A disputed call on a fly ball down the LF foul line at the Polo Grounds touches off a melee in which New York Giants Billy Jurges and umpire George Magerkurth spit at each other. Both will be fined $150 and suspended for 10 days. National League President Ford Frick announces that two-foot screens are to be installed inside all foul poles to prevent future arguments. The American League will eventually also adopt the rule. The Giants lose, 8 – 4, to the Cincinnati Reds, and will add another eight in a row to take them out of contention.

On July 15, 1939 A disputed call on a fly ball down the LF foul line at the Polo Grounds touches off a melee in which New York Giants Billy Jurges and umpire George Magerkurth spit at each other. Both will be fined $150 and suspended for 10 days. National League President Ford Frick announces that two-foot screens are to be installed inside all foul poles to prevent future arguments. The American League will eventually also adopt the rule. The Giants lose, 8 – 4, to the Cincinnati Reds, and will add another eight in a row to take them out of contention.

Source
Baseball Reference July 15