![]() He also fused together two identical halves from different embryos and observed formation of the neural plate. Additionally, splitting the embryo in half and rotating the animal pole in respect to the vegetal pole resulted in determination spreading from the lower vegetal pole, where the upper blastopore lip was located, to the upper animal half. Spemann also showed that by transplanting a piece from the upper blastopore lip into an area of presumptive epidermis, a secondary embryonic primordium formed, including a secondary neural tube, notochord and somites. ![]() In 19, Hans Spemann showed that transplanting presumptive epidermis into the area of presumptive neural tissue would change the fate of the transplanted cells to that of their new destination, and likewise when he transplanted presumptive neural tissue to where the presumptive epidermis was forming. ![]() Prior to its discovery, it had been hypothesized by multiple groups that there exists a portion of the developing embryo that serves as an "organization center". The Spemann-Mangold organizer was first described in 1924 by Hans Spemann and Hilde Mangold. This discovery significantly impacted the world of developmental biology and fundamentally changed the understanding of early development. First described in 1924 by Hans Spemann and Hilde Mangold, the introduction of the organizer provided evidence that the fate of cells can be influenced by factors from other cell populations. ![]() Nonetheless, this transplantation approach soon led to a major research program for many embryologists.The Spemann-Mangold organizer is a group of cells that are responsible for the induction of the neural tissues during development in amphibian embryos. Different pieces of tissue seemed to induce different results, and while the Spemann lab catalogued and correlated those effects, it soon became clear that induction was not a simple linear process. As Spemann and others would soon recognize, however, induction was a much broader phenomenon. The ability of the dorsal lip of the blastopore to have this profound effect earned it the title of the “organizer”, or “primary inducer”. The result was spectacular: an entire, second embryo with its own set of differentiated parts was induced in the host blastocoel. But what started the process in the first place? In a particularly revealing experiment published in 1924, Spemann and his student Hilde Proescholdt Mangold (1898-1924), using salamanders, transplanted a portion of the dorsal lip of the blastopore (the region of the gastrula just above the point of invagination) into the blastocoel, or entral cavity of the blastula of a host embryo. His techniques of transplanting embryonic regions from younger to older embryos (or vice-versa) led to the concept of embryonic induction, the process by which previously-differentiated tissues trigger the next stage of differentiation, in a kind of cascade, in the developmental sequence. He was asking fundamental questions about what directs development and differentiation of parts. During this time, Spemann continued his experiments with transplantation of tissues in amphibians (frogs and salamanders). ![]() Spemann had attracted a number of outstanding young biologists to his laboratory, which they recalled as a friendly and open place to work. Hans Spemann, who directed the Zoological Institute at Freiburg that had been established by August Weismann (1834-1914), accepted Hamburger as a graduate student for the year 1920-21. ![]()
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