James Herriot, 78, who shared his experiences as a British country veterinarian in the best-selling memoir "All Creatures Great and Small," died of prostate cancer Feb. 23 at his home near Thirsk, in the Yorkshire Dales, where he had ministered to animals for half a century.

James Herriot was the pen name and alter ego of veterinarian James Alfred "Alf" Wight, who wrote 15 books in the time that he could wrest from his practice. About 50 million copies were sold in 20 countries. But Mr. Herriot continued his veterinary practice long after his books made him famous.

"If a farmer calls me with a sick animal, he couldn't care less if I were George Bernard Shaw," he once said.

A quiet, modest man with a trace of his Glasgow upbringing in his voice, Mr. Herriot kept out of the limelight as best he could. Despite the pen name and Thirsk's disguise as Darrowby, many fans tracked him down at Skeldale House, the ivy- covered home and office familiar to his readers and the viewers of the popular television series based on "All Creatures Great and Small."

Mr. Herriot, who was born in Sunderland in the north of England and raised in Glasgow, was the son of an orchestra leader who played background music for silent films. He trained at Glasgow Veterinary College and had planned to specialize in small pets, but fate intervened.

"The only job that came up was in Thirsk. It was not small pets in a clean surgery but big animals in a succession of muddy barns," he once said. After arriving in Thirsk in 1940 for a now-famous job interview with Donald Sinclair -- Siegfried Farnon in the book -- he joined the practice. Aided and abetted by the hapless Tristan (Sinclair's brother, Brian), he settled in among the dour farmers of the Yorkshire Dales.

He started writing when he was 50 years old. An avid soccer fan, he chose his pseudonym while watching a soccer match on television -- the goalkeeper for Birmingham City was named James Herriot.

His first two books in Britain were "If Only They Could Talk" and "It Shouldn't Happen to a Vet." Both sold modestly, but they became an instant best-seller in the United States when they were combined and released as "All Creatures Great and Small," a phrase borrowed from an English hymn for children. "The Americans saved me without a doubt," Herriot recalled in an interview several years ago.

Mr. Herriot wrote his veterinary stories in a conversational, first-person style. He worked out most of them while driving along the rural lanes between farms. "I spend a lot of time alone, and it gives me something to think about," he said.

"I was dumbfounded by the reaction to that first book, absolutely dumbfounded," he told the Daily Mail in 1981. "The most I had hoped for was that someone would publish it and a few people quite enjoy reading it."

He continued writing up to a few weeks ago, publishing his "Cats" series of children's stories just before Christmas.

Actor Robert Hardy, who played Siegfried in the television series, described Mr. Herriot as "a modest man, a private and honorable man. He was also a fine vet. When fame came to him, he found it quite a problem, but he struggled through all that."

Mr. Herriot was made an officer of the Order of the British Empire in 1979.

Survivors include his wife of 53 years, Joan Wight; a son, James, who runs the veterinary practice; a daughter, Rose Page; and four grandchildren. CAPTION: JAMES HERRIOT