Johannes Peter Müller
Johannes Peter Müller was a German physiologist, comparative anatomist and herpetologist, known not only for his discoveries but for his ability to synthesize knowledge. Müller was born in Koblenz, he was the son of a poor shoemaker, was about to be apprenticed to a saddler when his talents attracted the attention of his teacher, he prepared himself to become a Roman Catholic Priest. During his college course at Koblenz, he devoted himself to the classics and made his own translations of Aristotle. At first, his intention was to become a priest; when he was 18 though, his love for natural science became dominant, he turned to medicine, entering the University of Bonn in 1819. There he received his M. D.. He studied at Berlin. There, under the influence of Hegel and Rudolphi, he was induced to reject all systems of physiology which were not founded upon a strict observation of nature, he became Privatdozent of physiology and comparative anatomy at Bonn in 1824, extraordinary professor of physiology in 1826, ordinary professor in 1830.
In 1833 he went to the Humboldt University of Berlin, where he filled the chair of anatomy and physiology until his death. Müller made contributions in numerous domains of physiology, in particular increasing understanding of the voice and hearing, as well as the chemical and physical properties of lymph and blood, his first important works, Zur vergleichenden Physiologie des Gesichtssinns and Über die phantastischen Gesichtserscheinungen, are of a subjective philosophical tendency. The first work concerns the most important facts as to human and animal sight, the second sounds depths of difficult psychological problems, he soon became the leader in the science of the morphological treatment of zoology as well as of experimental physiology. To his research is due the settlement of the theory of reflex action. In the century preceding Müller's work, many contributions to physiological science had been made. Müller gave order to these facts, developed general principles and showed physiologists how recent discoveries in physics and chemistry could be applied to their work.
The appearance of his magnum opus, Handbuch der Physiologie des Menschen, between 1833 and 1840 marked the beginning of a new period in the study of physiology. In it, for the first time, the results of human and comparative anatomy, as well as of chemistry and other departments of physical science, tools like the microscope, were brought to bear on the investigation of physiological problems; the most important portion of the work was that dealing with nervous action and the mechanism of the senses. Here he stated the principle recognized but not stated as that the kind of sensation following stimulation of a sensory nerve does not depend on the mode of stimulation but upon the nature of the sense organ, thus light, pressure, or mechanical stimulation acting on the retina and optic nerve invariably produces luminous impressions. This he termed the law of specific energies of the sense; the book became the leading textbook in physiology for much of the nineteenth century. It manifests Müller’s interests in vitalism and scientific rigor.
He discusses the difference between organic matter. He considers in detail various physiological systems of a wide variety of animals, but attributes the indivisible whole of an organism to the presence of a soul, he proposes that living organisms possess a life-energy for which physical laws can never account. Edward Forbes F. R. S. in his A History of British Starfishes, Other Animals of the Class Echinodermata in his preface refers to Muller as the "one of the greatest living physiologists, Muller of Berlin". In the part of his life he chiefly devoted himself to comparative anatomy. Fishes and marine invertebrata were his favorite subjects, he took 19 trips to the Baltic and North Sea, the Adriatic and the Mediterranean to investigate salt-water life. He authored a comprehensive work on the anatomy of amphibians, he described several new species of snakes. Müller mentored such distinguished scientists and physiologists as Hermann von Helmholtz, Emil du Bois-Reymond, Theodor Schwann, Friedrich Gustav Jakob Henle, Carl Ludwig and Ernst Haeckel.
In 1834, he was elected a foreign member of the Royal Swedish Academy of Sciences. Müller died in Berlin in 1858. In 1899, a bronze statue by Joseph Uphues was erected in his memory at Koblenz. In addition to his Handbuch der Physiologie, his publications include: De Respiratione Fœtus, a prize dissertation Zur vergleichenden Physiologie des Gesichtssinns Über die phantastischen Gesichtserscheinungen Bildungsgeschichte der Genitalien, in which he traced the development of the Müllerian duct De glandularum secernentium structura penitiori Beiträge zur Anatomie und Naturgeschichte der Amphibien Der Tabak in geschichtlicher, chemischer und medizinischer Hinsicht Vergleichende Anatomie der Myxinoiden Ueber die organischen Nerven der erectilen männlichen Geschlechtsorgane... Ueber den feineren Bau der krankhaften Geschwülste, unfinished — a pioneering use of microscopical research in the investigation of pathological anatomy Systematische Beschreibung der Plagiostomen with F. G. J. Henle System der Asteriden.
