Baer

Karl Ernst von Baer (February 17, 1792 - November 26, 1876) was a Baltic German biologist and a founding father of embryology.
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One of ten children, Von Baer was born in Piep, Estonia, to parents descendedfrom Prussian nobility. Due to the large size of his family, he was sent tolive with his childless uncle and aunt until the age of seven. Initially tutored at home, he later spent three years at a school for the children of nobility. Although his father and uncle encouraged him to pursue a military career, from 1810-1814, Von Baer attended the University of Dorpat in Vienna, Austria and obtained an MD degree. From 1814-1817, he studied comparative anatomyat Würzburg. In 1817, he was appointed prosector at the University of Königsberg, where in 1819, he accepted an appointment to teach zoology andanatomy and serve as chief at the new zoological museum that he organized. In 1828, he became a member of the St. Petersburg Academy of Sciences, where he taught zoology from 1829-30. He then returned to Königsberg until 1834. At that time, he became librarian at St. Petersburg Academy of Sciences, and conducted research in anatomy and zoology. In 1846, he was also appointed to the position of Professor of Comparative Anatomy and Physiology at the Medico-Chirugical Academy in St. Petersburg.
Von Baer also took part in other types of scientific projects. In 1837, he led a scientific expedition to Novaya Zemlya in Arctic Russia, and from 1851-6,studied the fisheries of lake Peipus and the Baltic and Caspian Seas. He served as inspector of fisheries for the empire from 1851-1852. He founded the St. Petersburg Society for Geography and Ethnography and the German Anthropological Society. Von Baer died in Dorpat, Estonia, on November 28, 1876.
Von Baer made significant contributions to the world of science. The first ofBaer's most famous discoveries grew out of his work at Königsberg. Formore than a century, scientists had attempted to determine the exact nature and location of the mammalian egg. In 1673, Regnier de Graaf had discovered follicles in the ovaries that he thought might be eggs. However, he later foundstructures even smaller than follicles in the uterus, raising doubts about the role of the follicles themselves. During his research at Königsberg,Baer discovered the mammalian egg by identifying a yellowish spot within thefollicle visible only with a microscope. He developed this idea in his 1827 treatise, De ovi mammalium et hominis genesi (On the Origin of the Mammalian and Human Ovum).
Baer's second great accomplishment was his explanation of early embryonic development, a theory that he summarized in his two-volume textbook Überdie Entwicklunggeschichte der Thiere (On the Development of Animals), 1828-1837. Here he set forth the theory that embryos of all animals begin as similar structures that are both simple and homogeneous and develop intocomplex heterogeneous forms. In fact, he said, it is impossible to distinguish among the early embryos of birds, reptiles, and mammals until their laterstages of development. He set forth the germ-layer theory of development which stated that during the early stages of development, embryos ultimately formfour (later shown to be three) distinct layers that eventually differentiateinto specific organs or body structures. These are the ectoderm, mesoderm and endoderm. While observing embryos, Von Baer discovered the extraembryonic membranes, the chorion, amnion, and allantois and determined their functions.He also discovered the presence of a notochord in early vertebrate embryos. Although the notochord quickly changes into a spinal column, its early presence indicates the evolutionary connection between vertebrates and other organisms now classified together in the phylum chordata. For his work, Von Baer was awarded the Copley Medal of the Royal Society in 1876.

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Karl Ernst von Baer (February 17, 1792 - November 26, 1876) was a Baltic German biologist and a founding father of embryology.
1 Life
2 Contributions
2.1 Embryology
2.2 Baer's laws
2.3 Anthropology
2.4 Baer's law
2.5 Explorer
2.6 Entomology
2.7 Subjective biology
3 References
4 External links
5 Further reading
Life
Karl Ernst von Baer was born in Piibe manor (German: Piep), Estonia; many of his ancestors had come from Westphalia. A knight by birthright, his full name was Karl Ernst Ritter von Baer, Edler von Huthorn. He was educated at the Cathedral School in Reval (Tallinn) and the University of Dorpat (Tartu). He continued his education in Berlin, Vienna, and Würzburg where Döllinger introduced him to the new field of embryology.
In 1812, Baer was a volunteer in the war against Napoleon's invasion, serving as doctor[1].
In 1817, he became a professor at Königsberg University (Kaliningrad) and full professor of zoology in 1821, and of anatomy in 1826. In 1829 he taught briefly in St Petersburg, but returned to Königsberg. In 1834 Baer moved back to St Petersburg and joined the St Petersburg Academy of Sciences, first in zoology (1834-46) and then in comparative anatomy and physiology (1846-62). His interests while there were anatomy, ichthyology, ethnography, anthropology and geography. The last years of his life (1867-76) were spent in Dorpat (Tartu), where he became one of the leading critics of the theories of Charles Darwin.
A statue honouring him can be found on Toome Hill (Toomemägi) in Tartu. The two kroons (2 krooni) Estonian banknote bears his portrait.

Contributions
Embryology
He studied the embryonal development of animals, discovering the blastula stage of development and the notochord. Together with Heinz Christian Pander and based on the work by Caspar Friedrich Wolff he described the germ layer theory of development (ectoderm, mesoderm, and endoderm) as a principle in a variety of species laying the foundation for comparative embryology in the book Über Entwickelungsgeschichte der Thiere (1828). In 1826 Baer discovered the mammalian ovum. The first human ovum was described by Allen in 1928.(1) In 1827 he completed research "Ovi Mammalium et Hominis genesi" for Saint-Petersburg's Academy of Science (published at Leipzig[2][3]) and established that mammals develop from eggs.
Baer's laws
He formulated what would later be called the Baer's laws for embryology:
The general characters of the group to which an embryo belongs appear in development earlier than the special characters.
The less general structural relations are formed after the more general, and so on, until the most specific appear.
The embryo of any given form, instead of passing through the state of other definite forms, on the contrary, separates itself from them.
Fundamentally the embryo of a higher animal form never resembles the adult of another animal form, but only its embryo.
See also: Recapitulation theory
In old age
Anthropology
At St Petersburg, Baer established an extensive skull collection and became a proponent and contributor to the (pseudo)science of craniology.
Baer's law
The term Baer's law also refers to the proposition that in the northern hemisphere, erosion occurs mostly on the right banks of rivers, and in the southern hemisphere on the left banks.
Explorer
Baer was interested in the Northern part of Russia and explored Novaya Zemlya in 1837 collecting biologic specimen. Other travels led him to the Caspian Sea, the North Cape, and Lapland. He was a founder and the first president of the Russian Geographical Society.
Entomology
Baer contributed to studies in entomology and was a cofounder of the Russian Entomological Society.
Subjective biology
Baer was a pioneer in studying biological time - the perception of time in different organisms. This approach was further developed by Jakob von Uexküll.
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References
Wood C, Trounson A. Clinical In Vitro Fertilization. Springer-Verlag, Berlin 1984, Page 6.
Medical eponyms
Baer, K E v. "Über ein allgemeines Gesetz in der Gestaltung der Flußbetten", Kaspische Studien, 1860, VIII, S. 1–6.