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Karl Ernst von Baer

Born  1792
Died  1876

Related eponyms

Prussian-Estonian biologist, embryologist, anthropologist, and geographer, born February 29, 1792, Piep, near Jerwen, Estonia, Russian Empire; died November 28, 1876, Dorpat (Now Tartu), Estonia.

Biography of Karl Ernst von Baer

His full name is:
Karl Ernst Ritter von Baer, Edler von Huthorn.

Karl Ernst von Baer discovered the mammalian ovum and the notochord and established the new science of comparative embryology alongside comparative anatomy. His most important work is his treatise Ueber die Entwicklungsgeschichte der Thiere, Beobachtung und Reflexion (1828, 1837) the publication of which provided a basis for the systematic study of animal development. He was also a pioneer in geography, ethnology, and physical anthropology.

Early life
Baer descended from an originally Prussian family. One of his ancestors, Andreas Baer, emigrated from Westphalia to Reval, Livonia, in the mid-sixteenth century. A collateral descendant of Andreas bought an estate in Estonia during the mid-seventeenth century, and was made a member of the nobility. Karl's father, Magnus Johann von Baer, was an Estonian landholder whose estate, Piep (Piibe), Jerwen County (Järvamaa) in the Russian Baltic province, was modest in size. His father had been trained in law and, after Karl's birth, served a term as district official - Landrat - and as an official of the Estonian Knighthood, in which the family had gained membership during the late eighteenth century.

Magnus Johann von Baer married his first cousin Juliane Louise von Baer. Karl was one of ten children, of whom three were sons. Because of the large size of the family, his parents entrusted Karl during his early years to his father's brother Karl and his wife, Baroness Ernestine von Canne, from Coburg, who lived on the neighbouring estate Lassila (Lasila) and were childless. Here Karl acquired the love of plants that late drew his interest to botany and natural history.

At the age of seven he returned to his own family. After private tutoring in their home, Baer spent three years (1807-1810) at a cathedral school for members of the nobility in Reval (Tallinn), in order to prepare himself for a military career. However, neither shining swords nor farting horses could stop his interest from changing to the natural sciences. When Karl decided to enter the university, his father encouraged him to go to Germany, but he insisted on entering the University of Dorpat opened six years earlier. He matriculated in August 1810 as a medical student at Dorpat, where he was especially attracted by the lectures of the professor of physiology, Karl Friedrich Burdach (1776-1847) and G. F. Parrot.

Baer's greatest interests were in botany, physics, and physiology. He was conferred doctor of medicine on August 29 (September 10), 1814. Dissatisfied with his medical training, he left Dorpat for further studies in Germany and Austria from 1814 to 1817. He spent the years of 1814 and 1815 in Berlin and Vienna, but the crucial year of his education was the academic year 1815-16. That year he trained in comparative anatomy at the University of Würzburg with Ignaz Döllinger (1770-1841), acquiring preparation skills and the interest in anatomy and developmental problems. Döllinger, one of the great teachers of the nineteenth century, introduced him to a new world that included the study of embryology.

In 1816 Burdach invited Baer to Königsberg (Kaliningrad). During the winter of 1816/1817 von Baer stayed in Berlin to visit several clinics as well as training in practical anatomy. At various times during his years at Königsberg he taught zoology, anatomy, and anthropology. Baer founded a zoological museum, acted several times as director of the botanical gardens, and served terms as dean of the medical faculty and as rector of the university.

In 1819 Baer was elected extraordinary professor of anatomy at the Königsberg University, and in 1821 full professor of zoology, from 1826 also of anatomy. Baer took active part in the social life in Prussia. From 1821 he was the director of the Zoological Museum of Königsberg, which he himself had established.

On January 1, 1820 he married Auguste von Medem of Königsberg, by whom he had six children, five sons and a daughter. The first son died in childhood; the second, Karl, who was interested in natural history, died of typhus at the age of twenty-one while a student at the University of Dorpat.

The Russian connection
Although Baer reached the Peak of his career as an embryologist when at Königsberg, he was restless, and for reasons not yet fully understood, he was unwilling to remain there. He was elected a corresponding member of the Academy of Sciences in St. Petersburg in 1826, and in 1828 he refused an invitation to work at the academy, even though his friend Pander was already there as an academician. In 1829, however, he accepted an invitation to the St. Petersburg Academy, becoming a full academician and director of the zoological museum, but returned after only few months, in 1830, to Königsberg because he disliked the climate and found conditions for work less favourable than in Königsberg.

