CHICAGO — When the Chicago Cubs pitcher Travis Wood unexpectedly hit a home run Saturday night in Game 2 of his team’s National League division series against San Francisco, the baseball found a happy nesting spot in the left-field bleachers at Wrigley Field. The Cubs fan who snared it even returned it to Wood after the game rather than keep it as a memento.

But at Wrigley, not all home runs are received equally.

A longstanding protocol there dictates that when a visiting player hits one out, any upstanding Cubs fan who catches the ball is obliged to launch it back onto the field.

Even the people who position themselves beyond the outfield walls at Wrigley and attempt to snag home runs hit onto Sheffield and Waveland Avenues sometimes follow this code.

It is a symbolic act, turning the baseball into a bitter pill that is better spit out than swallowed.