The Germans call it wanderlust. Don Quixote called it knight-errancy. Kipling called it roguing and ranging. A whole genre of literature sprang from the call of the road and the lure of adventure. Think “Robinson Crusoe” or “Treasure Island” or even “Lord Jim.”Now, imagine a man who travels day after day, relentlessly, not because he wants to or because he is paid to, but because he absolutely has to: because roads are his master, and he their slave. This is what psychiatrists call “dromomania,” ambulatory somnambulism — the traveling fugue. The patient who brought that condition to full clinical light, the most notorious dromomaniac in history, was Jean-Albert Dadas, a gas-fitter who deserted the French army in 1881 and criss-crossed Europe in a trance for five years, making his way on foot to Berlin, Prague, Moscow, even Constantinople. He had no memory of it.