An adult male cadaver in which the left superficial palmar arterial arch is completed by a superficial palmar branch from the radial artery and giving rise to 1 proper and 4 common palmar branches. The first common palmar branch was a common trunk for the arteria princeps pollicis and arteria radialis indicis. The radial artery which passed on to the dorsal side did not give any branches to the thumb. The entire arterial supply to the left thumb was provided by the superficial palmar arch, which was the common trunk. The thumb is the distinguishing character of the human hand. The importance to the arterial supply of the thumb in the present case was that it is solely provided by the superficial palmar arch. A potential lethality could exist in the event of traumatic injury to the superficial palmar arch.