Manuel J. Davis, 72, a Washington attorney since 1933 and a former special counsel for the old D.C. Transit System, a predecessor of Metro, died Wednesday at Sibley Memorial Hospital following a heart attack.

Mr. Davis, who was a partner in the law firm of Herrick, Allen, Davis & Bailey at the time of his death, had a general law practice. But much of his work was in the field of probate and corporate law and representing clients before the Interstate Commerce Commission, the Securities and Exchange Commission, the Federal Trade Commission and at the Transportation and Interior departments.

Mr. Davis was general counsel and a stockholder of the old Washington, Virginia & Maryland Coach Co., Inc. When that system was acquired by the D.C. Transit Co. in 1964, Mr. Davis was retained as a special counsel. He held that position until D.C. Transit became part of Metro in 1973.

A native of Philadelphia, Mr. Davis grew up there an in Atlantic City, N.J. He was graduated from the Dickinson School of Law at Carlisle, Pa., in 1932 and then moved to Washington, where he earned a doctorate in law at George Washington University.

He went into private practice here in 1933 and continued in it until his death.

Mr. Davis was a member of the American Bar Association, the Bar Association of the District of Columbia and the D.C., Virginia Bar and Inter-American bar associations. He was a member of the bar of the U.S. Supreme Court and the bars of other courts.

He was a Mason and a past master of the Masonic Lodge National 12, the Mithras Lodge of Perfection and the Almas Temple. He also was a member of the University Club, the Capitol Hill Club and the Chatterbox Club, of which he was chief, or president, for many years. He was active in Republican Party affairs.

Mr. Davis's survivors include his wife, Sarah Frazier Davis, of Washington, four sisters, Lillian Emder, Dorothy Goldwyn, Mildred Fisher and Florence Rich, and three brothers, David J., Edward A. and H. Bernard, all of Washington.