Königsberg, however, proved no more successful. His hopes for a position at another German university were not fulfilled. When his elder brother Louis, who had been managing the estate at Piep, died in 1834, Baer - through the influence of certain family connections - received a second invitation to St. Petersburg, which he gladly accepted. He then moved to St. Petersburg with his wife and children. His wish to retain the Piep estate for his family and broken health resulting from overwork may have been factors contributing to a move that had not seemed desirable earlier.

Baer became a full member in zoology of the St. Petersburg academy of sciences in 1834, and remained there for the rest of his working life, more than 30 years, "the finery and pride - the soul of the academy".

From Russia with love
Baer's first duties were as librarian of the foreign division, but he eventually served the academy in a variety of administrative positions. First serving in zoology, he in 1846 became academician for comparative anatomy and physiology, and from 1846 to 1852 he served as ordinary professor in those fields at the academy of medicine and surgery in of St. Petersburg. He retired from active membership in 1862 but continued to work as an honorary member until 1867. He then returned to Dorpat.

Baer's change from zoology to anatomy and physiology was motivated by his wish to come closer to anthropology. When he became academician for comparative anatomy and physiology, he took charge of the academy's anatomical museum, a decision related to his long-standing interest in anthropology. His doctoral dissertation in 1814, on diseases endemic among Estonians, was ethnographically inclined. He first lectured on anthropology as early as the winter of his first year in Königsberg (1817-1818), to students of all faculties, not only of medicine. One volume of these lectures was published in 1824; a second, although promised, did not appear.

Particularly interested in the Russian North, in the 1820's, while he was still in Königsberg, Baer had contemplated a trip to Lapland and Novaya Zemlya. After becoming an academician in St. Petersburg, he was able to satisfy his desire for travel, embarking on a career as a courageous explorer. In 1837 he left Archangels for an exploration voyage to Novaya Zemlya, which was then uninhabited, to collect specimens of flora and fauna. In 1845 he visited Trieste, and in the years 1851-1856, on assignment from the government, to investigate the conditions of the fisheries all over the empire: in Paipus, in the Baltic Sea, in the Caspian sea, etc. Besides ha also made lesser journeys to Swedish Lapland, to North Cape (Norway), Germany, and Switzerland.

During his extensive travels throughout Russia, Baer made significant discoveries in geography, including one concerning the nature of the forces responsible for the configuration of the riverbanks in Russia.

Baer's work was of vital importance to the development of Russian science. His work instigated the establishment of the Imperial Russian Geographical and Entomological Society; he gave public lectures on developmental history, but for some reason never continued his embryological investigations from the Königsberg period. He was responsible also for the founding of the Russian Geographical Society, of which he was the first president. From 1839 he was co-editor of and contributor to the important Beiträge zur Kenntniss des Russischen Reiches und der angränzender Länder Asiens.

A matter of skulls
Baer's travels also increased his long-standing interest in ethnography. He contributed to the Academy at St. Petersburg by establishing an extensive skull collection.

Baer classified man into six categories, ranked according to the degree of primitiveness. His interpretations of some peoples as more primitive than others were similar to those of his contemporaries and immediate predecessors; he did not bring to these areas the same vision that he had carried into embryology. Nonetheless, at least one of his contributions to modern anthropology was truly effective.

One of his primary accomplishments, perhaps growing out of his earlier museum experience in Könisgberg, was the establishment at the academy of a craniological collection. Attempts to classify skulls were based on measurements, and Baer thought it desirable that methods of cranial measurements be standardized. To this end, he called together a group of craniologists in Göttingen in 1861. The measurements were not standardized, but the meeting led to the founding of the German Anthropological Society and of the German Archiv für Anthropologie.

Other research
Baer also did some work in entomology and was instrumental in the establishment of the Russian Entomological Society, of which he was the first president in 1860. He was deeply interested in pisciculture and in the Russian fisheries. He wrote on the origin of the tin found in ancient bronze, on the routes of Odysseus' voyages and on the whereabouts of biblical Ophir.

The man – the Russian
Among his other abilities Baer had talents that distinguished him socially. He had great wit, which endeared him to those who knew him, and he was very loyal to his friends. One friend in particular may be singled out. In the winter of 1839-1840 Baer made the acquaintance of the Grand Duchess Helen Pavlovna, the former Princess Frederika Charlotte Marie of Württemberg. The wife of Grand Duke Michael Pavlovitch, youngest brother of Czar Alexander I, she was an enlightened and intelligent patron of the arts and the sciences; Baer instructed her two daughters in natural history and enjoyed her friendship for many years.