Braunschweig: Friedrich Vieweg und Sohn. with F. H. Troschel Horae
Ferdinand Georg Frobenius
Ferdinand Georg Frobenius was a German mathematician, best known for his contributions to the theory of elliptic functions, differential equations, number theory, to group theory. He is known for the famous determinantal identities, known as Frobenius–Stickelberger formulae, governing elliptic functions, for developing the theory of biquadratic forms, he was the first to introduce the notion of rational approximations of functions, gave the first full proof for the Cayley–Hamilton theorem. He lent his name to certain differential-geometric objects in modern mathematical physics, known as Frobenius manifolds. Ferdinand Georg Frobenius was born on 26 October 1849 in Charlottenburg, a suburb of Berlin from parents Christian Ferdinand Frobenius, a Protestant parson, Christine Elizabeth Friedrich, he entered the Joachimsthal Gymnasium in 1860. In 1867, after graduating, he went to the University of Göttingen where he began his university studies but he only studied there for one semester before returning to Berlin, where he attended lectures by Kronecker and Karl Weierstrass.
He received his doctorate in 1870 supervised by Weierstrass. His thesis, supervised by Weierstrass, was on the solution of differential equations. In 1874, after having taught at secondary school level first at the Joachimsthal Gymnasium at the Sophienrealschule, he was appointed to the University of Berlin as an extraordinary professor of mathematics. Frobenius was only in Berlin a year before he went to Zürich to take up an appointment as an ordinary professor at the Eidgenössische Polytechnikum. For seventeen years, between 1875 and 1892, Frobenius worked in Zürich, it was there that he married, brought up his family, did much important work in differing areas of mathematics. In the last days of December 1891 Kronecker died and, his chair in Berlin became vacant. Weierstrass believing that Frobenius was the right person to keep Berlin in the forefront of mathematics, used his considerable influence to have Frobenius appointed. In 1893 he returned to Berlin. Group theory was one of Frobenius' principal interests in the second half of his career.
One of his first contributions was the proof of the Sylow theorems for abstract groups. Earlier proofs had been for permutation groups, his proof of the first Sylow theorem is one of those used today. Frobenius has proved the following fundamental theorem: If a positive integer n divides the order |G| of a finite group G the number of solutions of the equation xn = 1 in G is equal to kn for some positive integer k, he posed the following problem: If, in the above theorem, k = 1 the solutions of the equation xn = 1 in G form a subgroup. Many years ago this problem was solved for solvable groups. Only in 1991, after the classification of finite simple groups, this problem was solved in general. More important was his creation of the theory of group characters and group representations, which are fundamental tools for studying the structure of groups; this work led to the notion of Frobenius reciprocity and the definition of what are now called Frobenius groups. A group G is said to be a Frobenius group if there is a subgroup H < G such that H ∩ H x = for all x ∈ G − H.
In that case, the set N = G − ⋃ x ∈ G − H H x together with the identity element of G forms a subgroup, nilpotent as John G. Thompson showed in 1959. All known proofs of that theorem make use of characters. In his first paper about characters, Frobenius constructed the character table of the group P S L of order for all odd primes p, he made fundamental contributions to the representation theory of the symmetric and alternating groups. Frobenius introduced a canonical way of turning primes into conjugacy classes in Galois groups over Q. If K/Q is a finite Galois extension to each prime p which does not ramify in K and to each prime ideal P lying over p in K there is a unique element g of Gal satisfying the condition g = xp for all integers x of K. Varying P over p changes g into a conjugate, so the conjugacy class of g in the Galois group is canonically associated to p; this is called the Frobenius conjugacy class of p and any element of the conjugacy class is called a Frobenius element of p.
