The bronco bucked across the savanna and collided with a barbed wire fence. Mr. Brock was thrown to the ground, the 700-pound stallion landing on top of him.

“I was very badly injured, but the nearest doctor was 26 days away on foot, through a narrow trail in the rain forest where you couldn’t take horses,” Mr. Brock told the British newspaper The Independent in 2014.

“Ed said, ‘Gosh, I was on the moon and I was only three days from a doctor,’ ” Mr. Brock recalled. “Sure, I said, but for those people who lived in the Upper Amazon, and the 50 million people we’re now dealing with in the U.S., they might as well be on the moon for the opportunity they have to get the health care they need.”

Stan Brock died on Aug. 29 at RAM’s offices in Rockford, Tenn., where he had lived ascetically since he founded the nonprofit outfit in 1985. He was 82. Robert Lambert, a RAM spokesman, said the cause was complications of a stroke.

RAM began operating initially in British Guiana and then expanded to the United States in 1992, starting out with a single pickup truck that hauled a single dentist’s chair. It opened its first American clinic in Sneedville, Tenn., in 1992 and still runs an airborne ambulance operation in what is now the independent nation of Guyana.