Dr. Clinton W. Gray, 67, veterinarian emeritus of the National Zoo where he worked for 15 years before retiring in 1978, died of respiratory failure Sept. 18 in Anne Arundel General Hospital in Annapolis. He lived in Riva, Md.

Dr. Gray joined the zoo in 1963 as head of its office of animal health and pathology. In 1975, he became the zoo's senior veterinarian, a post he held until retiring three years later as veterinarian emeritus.

When he joined the National Zoological Park of Smithsonian Institution, it was one of the less than 10, of several hundred, American zoos with a full-time veterinarian. The job was not easy.

While the average veterinarian is called upon to heal the odd kitten and puppy, Dr. Gray was confronted by more exotic and demanding patients, approximately 3,000 animals representing about 850 species. His accomplishments included the treatment of a broken leg belonging to a 350-pound giant tortoise, and successfully administering tuberculin tests to cape water buffalos with the use of dart guns.

In the mid-1970s, the authorities at Lion Country Safari in Doswell, Va., determined that their lions were overbreeding. Dr. Gray helped solve the problem by developing and administering contraceptive devices via his dart gun.

He told a Post reporter in 1967 that his patients were amazingly similar to humans in the ailments they acquired and their reactions to them. Dr. Gray did note one disimilarity: "They have a remarkable lack of colds," he observed.

Dr. Gray was a charter member of the American Association of Zoo Veterinarians, and a consultant to zoos around the world. He was the author or coauthor of numerous technical studies, including "Rheumatoid Arthritis in the Lowland Gorilla" and "Differential Band Staining on the Chromosomes of the Anthill Tiger."

He was a native of Delaware and earned his doctorate in veterinary medicine at Michigan State University in 1943. During the 1940s and early 1950s, he had a private practice near Gaithersburg, worked for the state of Maryland and the Agriculture Department, and was on the staff of a Nebraska laboratory. From 1955 to 1963, he was with the Agency for International Development, where he planned and directed programs for disease control in humans and animals in South America and Africa.

His marriage to Jean T. Gray ended in divorce.

Survivors include his wife, the former Mary Clare Cahill of Riva; a daughter by his first marriage, Betty Jean Aldrich of Davis, Calif.; his mother, Edna Gray of Lewes, Del.; a sister, Betty Rinshaw of Swarthmore, Pa., and one grandchild.