STRUCTURE AND ACTIVITY OF EXPERIMENTALLY PRODUCED EPITHELIAL THICKENINGS IN CHICK EMBRYO LIMB BUDS

SUMMARY By applying slight pressure along a cranio-caudal plane on the dorsal surface of the wing bud, the proximo-distal sliding of the ectodermal cover was temporarily hindered and epithelial thickenings there developed, which persisted 30 to 50 hr. These heterotopical epithelial thickenings showed some morphological similarities to the apical ectodermal ridge. The histological observations and the mitotic recordings carried out on the mesenchyme underlying the thickenings in various phases of their development and regression, as well as the study of the development of the whole bud, seem to show that these thickenings do not exert any influence on the growth pattern of the subjacent mesenchyme and do not elicit changes of the normal organogenesis of the experimental bud.