If we take for K the mth cyclotomic field, whose Galois group over Q is the units modulo m for p not dividing m the Frobenius class in the Galois group is p mod m. From this point of view, the distribution of Frobenius conjugacy classes in Galois groups over Q generalizes Dirichlet's classical result about primes in arithmetic progressions; the study of Galois groups of infinite-degree extensions of Q depends crucially on this construction of Frobenius elements, which provides in a sense a dense subset of elements which are accessible to detailed study. List of things named after Ferdinand Georg Frobenius Frobenius, Ferdinand Georg, Serr
A germ layer is a primary layer of cells that forms during embryonic development. The three germ layers in vertebrates are pronounced; some animals, like cnidarians, produce two germ layers making them diploblastic. Other animals such as chordates produce a third layer, between these two layers. Making them triploblastic. Germ layers give rise to all of an animal’s tissues and organs through the process of organogenesis. Caspar Friedrich Wolff observed organization of the early embryo in leaf-like layers. In 1817, Heinz Christian Pander discovered three primordial germ layers while studying chick embryos. Between 1850 and 1855, Robert Remak had further refined the germ cell layer concept, stating that the external and middle layers form the epidermis, the gut, the intervening musculature and vasculature; the term "mesoderm" was introduced into English by Huxley in 1871, "ectoderm" and "endoderm" by Lankester in 1873. Among animals, sponges show the simplest organization. Although they have differentiated cells, they lack true tissue coordination.
Diploblastic animals and Ctenophora, show an increase in complexity, having two germ layers, the endoderm and ectoderm. Diploblastic animals are organized into recognisable tissues. All higher animals are triploblastic, possessing a mesoderm in addition to the germ layers found in Diploblasts. Triploblastic animals develop recognizable organs. Fertilization leads to the formation of a zygote. During the next stage, mitotic cell divisions transform the zygote into a hollow ball of cells, a blastula; this early embryonic form undergoes gastrulation, forming a gastrula with either two or three layers. In all vertebrates, these progenitor cells differentiate into all adult organs. In the human embryo, after about three days, the zygote forms a solid mass of cells by mitotic division, called a morula; this changes to a blastocyst, consisting of an outer layer called a trophoblast, an inner cell mass called the embryoblast. Filled with uterine fluid, the blastocyst breaks out of the zona pellucida and undergoes implantation.
The inner cell mass has two layers: the hypoblast and epiblast. At the end of the second week, a primitive streak appears; the epiblast in this region moves towards the primitive streak, dives down into it, forms a new layer, called the endoderm, pushing the hypoblast out of the way The epiblast keeps moving and forms a second layer, the mesoderm. The top layer is now called the ectoderm; the endoderm is one of the germ layers formed during animal embryonic development. Cells migrating inward along the archenteron form the inner layer of the gastrula, which develops into the endoderm; the endoderm consists at first of flattened cells. It forms the epithelial lining of the whole of the digestive tract except part of the mouth and pharynx and the terminal part of the rectum, it forms the lining cells of all the glands which open into the digestive tract, including those of the liver and pancreas. The endoderm forms: the pharynx, the esophagus, the stomach, the small intestine, the colon, the liver, the pancreas, the bladder, the epithelial parts of the trachea and bronchi, the lungs, the thyroid, the parathyroid.
The mesoderm germ layer forms in the embryos of triploblastic animals. During gastrulation, some of the cells migrating inward contribute to the mesoderm, an additional layer between the endoderm and the ectoderm; the formation of a mesoderm leads to the development of a coelom. Organs formed inside a coelom can move and develop independently of the body wall while fluid cushions and protects them from shocks; the mesoderm has several components which develop into tissues: intermediate mesoderm, paraxial mesoderm, lateral plate mesoderm, chorda-mesoderm. The chorda-mesoderm develops into the notochord; the intermediate mesoderm develops into gonads. The paraxial mesoderm develops into cartilage, skeletal muscle, dermis; the lateral plate mesoderm develops into the circulatory system, the wall of the gut, wall of the human body. Through cell signaling cascades and interactions with the ectodermal and endodermal cells, the mesodermal cells begin the process of differentiation; the mesoderm forms: muscle, cartilage, connective tissue, adipose tissue, circulatory system, lymphatic system, genitourinary system, serous membranes, notochord.