Baer was a patriotic Russian, as is clear from the zeal with which he carried out his duties for the academy and from his evident interest in Russian geography and ethnography. But he was also an expressed enthusiast of Prussia. His true political views remain obscure, for some were expressed cryptically and others, we are told by his biographer Stieda, were probably eliminated from his publications by the censors.

Baer received many honours during his lifetime. An Island in the Russian North was named for him; and in 1864 the Estonian Knights held a celebration for him on the golden jubilee of his doctorate. They also published his autobiography, which was especially prepared for that event. In 1872, Volume 5 of the Archiv für Anthropologie was dedicated to him. Baer was elected a member of the Royal Society of London and of the Paris Academy. He was awarded the Copley Medal by the Royal Society and also received a medal from the Paris Academy. Alexander von Humboldt (1769-1859) personally brought him the medal from Paris, much to Baer's delight. Baer once wrote of Humboldt that he was "versatile, yet always accurate as an observer, deep and far seeing as a thinker, exalted as a seer" (Reden, I, 296). He might well have been speaking of himself.

After celebrating his 50th anniversary as doctor of medicine, von Baer in 1867 moved to Dorpat, where he died on November 16, 1876.

Von Baer's research in embryology
In Würzburg Döllinger had suggested that Baer begin a study of chick development by improved methods, studying the blastoderm removed from the yolk. Bear, however, was unable to meet the expense of purchasing the eggs and paying an attendant to watch the incubators. Baer's more affluent friend Christian Heinrich Pander, whom he had met in Dorpat and Berlin, did this work instead. In 1817 Pander described the early development of the chicks in terms of what is now generally known as the primary germ layers - that is, ectoderm, mesoderm, and endoderm.

From 1819 to 1834 Baer devoted most of his time to embryology, extending Pander's concept of germ-layer formation to all vertebrates. Through painstaking and patient effort he investigated germ cell lineage of a variety of species, thus establishing embryology as a comparative science. He made many important technical discoveries. He also studied the development of fish, amphibians, reptilians, mammalians, discovered blastula - a very important stage of development, studied notochord, the development of foetal membranes and germ layers.

In 1826 Baer discovered the egg of the mammal – including human - in the ovary, bringing to completion a search begun at least as early as the seventeenth century. William Harvey had unsuccessfully attempted to find eggs of the deer in the uterus; others, after Harvey's time, had mistaken ovarian follicles for mammalian eggs. Baer first found the true egg in Burdach's housedog, a bitch sacrificed for the investigations.

1827 he published his epoch-making discovery in De Ovi Mammalium et Homiinis genesi ("On the Mammalian Egg and the Origin of Man"). In it he describes for the first time the mammalian ovum, thereby establishing that mammals, including human beings, develop from eggs. Baer concludes that that "every animal which springs from the coition of male and female is developed from an ovum, and none from a simple formative liquid". This was a unity doctrine whose importance cannot be overemphasized.

In this work Baer also made reference to the germ layer theory, suggested the similarity of the early stages of embryonic development in related species, and observed the first rudiment of the dorsal spine, later called the notochord. Baer is also considered to be one of the founders of modern morphology as a result of his work in comparative embryology.

Baer emphasized that embryos resemble each other more than adults do, and he strongly opposed the popular opinion previously expressed by Johann Friedrich Meckel that embryos of one species pass through stages comparable to adults of other species - that they resemble adults of other species. Instead, he emphasized that embryos of one species could resemble embryos, but not adults of another, and that the younger the embryo, the greater the resemblance. This was in line with his epigenetic idea - basic to embryology ever since - that development proceeds from simple to complex, from homogenous to heterogeneous. The old idea, long disputed, that embryonic parts might be preformed in the egg was no longer tenable after Baer's work.

He described the development of vertebrates from conception to hatching or birth. Baer observed the formation of the germ layers and described the way in which they formed various organs by tubulation, and he knew this to be more or less similar in all vertebrates.

As part of the heritage of German Naturphilosophie in which he had been trained, Baer had a great interest in symmetry. His embryological observations led him to believe that there are four fundamental animal types that differ from each other according to their symmetry: the peripheral or radial, the segmental, the massive, and the double symmetrical (vertebrate). These types were very similar to the four embranchements described at approximately the same time by Baron Georges Cuvier (1769-1832).

