Distribution of osteo- and chondrogenic neural crest-derived cells and of osteogenically inductive epithelia in mandibular arches of embryonic chicks.

Mandibular arches of H.H. stage-22 embryonic chicks were divided into halves (lateral/medial; cephalad/caudal; or proximal/distal) and grafted to the chorioallantoic membranes of host embryos. All six halves formed both cartilage and membrane bone. Epithelial-mesenchymal recombinations performed between half mandibles showed (a), that the cephalad half of the mandible contained more chondrogenic cells than did the caudal half, (b), that the proximocaudal quarter of the mandible contained more osteogenic cells than the remainder of the mandible, and, (c), that the epithelium of the caudal half was more osteogenically inductive than was the cephalad epithelium. Differential distribution of mesenchymal cells and differentially inductively active epithelia are both components of this epithelial-mesenchymal interaction.