A PROPER RECONNAISSANCE of the zone begins with the old Gorgas Hospital on Ancon Hill, just west of Panama City and contiguous with the town of Balboa. At this hospital, a native Alabaman named William C. Gorgas brought yellow fever and malaria under control. As the first sanitary officer of the Isthmian Canal Commission of the United States of America, Gorgas contributed as much as any politician, engineer, or military officer. His medical breakthroughs made the difference between the muddy disaster abandoned by the French and a completed and functioning canal.      Gorgas had inherited the hospital that the French Canal Company had built in 1882 and staffed with nuns. Potted plants set in water on the grounds had provided breeding places for mosquitoes, before the insects were recognized as vectors for yellow fever and malaria; Gorgas' determined efforts would dramatically reduce the incidence of these and other tropical maladies. But canal officials were reluctant to concede to his requests, like those for screens for his hospital windows. Col. George Washington Goethals, who took over as chief of canal construction in 1907 and proved to be an autocrat, as his nickname Czar of the Zone implies, reportedly complained that every mosquito Gorgas eradicated cost the government $10.      The hospital was eventually screened and served as a crucial bulwark between the work force and the elements. In 1919 it was completely rebuilt on its steep, lush, 33-acre site. The main structure was made of concrete and had the neo-Classic tile roof that would become characteristic of official canal architecture. It was renamed for Gorgas long after he had departed Panama and is fenced and deserted now, brooding under palms, a symbol of professional resolve in the face of the natural-and official-antagonism that characterized the early, heroic years of canal building.      Next door is Quarry Heights, built on landfill and envisioned early on as a North American enclave. The Heights, which had become the residential area for ranking U.S. military brass has been deserted since it was handed over to Panama in January of this year. The Panamanian police, who now occupy the guard house at the entrance, allowed me to walk the neighborhood, where groundskeepers armed with leaf blowers attack remnants of a drought brought on by El Nino. Beyond tended landscaping, the houses themselves showed little sign of upkeep. Their overhanging corrugated iron roofs, covered with blue green patina, shaded ghostly, faded white clapboards.      The awning connecting the officers' club to the street had been removed.  Successive U.S. generals had lived at the end o the block, but when I looked through a window, I saw floors in need of polish; the big screened porch where drinks were once served seemed forlorn.  The lawn, brown in the heat, overlooked the distant canal, where a container ship waited to be flushed through to the Pacific. the r