An analysis of feather germ formation in the embryo and <i>in vitro</i>, in normal development and in skin treated with hydrocortisone

Abstract

Abstract The initial phases of feather development in the saddle tract of embryonic chick skin were examined in situ and in vitro , under normal and various experimental conditions. A birefringent, fibrous lattice was found in the dermis; it has a strikingly grid‐like organization and is probably collagenous. The development of dermal papillae coincided with a characteristic distribution pattern of dermal cells in relation to this fibrous lattice: elongated cells were aligned along the tracts of the lattice; rounded cells formed clusters at the intersections of the lattice which represented the sites of the future dermal papillae. Evidence is presented that the cell clusters at the lattice intersections are the precursors of the dermal papillae and arise by aggregation of cells that migrate along the fibrous tracts. The results of this study point to a close involvement of the lattice in the formation of the individual condensations of prospective papilla cells and in the patterned distribution of dermal papillae in the dorsal feather field. Experiments with collagenase have shown that the integrity of this lattice is essential for feather morphogenesis. Skin treated with hydrocortisone at the appropriate stages of embryonic development lacks the organized fibrous grid and does not form feathers. The generation of these integumental structures is discussed in the context of epidermal‐dermal interactions.