Mutilation is about inflicting injury, but the aspects of pain are less conceptually homogeneous.
Animal mutilation seems a good place to start, because it always creates lively debate and a wide range of theories. Although, most of this article will deal with the sexual expression of mutilation, the subject of animal mutilation in other contexts needs to be exposed first, although it is still unclear to what extent sexual pleasure is involved even when it may not be the primary motivator. The wide range of theories appropriated to animal mutilation phenomena, have been going on for more than three decades and yet definitive explanation still eludes us. Partly because much of the evidence seems so incredible. For example, in theory it is impossible to drain all of the blood from a still-living cow.