The ectoderm generates the outer layer of the embryo, it forms from the embryo's epiblast. The ectoderm develops into the surface ectoderm, neural crest, the neural tube; the surface ectoderm develops into: epidermis, nails, lens of the eye, sebaceous glands, tooth enamel, the epithelium of the mouth and nose. The neural crest of the ectoderm develops into: peripheral nervous system, adrenal medulla, facial cartilage, dentin of teeth; the neural tube of the ectoderm develops into: brain, spinal cord, posterior pituitary, motor neurons, retina. Note: The anterior pituitary develops from the ectodermal tissue of Rathke's pouch; because of its great importance, the neural crest is sometimes considered a fourth germ layer. It is, derived from the ectoderm. Histogenesis
Cell division is the process by which a parent cell divides into two or more daughter cells. Cell division occurs as part of a larger cell cycle. In eukaryotes, there are two distinct types of cell division: a vegetative division, whereby each daughter cell is genetically identical to the parent cell, a reproductive cell division, whereby the number of chromosomes in the daughter cells is reduced by half to produce haploid gametes. Meiosis results in four haploid daughter cells by undergoing one round of DNA replication followed by two divisions. Homologous chromosomes are separated in the first division, sister chromatids are separated in the second division. Both of these cell division cycles are used in the process of sexual reproduction at some point in their life cycle. Both are believed to be present in the last eukaryotic common ancestor. Prokaryotes undergo a vegetative cell division known as binary fission, where their genetic material is segregated into two daughter cells. All cell divisions, regardless of organism, are preceded by a single round of DNA replication.
For simple unicellular microorganisms such as the amoeba, one cell division is equivalent to reproduction – an entire new organism is created. On a larger scale, mitotic cell division can create progeny from multicellular organisms, such as plants that grow from cuttings. Mitotic cell division enables sexually reproducing organisms to develop from the one-celled zygote, which itself was produced by meiotic cell division from gametes. After growth, cell division by mitosis allows for continual repair of the organism; the human body experiences about 10 quadrillion cell divisions in a lifetime. The primary concern of cell division is the maintenance of the original cell's genome. Before division can occur, the genomic information, stored in chromosomes must be replicated, the duplicated genome must be separated cleanly between cells. A great deal of cellular infrastructure is involved in keeping genomic information consistent between generations. Interphase is the process a cell must go through before mitosis and cytokinesis.
Interphase consists of three main stages: G1, S, G2. G1 is a time of growth for the cell where specialized cellular functions occur in order to prepare the cell for DNA Replication. There are checkpoints during interphase that allow the cell to be either progressed or denied further development. In S phase, the chromosomes are replicated in order for the genetic content to be maintained. During G2, the cell undergoes the final stages of growth before it enters the M phase, where spindles are synthesized; the M phase, can be either meiosis depending on the type of cell. Germ cells, or gametes, undergo meiosis. After the cell proceeds through the M phase, it may undergo cell division through cytokinesis; the control of each checkpoint is controlled by cyclin and cyclin dependent kinases. The progression of interphase is the result of the increased amount of cyclin; as the amount of cyclin increases and more cyclin dependent kinases attach to cyclin signaling the cell further into interphase. The peak of the cyclin attached to the cyclin dependent kinases this system pushes the cell out of interphase and into the M phase, where mitosis and cytokinesis occur.
There are three transition checkpoints. The most important being the G1-S transition checkpoint. If the cell does not pass this phase the cell will most not go through the rest of the cell division cycle. Prophase is the first stage of division; the nuclear envelope is broken down, long strands of chromatin condense to form shorter more visible strands called chromosomes, the nucleolus disappears, microtubules attach to the chromosomes at the kinetochores present in the centromere. Microtubules associated with the alignment and separation of chromosomes are referred to as the spindle and spindle fibers. Chromosomes will be visible under a microscope and will be connected at the centromere. During this condensation and alignment period, homologous over. In metaphase, the centromeres of the chromosomes convene themselves on the metaphase plate, an imaginary line, equidistant from the two centrosome poles. Chromosomes line up in the middle of the cell by MTOCs by pushing and pulling on centromeres of both chromatids which causes the chromosome to move to the center.
