A thermal pack (10) and associated control system (32, 44) for the therapeutic treatment of a mammal. The pack (10) is made from a flexible, heat conductive, liquid impermeable material and has an inlet (18) through which fluid can be transferred into the pack (10), a passageway through which fluid can flow and an outlet (20) through which fluid may be removed from the pack (10). The passageway within the pack (10) also has a separator element (22) that forms a track (22, 24) along which the fluid can flow and keeps the walls of the pack (1) spaced apart so that the fluid flow is not restricted if the pack (10) is flexed in use.