Dr. Daniel A. Ruge, the White House physician who made crucial decisions in the care of President Ronald Reagan after he was shot in 1981, died Aug. 30 in Denver. He was 88.

Mr. Reagan went back to the White House 12 days after the shooting. Many doctors credited his recovery, if not his survival, to Dr. Ruge's decision not to disrupt the hospital's routine.

But Dr. Ruge later said in interviews with this reporter that he erred in neglecting to invoke the 25th Amendment to transfer presidential powers to Vice President George Bush temporarily, because of Mr. Reagan's need for emergency chest surgery, requiring general anesthesia, and for later treatment in an intensive care unit.

Dr. Ruge said he had studied the Constitution during the 10 weeks that Mr. Reagan had been in office and carried a copy of the 25th Amendment in his bag. Section 3 of the amendment should have been invoked to transfer executive powers to Mr. Bush for at least a day or two, Dr. Ruge said, "because Mr. Reagan could not communicate with the people a president is supposed to communicate with."

Dr. Ruge, whose thick crop of gray hair topped a 6-foot-2-inch frame, was an unassuming, self-confident man capable of self-criticism. Despite his knowledge of the Constitution, he said he did not think about applying the 25th Amendment because of the frantic nature of the moment. He also said he was not sure what would have been the right time to revoke the declaration transferring power.