The chromosomes are still condensing and are at one step away from being the most coiled and condensed they will be. Spindle fibres have connected to the kinetochores. At this point, the chromosomes are ready to split into opposite poles of the cell towards the spindle to which they are connected. Anaphase is a short stage of the cell cycle and occurs after the chromosomes align at the mitotic plate. After the chromosomes line up in the middle of the cell, the spindle fibers will pull them apart; the chromosomes are split apart as the sister chromatids move to opposite sides of the cell. While the sister chromatids are being pulled apart and plasma gets elongated from non-kinetochore microtubules Telophase is the last stage of the cell cycle. A cleavage furrow splits the cell in two; these two cells form around the chromatin at the two poles of the cell. Two nuclear membranes begin to reform and the chromatin begin to unwind. Cells are broadly classified into two main categories: simple, non-nucleated prokaryotic cells, complex, nucleated eukaryotic cells.
Owing to their structural differences and prokaryotic cells do not divide in the same way. The pattern of cell division that tr
Bad Kissingen is a spa town in the Bavarian region of Lower Franconia and seat of the district Bad Kissingen. Situated to the south of the Rhön Mountains on the Franconian Saale river, it is one of the health resorts, which became famous as a "Weltbad" in the 19th century; the town was first documented in the year 801 as chizzicha and was renowned above all for its mineral springs, which are recorded from as early as 823. At that time Kissingen was under the domination of Fulda Abbey it fell to the Counts of Henneberg and was sold to the bishops of Würzburg in the 14th century. Kissingen was first mentioned as "oppidum" in 1279; the town developed to a spa in the 1500s and recorded its first official spa guest in 1520. In 1814 Kissingen became part of Bavaria; the town grew to be a fashionable resort in the 19th century, was extended during the reign of Ludwig I of Bavaria. Crowned heads of state such as Empress Elisabeth of Austria, Tsar Alexander II of Russia and King Ludwig II of Bavaria, who bestowed the'Bad' on Kissingen in 1883, were among the guests of the spa at this time.
Other well-known visitors to the resort included author Leo Tolstoy, composer Gioachino Rossini and artist Adolph von Menzel. On 10 July 1866 during the Mainfeldzug of the Austro-Prussian War, Kissingen was the site of fierce battle between Bavarian and Prussian troops, which ended with a Prussian victory. Imperial Chancellor Otto von Bismarck visited Kissingen's spas many times, in 1874 in the course of the Kulturkampf he survived an assassination attempt by the catholic Eduard Franz Ludwig Kullmann there. In 1877 the Kissingen Dictation was written here, in which Bismarck explained the principles of his foreign policy. Bismarck’s former home in Kissingen is now the Bismarck Museum. In June 1911 Alfred von Kiderlen-Waechter, German Secretary of State, the French ambassador Jules Cambon had negotiations in Bad Kissingen about Morocco without achieving a solution; the failure of the negotiations lead to the Agadir Crisis. The resort's clientele changed in the 20th century, with ordinary people replacing nobility as guests.
The spa suffered a one-year interruption in the only closure in its history. Shortly prior to World War II Manteuffel Kaserne was established at the eastern edge of the Bad Kissingen town center by the German military as part of Hitler's program to expand the German Wehrmacht. In 1945, the American military entered the town peacefully, took over the Kaserne, renamed Daley Barracks in 1953; the barracks were closed in the 1990s after the fall of the iron curtain when the American troops were withdrawn. After the war, the Department of Social Security built clinics in the town. A change in health legislation in the 1990s reduced the opportunities for German health insurance contracts to fund spa visits, which led to job losses; as a result, efforts were made to attract a new kind of clientele, helped in no small part by the EMNID survey which named Bad Kissingen Germany’s best-known spa town. In 2015, about 1.5 million overnight stays of more than 238 000 visitors were registered in the town. With the opening of the KissSalis Therme in February 2004, Bad Kissingen gained a spa leisure centre, in December 2004, the German-Chinese Football Academy was opened in the town, where the Chinese "08 Star Team" lived and trained in preparation for the Olympic Games in Beijing in 2008.
