How studies on the avian embryo have opened new avenues in the understanding of development: A view about the neural and hematopoietic systems

The chick embryo is as ancient a source of knowledge on animal development as the very beginning of embryology. Already, at the time of Caspar Friedrich Wolff, contemplating the strikingly beautiful scenario of the germ deploying on the yellow background of the yolk inspired and supported the tenants of epigenesis at the expense of the preformation theory. In this article, we shall mention some of the many problems of developmental biology that were successfully clarified by research on chick embryos. Two topics, the development of the neural system and that of blood and blood vessels, familiar to the authors, will be discussed in more detail.