Growth and morphogenesis of the fibula in the chick embryo.

The development of the avian fibula was studied both histologically and experimentally. It was found that from the onset of chondrogenesis, the fibula possessed a smaller diameter than the neighbouring tibia. The truncated growth of the fibula was a result of the loss of its distal epiphysis between stages 27-31. This epiphysis subsequently became fused to the tibia and formed the fibulare of the tibiotarsus. The experiment of Hampé (1960) was repeated by inserting tantalum barriers into the limb between stages 18 and 23: this sometimes prevented the separation of the fibula distal epiphysis, thus giving rise to an elongated element. A similar result was obtained from grafts of polarizing region into the leg bud at stages 18-20. It was concluded that there was no evidence for competitive interaction between the blastemata of the tibia and fibula. In addition, the differential growth in diameters between the tibia and fibula was largely a result of differential osteogenesis rather than chondrogenesis as previously thought.