The knotty limb pattern appearing fairly frequently on surgical instruments resembles the limb or trunk of a tree. It could be used as a criterion for identifying tools as surgical.
Some scholars claim that the motif is limited to instruments particularly liable to cause pain.
Yet it is more likely that, given the widespread worship of Hercules in the Roman world, the Hercules motif was adopted by the mainly Greek physicians in order to please their Roman clients. Although the episode portrayed here belongs to the mythical Trojan cycle, it is unknown to the extant literature. Ancient mythographers do tell us, however, that Achilles was trained in medicine by Chiron the centaur-sage. Although Achilles was invincible in battle, he is shown here as an inept medic. He is attempting to make a criss-cross tourniquet which will be at once comfortable and capable of staunching the wound.