NEW YORK -- Three blocks from ground zero, exhausted rescue workers hobble into a triage center, desperately in need of fluids, medicine and a bath. One patient is fast asleep after being given antibiotics and pain medication. He's worked several 16- and 17-hour days, and his body can't take it anymore. The patients, in this case, are dogs, trained to sniff out signs of life and death. Just like their human handlers, these German shepherds are suffering while sifting through the rubble of the World Trade Center. One dog fell 50 feet, another one 30 feet. Both survived, vets say. One dog had to be shot to death by its handler after being severely injured within the pile of rubble. This makeshift center, run by the Suffolk County SPCA and staffed by local veterinarians, opened within hours of the terrorist attacks on the World Trade Center. It has treated more than 300 animals from as far away as Mississippi, Georgia and Canada. "It's a lifesaver," said Robin Eckel, an officer with the Monmouth County Sheriff's Department in New Jersey. Eckel's dog, Chino, lost a toenail Saturday while searching supply vehicles entering the Holland Tunnel, which leads into lower Manhattan. If Eckel had had to treat the injury himself, he would have had to drive home, an hour away. "He's cleared to work again," Eckel said, leaving the tent hospital set up on West Street. "The vet said as long as he wants to work, let him work. It's not a serious injury." Every hour, five or six dogs come through the triage center. Nearly all require their eyes washed out and their paws massaged, as well as a liter of intravenous fluids. Some need antibiotics. Most are bathed. The center is equipped with a donated blood-testing laboratory that can check each dog's kidney and liver functions within minutes. Using that information, vets can determine each animal's ability to press on. "We have enough stuff here to run a couple hospitals if we really needed to," said Dr. Jason Heller, a veterinarian with Central Veterinary Associates in Long Island. "God forbid one of these dogs can't go back in and find someone--that's why we're here." Vets from around the country have called to offer help, said Dr. John Charos, who works with Heller. Some offered to drive 24 hours to bring dog food and other supplies. (The vets say they now have enough.) Pharmaceutical companies have donated medicine. A pet supply company donated a case of special booties for the animals. K-9 handlers stop by before and after their shifts, and during breaks. "They're more worried about the dogs than themselves," one veterinary technician said. Joaquin Guerrero, a K-9 officer from Saginaw, Mich., brought in his dog, Rookie, to get bandaged during a break from work. Guerrero didn't want steel or debris to cut the dog's legs or paws. "I'm going till I can't go no more, till the dog can't go no more," Guerrero said. "So far, he's running good. He's very alert." Ammo, the exhausted dog asleep on the grass under a blanket, doesn't even flinch when a photographer's flash goes off. Ammo has traveled the world and has helped rescue 2,000 people, said Michael Norkelun of the Suffolk County SPCA. "He's used to working," he said. "He just worked a little too hard this time." When Ammo detects a person alive, he starts digging. When he finds the dead, he lies down. Ammo has found no one alive in the ruins of the World Trade Center. For information about reprinting this article, go to http://www.lats.com/rights/register.htm Dogs Toil to Edge of Collapse Search: Veterinarians set up on-site clinic to treat K-9s for pain and exhaustion. Then it's back to work.