"All Creatures Great and Small," a 13-part BBC serial adapted from the first four novels of veterinarian James Herriot, has the potential to be unusually satisfying uneventful entertainment, temperature and sanguine to a degree that little television manages to be. Channel 26 has acquired the programs for telecast here, starting tonight at 8.

Herriot's reminiscences of life as the village vet in a Yorkshire country town of the 1930s have already been made into two motion pictures, but only one of them, "All Things Bright and Beautiful," was released theatrically in this country. The other, "All Creatures Great and Small," surfaced as an entry on the "Hallmark Hall of Frame" on NBC.

TV serialization may be the ideal format for treating Herriot's stories, episodic accounts that go from animal to animal and from one crusty but fair-minded villager to another. In tonight's first chapter, Herriot enters their lives as a confident and chipper young lad taken on as an assistant by the reigning vet for "four pounds a week and full board."

One obvious strength of this film-and-tape TV version is the transporting authenticity of the locale, a disarming little town that materializes like something out of "The Twilight Zone" or "Brigadoon." It looks like just the place any same citizen of the age of anxiety would love to retreat to. When the serial ends, of course, World War II will be loming like mad and so much for halcyon days of yore.

Brian Clark, who wrote this episode, and Terence Dudley, who directed it, refused to sentimentalize the relationships between people and animals. Indeed, there's a sudden close-up of a cow undergoing a particularly rectal form of therapy that has the potential to terrorize some viewers, though only for an instant. Also, children reared to the punch-line rhythms of Happy Dayses may find the program too dry and matter-of-fact.

But the details of country life and of fundamental values are pleasures to observe, whether the young vet is sharing ale with a grateful couple whose bull has been cured of sunstroke, or a jolly fat farmer, his cow now unclogged, who rejoices, "She's going on all four cylinders now!" It's clear that in this series we are going to meet fewer shrill, venal or callous people than we are decent people trying to behave honorably.

Christopher Timothy, in the role of Herriot, may have a limited range of responses, but they come across as genuine and civil. "All Creatures Great and Small" is quite bright and marginally beautiful.