Bad Kissingen was one of the leading spas in the 19th and early 20th century, which in German are called "Weltbad". They differ from other spa resorts through the following criteria: Entertainment: The social life in a "Weltbad" is at least as important as the medical cure, or more. A "Weltbad" offered many opportunities for the spa guests to spend their free time, such as exercise and sports, trips to the surroundings and concert, library and games. Guests: The "Weltbad" was attractive to guests from all five continents. Particular attention was paid to prominent visitors, who attracted more visitors from nobility and upscale middle class. Architecture: There are spa quarter, quarters with villas, areas for business and care and parks with a smooth transition into the surrounding landscape Infrastructure and supply: Despite the small number of inhabitants, a "Weltbad" offered the guests all the contemporary comfort, not common in all major cities; these include good transport connections, communication facilities, luxury goods offer, differentiated hotel and gastronomy as well as state-of-the-art technology for energy supply, water supply and sanitation.
Bad Kissingen and several other of these traditional spa baths want to become a UNESCO World Heritage site under the name "Great Spas of Europe". In addition to the main town of Bad Kissingen, its districts include: Albertshausen Arnshausen Bad Kissingen Garitz Hausen Kleinbrach Poppenroth Reiterswiesen Winkels Franz Meinow:, 1945–1946 Franz Rothmund: 1946–1947 Karl Fuchs:, 1947–1952 Hans Weiß, 1952–1984 Georg Straus, 1984–1990 Christian Zoll:, 1990–2002 Karl Heinz Laudenbach: 2002–2008 Kay Blankenburg:, since 2008 The Council of Bad Kissingen consists of: The mayor Kay Blankenburg 10 members of the Christian Social Union of Bavaria, 9 members of the Social Democratic Party of Germany, 5 members of the DBK, 3 members of the Freie Wähler party, 2 members of the BfU/Alliance'90/The Greens/ödp 1 member of the Free Democrats. In addition there is one representat
National Library of the Czech Republic
The National Library of the Czech Republic is the central library of the Czech Republic. It is directed by the Ministry of Culture; the library's main building is located in the historical Clementinum building in Prague, where half of its books are kept. The other half of the collection is stored in the district of Hostivař; the National Library is the biggest library in the Czech Republic, in its funds there are around 6 million documents. The library has around 60,000 registered readers; as well as Czech texts, the library stores older material from Turkey and India. The library houses books for Charles University in Prague; the library won international recognition in 2005 as it received the inaugural Jikji Prize from UNESCO via the Memory of the World Programme for its efforts in digitising old texts. The project, which commenced in 1992, involved the digitisation of 1,700 documents in its first 13 years; the most precious medieval manuscripts preserved in the National Library are the Codex Vyssegradensis and the Passional of Abbes Kunigunde.
In 2006 the Czech parliament approved funding for the construction of a new library building on Letna plain, between Hradčanská metro station and Sparta Prague's football ground, Letná stadium. In March 2007, following a request for tender, Czech architect Jan Kaplický was selected by a jury to undertake the project, with a projected completion date of 2011. In 2007 the project was delayed following objections regarding its proposed location from government officials including Prague Mayor Pavel Bém and President Václav Klaus. Plans for the building had still not been decided in February 2008, with the matter being referred to the Office for the Protection of Competition in order to determine if the tender had been won fairly. In 2008, Minister of Culture Václav Jehlička announced the end of the project, following a ruling from the European Commission that the tender process had not been carried out legally; the library was affected by the 2002 European floods, with some documents moved to upper levels to avoid the excess water.
