Tracy Goen, M.D., bush-country veterinarian, Texan, cowboy, and missionary, wearing sunglasses and royal robes fit for Liberace, gulps a travel mug of Nescafé as his pickup trundles along a sandbar road through central Nigeria's bush. Goen's eight-year-old son, Sam, bounces in the truck bed with a generator, two bicycles, three flats of soda, duffel bags, and several hitchhikers.

In Nigeria's Kogi state, Goen practices A-to-Z surgery, handling up to 296 procedures a year—everything from craniotomies to C-sections. Prayer and caffeine fuel his nonstop pace. With his pediatrician wife, Patty, Goen has five children ranging from Elise, 17, to Katie, 4. Their cinderblock home is walking distance from the 60-bed Egbe Hospital. Patients may travel for days to arrive at Egbe for treatment.

But on this Friday morning, it's Fulani King Magaraji's turn to treat this latter-day Livingstone. Goen drives to Okoloke village, where Fulani tribal chiefs will confer a title on this white man sporting ostrich-leather cowboy boots. Goen will become Garukua Fulani Yagba West—king for life and adviser to Magaraji, the highest-ranking Fulani king of Yagbaland, the name of the local region.

Goen is running more than an hour late for his own coronation. The 44-year-old checks his watch and says: "Hey, man, we're early. This is supposed to start at 10, and now it's only 10 after 11." He gulps more coffee.

On arrival, Goen, with his white-flecked beard, hangs out the truck's window greeting people. Everybody knows pullo bodajo, the white Fulani.

In Nigeria, oral storytelling remains a principal means of communication. Local chronicles may spread like wildfire across hundreds of miles of bush country. Six years ago, stories of supernatural ...