World War I, when he was stationed with the U.S. Army in France, Dr. Mercer was a direct descendant of Revolutionary War Gen. Thomas Nelson, a signer of the Declaration of Independence and an early governor of Viginia.

He was also a great-great-grandson of Gen. Hugh Mercer, who was killed in the Battle of Princeton in 1777.

Born in Richmond, Dr. Mercer graduated from the Medical College of Virginia Cavalry.

Later, he joined the 29th Division in France, where he treated victims of gas warfare.

From 1925 to 1938, Dr. Mercer was engaged in private medical practive in Richmond. He then moved to Washington and worked for several government agencies, eventually joining the Civil Service Commission in 1942 as a medical officer in the medical retirement section. He retire in 1963.

He was a number of the American Medical Association, the Medical Society of Virginia and the Retired Officers Association.

Survivors include a daughter, Constance, of the home in Washington, and two cousins, Stuart and Annie Belle McGary, both of Richmond.