Karl Ernst von Baer Biography (1792-1876)
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.