The Hampé Experiment

    (A) In reptiles and mammals, the two paired bones of the distal hind limbs are the tibia and fibula, which articulate with the metatarsal bones of the foot through a series of small tarsal elements in the ankle. (B) In modern birds, the tibia is fused with the tarsal bones as the major limb element (the tibiotarsus or "drumstick"), and the fibula has withdrawn from the ankle articulation and develops only as a small proximal splint.

    Hampé (1960) inserted a thin slip of non-porous mica between the developing tibia and fibula of an embryonic chick (C). Separated from the inhibitory growth field of the tibia, the fibula grew to the same length as the tibia (D). The extended fibula also induced re-formation of the metatarsals as separate elements from the tibia (E), producing a condition resembling that of the bird ancestor Archaeopteryx.