Who does Jack feel Ralph is always protecting?

In chapter 6: Beast from Air when the boys are discuss setting out to hunt for the beast Ralph appoints Piggy to remain behind and look after the littluns. jack says, and I quote... "That's right. Keep Piggy out of danger." Later, in chapter 7: Shadows and Tall Trees Ralph decides that someone should go and tell Piggy that the biguns will be delayed. Jack says sarcastically, and I quote... "We mustn't let anything happen to Piggy, must we?"