While in the course of his employment claimant was injured by having slipped and fallen on a slippery floor while engaged in a playful "tussel" with a fellow employee. The evidence sustains the board's finding that the affair (which includes its precipitating antecedents) which gave rise to the injury was incidental to and arose out of and in the course of his employment. Decision and award unanimously affirmed, with costs to the Workmen's Compensation Board.