[Experimental study of the effect of the ectoderm on the chondrogenic differentiation of the mesoderm of the mouse embryo limb in vitro. Results of a histological analysis].

The histological study of cultures of distal limb bud tips of 11 days old Mouse embryos and of dissociated mesoderm obtained from identical tips enabled us to demonstrate that distal bud mesoderm spontaneously differentiate into cartilage in vitro if its normal ectodermal covering is removed. If the ectoderm is present in situ or in close vicinity, the chondrogenic differentiation does not occur and mesodermal cells develop into a loose mesenchyme where numerous mitosis are observed. Experimental associations performed between limb bud mesoderm and epithelial sheets other than limb ectoderm demonstrated that the properties of this ectoderm are specific.