Over 4,000 books were removed from the library in July 2011 following flooding in parts of the main building. There was a fire at the library in December 2012. List of national and state libraries Official website
Karl Ernst von Baer
Karl Ernst Ritter von Baer Edler von Huthorn was a Baltic German scientist and explorer. Baer is known in Russia as Karl Maksímovich Ber. Baer was a naturalist, geologist, geographer, a founding father of embryology, he was an explorer of European Scandinavia. He was a member of the Russian Academy of Sciences, a co-founder of the Russian Geographical Society, the first president of the Russian Entomological Society, making him a distinguished Baltic German scientist. Karl Ernst von Baer was born into the Baltic German noble Baer family in the Piep Manor, Jerwen County, Governorate of Estonia, as a knight by birthright, his family was of Westphalian origin and originated in Osnabrück. He spent his early childhood at Lasila Estonia. Many of his ancestors had come from Westphalia, he was educated at the Knight and Cathedral School in Reval and the Imperial University of Dorpat, each of which he found lacking in quality education. In 1812, during his tenure at the university, he was sent to Riga to aid the city after Napoleon's armies had laid siege to it.
As he attempted to help the sick and wounded, he realized that his education at Dorpat had been inadequate, upon his graduation, he notified his father that he would need to go abroad to "finish" his education. In his autobiography, his discontent with his education at Dorpat inspired him to write a lengthy appraisal of education in general, a summary that dominated the content of the book. After leaving Tartu, he continued his education in Berlin, Würzburg, where Ignaz Döllinger introduced him to the new field of embryology. In 1817, he became a professor at Königsberg University and full professor of zoology in 1821, of anatomy in 1826. In 1829, he taught 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 and in comparative anatomy and physiology, his interests while there were anatomy, ethnography and geography. While embryology had kept his attention in Königsberg in Russia von Baer engaged in a great deal of field research, including the exploration of the island Novaya Zemlya.
The last years of his life were spent in Dorpat. Von Baer studied the embryonic 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 as a principle in a variety of species, laying the foundation for comparative embryology in the book Über Entwickelungsgeschichte der Thiere. In 1826, Baer discovered the mammalian ovum; the human ovum was first described by Edgar Allen in 1928. In 1827, he completed research Ovi Mammalium et Hominis genesi for St Petersburg's Academy of Science. In 1827 von Baer became the first person to observe human ova. Only in 1876 did Oscar Hertwig prove that fertilization is due to fusion of an egg and sperm cell.von Baer formulated what became known as Baer's laws of embryology: General characteristics of the group to which an embryo belongs develop before special characteristics. General structural relations are formed before the most specific appear.
The form of any given embryo does not converge upon other definite forms, but separates itself from them. The embryo of a higher animal form never resembles the adult of another animal form, such as one less evolved, but only its embryo. From his studies of comparative embryology, Baer had believed in the transmutation of species but rejected in his career the theory of natural selection proposed by Charles Darwin, he produced an early phylogenetic tree revealing the phylogeny of vertebrate embryos. In the fifth edition of On the Origin of Species published in 1869, Charles Darwin added a Historical Sketch giving due credit to naturalists who had preceded him in publishing the opinion that species undergo modification, that the existing forms of life have descended by true generation from pre-existing forms. According to Darwin: "Von Baer, towards whom all zoologists feel so profound a respect, expressed about the year 1859... his conviction, chiefly grounded on the laws of geographical distribution, that forms now distinct have descended from a single parent-form."Baer believed in a teleological force in nature which directed evolution.
The term Baer's law is applied to the unconfirmed proposition that in the Northern Hemisphere, erosion occurs on the right banks of rivers, in the Southern Hemisphere on the left banks. In its more thorough formulation, which Baer never formulated himself, the erosion of rivers depends on the direction of flow, as well. For example, in the Northern Hemisphere, a section of river flowing in a North-South direction, according to the theory, erodes on its right bank due to the coriolis effect, while in an East-West section there is no preference. However, this was repudiated by Albert Einstein's Tea leaf paradox. Baer was interested in the northern part of Russia, explored Novaya Zemlya in 1837, collecting biological specimens. Other travels led him to the Caspian Sea, the North Cape, Lapland, he was one of the founders of the Russian Geographical Society. He was a pioneer in studying biological time – the perception of time in different organisms. In 1849, he was elected a foreign honorary of the American Academy of Sciences.
He was elected a