A man on a subway in Midtown East was slashed on the head after arguing with another rider, police said. The clash happened Dec. 20 around 4:40 p.m., when a 38-year-old straphanger aboard a crowded southbound No. 6 train nearing the Lexington Ave.-51st St. station and another man got into a heated d ispute after bumping into each other, cops said. The attacker whipped out a sharp object and slashed the man on the head before exiting the train and fleeing on foot. The victim was transported to Bellevue Hospital in stable condition. The suspect is described as having a dark complexion and was last seen wearing a dark sweatshirt and a green hat. Anyone with information regarding this incident is asked to call the NYPD’s Crime Stoppers Hotline at 1-800-577-TIPS (8477). All tips are confidential. ...read more read less