Though Caspar Friedrich Wolff (1733-1794) and others had previously observed the fold like germinal development of various vertebrate embryos, it remained for Baer in this classic work on developmental anatomy to confirm the germ layer theory and to extend the concept to mammalian embryology.

Von Baer and the theory of evolution
In his early days as an embryologist Baer had begun to consider possible relationships, in terms of kinship, between animals. In 1859, the year that Charles Darwin's Origin of Species appeared, Baer published a work on human skulls suggesting that stocks now distinct might have originated from one form; the ideas of the two men were formulated completely independently. Baer, however, was no strong adherent to the doctrine of transformation (the pre-Darwinian term for evolution). Although he believed that some very similar animals, such as goats and antelopes, might be related, he was vehemently against the concept expressed in the Origin of Species that all living creatures might have evolved from one or a few common ancestors.

His discovery that embryonic homologues such as the fin of a fish and the hand of a man begin as nearly identical structures was cited later by Darwin to support his theory of evolution.

In his philosophical writings - and all his embryological writings were philosophical to some degree - Baer saw nature as a whole, even though not in terms of modern evolutionary theory. He viewed the development of organisms and of the cosmos in the same light, and his all-encompassing view of the universe brought together what might otherwise have seemed diverging threads in his thought. Entwicklungsgeschichte was the key word in the title of his most important work, as well as in his thought. His great contribution rested on his ability to envisage the organism as a historical entity, as a being that undergoes observable changes its life. Baer held some belief in limited transformationism, the idea that one kind of animal species might during the course of history be transformed into another, but when Darwin's Origin of Species was published in 1859, Baer could not agree that all organisms could have evolved from a few progenitors.

As for his writing, Baer began more than he completed. The second volume of his great Entwicklungsgeschichte was never finished; he neglected even to read the proofs when the publisher decided to bring it out unfinished. He began, but failed to complete, other writings; he never completely described his collections from Novaya Zemlya. Nonetheless, he was a prolific lecturer and author. The second edition of Christian Hermann Ludwig Stieda's (1837-1918) biography enumerates approximately 300 of his publications, and the list is incomplete.


    In den Organismen sind die einzelnen Theile derselben nach dem Typus und Rhythmus des zugehörigen Leben-Processes und durch dessen Wirksamkeit gebaut, so dass sie einem andern Lebens-Processe nicht dienen können. Deswegen glaube ich die verschiedenen Lebens-Processe, mit musikalischen Gedanken oder Thematen sie vergleichend, Schöpfungsgedanken nennen zu können, die sich ihre Leiber selbst aufbauen. Was wir in der Musik Harmonie und Melodie nennen, ist hier Typus (Zusammensein der Theile) und Rhythmus (Aufeinanderfolge der Bildungen).
    Welche Auffassung der lebenden Natur ist die richtige?
    Und wie ist diese Auffassung auf die Entomologie anzuwenden?

    In his: "Reden, gehalten in wissenschaftlichen Versammlungen und kleinere Aufsätze vermischten Inhalts. Erster Theil: Reden."
    St.Petersburg: H. Schmitzdorff. Pp. 280-281.

    Es ist nothwendig, /../ dass man Typus und Rhythmus des Lebens nicht als Ergebniss des Stoffwechsels betrachte, sondern als dessen Leiter und Lenker, wie ein Gedanke oder Psalm wohl die Worte sucht und ordnet, um sich vernehmbar zu machen, nicht aber aus den einzelnen Wörtern nach deren eigenem Werth und Streben erzeugt wird.
    Welche Auffassung der lebenden Natur ist die richtige?
    Und wie ist diese Auffassung auf die Entomologie anzuwenden?

    In his: "Reden, gehalten in wissenschaftlichen Versammlungen und kleinere Aufsätze vermischten Inhalts. Erster Theil: Reden." St.Petersburg: H. Schmitzdorff. Pp. 282-283.

    Ohne Zweifel ist auch der Organismus ein mechanischer Apparat, eine Maschine, die sich selbst aufbaut. Der Lebensprocess verläuft unter ununterbrochenen chemischen Vorgängen; deswegen könnte man einen Organismus auch ein chemisches Laboratorium nennen; allein er ist zugleich auch der Laborant, indem er die für den Fortgang der chemischen Operationen notwendigen Stoffe aus der Aussenwelt aufnimmt; kann er sie nicht haben, so hört der Lebensprocess auf.
    Ueber Zielstrebigkeit in den organischen Körpern insbesondere.
    In his: "Reden, gehalten in wissenschaftlichen Versammlungen und kleinere Aufsätze vermischten Inhalts. 2ter Theil: Studien aus dem Gebiete der Naturwissenschaften. "
    2te Ausgabe. Braunschweig: Verlag von F. Vieweg. Page 188.

