what does "a bellow of pain"mean? he yelled? He jogged down the stairs, his mobile already out of his pocket, so exhilarated that he did not concentrate on where he was going, so that he took a corner on the stair and let out a bellow of pain as the prosthetic foot slipped on the edge; his knee twisted and he fell, hard and heavy, down six stairs, landing in a heap at the bottom with an excruciating, fiery pain in both the joint and the end of his stump, as though it was freshly severed, as though the scar tissue was still healing. “Fuck. Fuck!”