Normal and experimental variations in proportions of skeleton of chick embryo wing

Abstract

THE precise control of symmetry between left and right paired skeletal elements of the developing chick embryo can be exploited in a sensitive test of the effect of unilateral experimental perturbation^1–4. I report here a modified technique which can be used to detect localised defects without reference to the contralateral side. This can give a clear indication of the teratogenic effect of irradiation and various chemical treatments at doses smaller than those usually necessary to demonstrate such effects. Such experiments are of necessity bilateral in their effect unless laborious interembryonic grafts are performed (C. Tickle, personal communication).