Thom Gilligan read the e-mail and shook his head in disbelief. Here was yet another applicant for the 2005 Last Marathon, the extraordinary race in Antarctica that Gilligan had conceived a decade ago. No surprise there; while the event had been closed out for more than a year, adventure-minded runners were still begging for a chance. The shock was that this guy, 47-year-old William Tan of Singapore, proposed to do the 26.2 miles of loose rock, glacial streams, and ice in a wheelchair - a feat never attempted, never suggested in the previous six editions of the race. "I thought, no way," Gilligan says.