Many of you probably already know this, but I thought it would be interesting to those who don't: "As the match went on, an incident occurred that led to the introduction of a rule that is still in force today. The Barnsley right half Glendenning was off the field receiving treatment for an injured foot. West Bromwich attacked the Barnsley goal and with the Barnsley goalkeeper Cooper beaten, Glendenning ran on to the pitch with one boot on and cleared the ball away from the Barnsley goalmouth. After this incident, a F.A. rule was introduced that stipulated that a player who is off the field must receive the referee's permission before returning."