December 6, 2023

Hans Spemann: discovery of Embryonic induction

Hans Spemann (1869-1941) was a German biologist who is best known for his work on experimental embryology and developing the experimental approach to preformationism”.

In 1902-1903 he helped to isolate the embryonic tissue layer that would later be known as the “neural plate” and in 1909 he discovered a means of germinal induction, which is the method of transforming one type of cell into another.

About Hans Spemann

Hans Spemann was born in Osterode am Harz in Germany on 21 September 1869. He moved to Elberfeld to study medicine at the age of 19, and subsequently he studied biology under Ernst Haeckel at the University of Jena from 1890 to 1900.

Life of Spemann

His birth

He was born in the town of Osterode am Harz, Germany. His parents were Gottlieb Spemann and Rosina Spemann (nee Korn). He had two brothers, Gottfried and Hermann. He was the eldest of the three brothers. Spemann’s father died young, when Hans was only 3. He had to begin working when he was six years old to help support his family. This early experience in work would later have a significant impact on his life and work.

Education of Spemann

He started his education in 1883 at the grammar school of Osterode am Harz. There his father was headmaster, and later in 1890 he went to the Elbefield School. He studied medicine at the University of Jena and he obtained his Doctor of Medicine degree in 1900.

He did his research under Ernst Haeckel from 1890 to 1900, who gave him the opportunity to work in Naples for two years, which probably led to him doing experimental embryology.

Personal Life of Spemann

He married Anna Erika Weigelt in 1899 in Jena, and the couple had four children.

He was a very religious man and was influenced by his father. His father was very religious and his mother was a strong Catholic as well; but he had some doubts about that.

Hans Spemann Career

He returned to Jena in 1900 and got a job as assistant to Ernst Haeckel. Then he moved with Haeckel to Naples for two years. They studied marine animals, and Spemann returned to Jena in 1902.

He then became an assistant professor of zoology at the University of Freiburg im Breisgau. He received his doctorate from the University of Jena in 1900. Then he continued research at Naples for two years with Haeckel. In 1902 he was appointed associate professor of zoology at the University of Freiburg-im-Breisgau , and in 1913 he was transferred to the Albert Ludwig’s University of Freiburg as Professor for Zoology until 1939 when he retired.

Experiments in ontogeny

Spemann’s experiments in embryology were directed at the development of arthropod embryos. He investigated the forms, stages and segmentation processes of these animals, and he postulated that their ontogeny followed an overall plan.

He accepted Haeckel’s theory of recapitulation, and he used the term “preformation” to describe the idea that all tissues are present in an organized state within the embryo. By contrast with his colleague and teacher Haeckel, Spemann was not a believer in Darwin’s theory of evolution. He believed that the embryo recapitulates the history of animal evolution. Spemann’s demonstration that a nerve sheath is formed prior to the formation of the so-called “neural plate” was his major contribution to developmental biology.

He discovered that a nerve cell could transform itself directly into a cardigan into a nerve cell when it was exposed to certain chemicals. The chemical, which he named “Nerve factor”, worked by releasing an enzyme in the cell and inducing it to develop, or differentiate, into another type of cell.

Spemann was one of the most influential experimental embryologists and gained wide recognition for his experiments.

Discovery of Embryonic Induction

Spemann described his first demonstration of the transformation in 1902. He exposed a stage 9 embryo to extract the embryonic area, which is now known as the dorsal lip of the blastopore. The embryo was removed after 24 hours and transferred to fresh sea water. A thin sheet of epithelial cells developed along its surface and soon a small bud could be seen on the surface. When later examined under the microscope, it had two nerve cords, two sets of eyespots, pharyngeal arches, visceral arches and a tail ridge. The embryo was self-regenerating and continued its development until it reached stage 11. Spemann referred to this type of induction of embryonic development as “organizer”, or “founder effect”. 

Elements of Embryogenesis

The main principle of Spemann’s experimental system was that embryogenesis is a developmental process, in which a new animal emerges from a few primordial germ cells which are no longer visible.

Hans Spemann observed that the germ-layer following gastrulation (invagination) forms an embryo with all organs organized into individual segments, and therefore these structures have no function as yet.

Induction and organizers

After Hans Spemann’s discovery, embryologists began to explore the topic of organogenesis. In 1910, his former lab assistant Karl Vogt showed that an organism is present in all animals and becomes active during the later stages of development. This phenomenon was known as the “preformation hypothesis”, according to which new structures are formed in the preformed tissue.

When he discovered this technique of inducing a change in a cell, he made experiments with amphibian embryos (frogs and tadpoles) and mammalian embryos (mice) to see how this might work. He discovered that they had a substance at certain points on their surfaces which could be released when incubated with nerve solutions, or contained by chemicals called nerve factors.

Awards and Hounors

Spemann’s discovery of the induction for organogenesis was a significant contribution to the field of genetics and embryology.

Hans Spemann won many awards, including the Albert Lasker Award in 1946, and the Balzan Prize in 1949. He was a member of several scientific organizations; he also had honorary degrees from several universities. He received an honorary degree from Yale University in New Haven, Connecticut, USA in 1926.

Hans Spemann was elected president of the German Society of Zoologists in 1931-33 and he was vice president of the International Zoological Congress. He also contributed to several journals during his lifetime. He won the Nobel Prize in Medicine in 1950. Spemann was a racist and believed that the Aryan race is superior to other races.

After his death, his colleagues and students felt that his ideas were very important for the field of developmental biology. Some found them “unscientific, but inspired”. The main value of his work was its contribution to organized research, unlike previous ones that were based on chance observation.

However, Spemann’s theory has been criticized as being wrong or incomplete because not all embryos appeared fully formed after inducers were applied. However, according to his theory, this did not matter because it did not have a role yet within the organism.

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