Sawhorses barred the entrance to the Giraffe House at the Baltimore Zoo last week. Four-year-old Julia Dunning wanted to know where the giraffes had gone and if there was a giraffe hospital on the grounds.

"You used to see three or four of them in the yard at once," said her mother, Roberta. "They were golden brown. They always seemed so at peace, looking down at the world."

It has been a long, hot summer for the keepers of the long-legged, long-necked and normally long-lived giraffes at the Baltimore Zoo.

A mysterious and deadly "wasting syndrome" has decimated the zoo's giraffe population. It killed the giraffe known as Rocky last year and unstrung Pearl the year before that. Last month, in succession, Scarface, Termite and Prudence died.

Then, in September, it was Colleen, the beloved 5-year-old Baltimore-born creature who was showered with cards and toasted by several thousand well-wishers at a zoo-sponsored birthday party last March.

The worst blow came last week when Patience, an otherwise fit and healthy giraffe, died of stress after the complicated birth of a stillborn calf. That ill-starred turn apparently is unrelated to the wasting syndrome, but nonetheless is no easier to accept for the bereaved keepers, school-children and thousands of adults instilled with a sense of wonder by the sight of the world's tallest creatures towering over a fence or ambling languidly through the grass.

For zoo officials, Patience's fatal pregnancy was doubly devastating after the losses of the past two months. Instead of Patience nursing her newborn calf--at birth already taller than most men--the keepers had to haul the pair to the heavily worked burial site on the zoo grounds.

Mayor William Donald Schaefer stopped by to pay his respects and offer a few encouraging words. Letters of condolence poured in from people around the country, and callers expressed their sympathy from as far away as South Africa.

"A lot of hopes were riding on Patience," said zoo director Brian Rutledge. "The closest thing I can compare it with is that it's like losing a friend to cancer."

And now the Giraffe House, once a merry tenement filled with nine reticulated specimens of the desert-dwelling Angola race, is as somber as a morgue, closed to the public while zookeepers mop up after the autopsies and anxiously monitor the health of Raymond and Angel, the only long-necked tenants left.

Meanwhile, scientists from five institutions, including Johns Hopkins, the National Zoo, the University of Maryland, the National Institutes of Health and the University of Guelph in Ontario, search for clues to the disease.

The animals apparently all died of ganglioneuritis, a disease that attacks the nerve endings in the intestines and causes a loss of appetite, anemia and malnutrition. How the giraffes contracted the disease still is not clear.

"We don't know the causal factor," said Rutledge, whose zoo keepers worked around the clock for five days on Colleen, warming her with electric blankets and rolling her from side to side every two hours to keep her own weight from cutting off the flow of blood to her legs. "We've methodically gone through temperature, day length, season, whether the creatures were inside or outside. I suspect it might be a trypanosome protozoan transmitted by fly bite, but we don't really have a problem with flies."

Giraffes have been kept in captivity successfully since at least 1500 B.C., when they were prized by the Egyptians. In the early 19th century, the creatures were brought by sailing vessels to menageries in Europe.

Apart from their conspicuous height, they have many remarkable attributes. Their long necks evolved chiefly to enable them to nip the leaves of the acacia tree, while their legs can administer powerful punishment to unwary lions, their only natural enemy.

"They could kick your head off, and I don't mean figuratively," Rutledge says.

Giraffes rarely sleep longer than 20 minutes in a night and, much as in the human world, giraffes of inferior rank lower their heads when a high-ranking member of the herd passes. They reach ages of 30 years or more, heights of 19 feet and weights of more than a ton.

In her book, "Out of Africa," Isak Dinesen described the splendid spectacle of wild giraffes on the move, with "their queer, inimitable, vegetative gracefulness, as if it were not a herd of animals but a family of rare long-stemmed, speckled gigantic flowers slowly advancing . . . . "

While the birth of a giraffe at a zoo is an event, it is not uncommon. Nor is it unusual for groups of giraffes to perish of "wasting syndrome" at zoos, according to Rutledge, although no other zoo has lost as many giraffes as quickly.

The giraffes at the Baltimore Zoo belong to the reticulated species, one of the two species in the giraffe family, and all were Angolan giraffes, one of eight races. Until the rash of deaths, the Baltimore Zoo had hoped to develop a breeding herd of Angolan giraffes.

All of the deaths occurred in late summer or early fall. The weather was hot, but no hotter than the sunbaked African habitat to which the free-ranging giraffes are accustomed. The giraffes developed patches and sores on their coats and began to slobber. As they lost control of their facial muscles, they began to "mumble" their food, spilling their vitamin-supplemented grain.

In the case of Termite and Colleen, death apparently was hastened by listeria, a bacterial infection that causes lesions in the brain. Toward the end, Termite's left ear and eyelid drooped and he began to circle to the right.

Zoo officials have kept meticulous records on feeding habits of the residents of the Giraffe House. Autopsy teams from Johns Hopkins have taken blood samples and collected tissue from the stricken creatures, and found "a black mass of deteriorated tissue" in place of the nerve endings in the gut. Researchers at the University of Guelph in Ontario are trying to cultivate the organism that causes the ganglioneuritis, and diagram how the disease is being transmitted.

Thus far, there has been no effective way for the zoo to treat the ailing giraffes.

"We can't give them penicillin," Rutledge said. "They need the flora in their digestive system. They have three stomachs. We'd be killing them with kindness."

Until the method of the disease is uncovered, zoo officials do not plan to replace the giraffes or reopen the Giraffe House. Raymond has been permitted outside the 20-foot doors of the Giraffe House to stretch his neck and his six-foot-long legs, which is what he was doing one day last week, twirling his tail, reaching for a mouthful of beech leaves with his black tongue and casting an occasional big wet eye in the direction of the two-legged creatures admiring him from the railing.

They were members of an upcoming Kenya safari sponsored by the ornithology department at Cornell University, and they had been instructed to practice photographing animals in a zoo before turning their viewfinders on animals in the wild. Shutters clicked as Raymond assumed the pose of an African giraffe chewing a beech twig.

"Well, goodbye Raymond," one woman called as the group moved away. "I hope you survive."