This article is also available in Estonian translation.


Works by Karl Ernst von Baer:
  • De morbis inter esthonos endemicis
    (On the diseases endemic among the Estonians).
    Doctoral thesis, Dorpati, 1814.
  • Ueber Entwicklungsgeschichte der Thiere: Beobachtung und Reflexion.
    Königsberg, Bornträger, 1828-1888. 2 volumes i 3. Volume 1, 271 pages, 1828.
    In response to demands by subscriber to the treatise, the publishers issued volume 2, 315 pages, in incomplete form in 1837. Last part of volume II, sometimes called volume 3, was added by Ludwig Stieda in 1888.
  • Vorlesungen über Anthropologie für den Selbstunterricht.
    Königsberg, 1824.
  • De ovi mammalium et hominis genesi. Epistola ad Academiam Imperialem Scientiarum Petropolitanam.
    Lipsiae, L. Vossius, 1827.
    German translation, edited by B. Ottow:
  • Ueber die Bildung des Eies der Säugetiere und des Menschen. Leipzig, 1927.
    English translation by C. D. O'Malley:
  • On the Genesis of the Ovum of Mammals and of Man; a letter to the Imperial Academy of Sciences of St. Petersburg. Isis, June 1956, 47: 117-153.
  • Beiträge zur Kenntniss der niedern Thiere. Mit 6 Kupfertaf.
    Nova Acta Leopoldina, 1827, XIII, N 2, S. 525-762.
    Fragments in English - Scientifical Memoirs, Nat History, 1855, 1.
  • Expédition à Novaia Zemlia et en Laponie. Thierisches Leben.
    Bull. sci., 1838, 3, S. 343-352; Ann. Berghaus, 1838, 3, VI, S. 20-28.
    English translation in Edinburgh New Philosophical Journal, 1840, 28, p. 93-103.
  • On the recent Russian Expeditions to Novaia Zemlia.
    Journal of the Geographical Society of London, 1838, 8, p. 411-415.
  • On the ground ice or frozen soil of Siberia.
    Journal of the Geographical Society of London, 1838, 8, p. 210-213.
    Athenaeum, 1838, N 540, p. 169.
    The American Journal of Sciences and Arts by B. Silliman (New Haven), 1839, 36, p. 210-212.
  • Recent intelligence of the frozen ground in Siberia.
    Journal of the Geographical Society of London, 1838, 8, p. 401-406.
    Athenaeum, 1838, N 565, p. 509.
  • Ueber das Klima von Sitcha und den Russischen Besitzungen an der Nordwestküste von Amerika überhaupt, nebst einer Untersuchung der Frage, welche Gegenstände des Landbaues in diesen Gegenden gedeihen können.
    Bull. sci., 1839, 5, S. 129-141, 146-152.
    Fragment in English in: Athenaeum 1839.
  • Sur la fréquence des orages dans les régions arctiques.
    Bull. sci., 1840, 6, pp. 66-73.
    English translation in Edinburgh New Philosophical Journal, 1840, 29, p. 90-93.
  • Ueber die Bildung des Eies der Säugetiere und des menschen.
  • Crania selecta etc. Petropol, 1859.
  • Ueber Papuas und Alfuren.
  • Beiträge zur Kenntniss des russischen Reiches.
  • Caspische Studien (I-VI).
  • Reden, gehalten in wissenschaftlichen Versammlungen und kleinere Aufsätze vermischten Inhalts.
    3 volumes, Sankt Petersburg, 1864-1876.
    Volume 1, 1864, vi+296 pages, includes:
  • Das allgemeine Gesetz der Natur in aller Entwickelung.
    Pages 35-74.
  • Welche Auffassung der lebenden Natur ist die richtige? und wie ist diese Auffassung auf die Entomologie anzuwenden?
    Pages 237-284.
    Volume 2, 1876, xxv + 480 pages, includes:
  • Ueber den einfluss der äusseren Natur auf die socialen Verhältnisse der einzelnen Völker und die Geschichte der Menschen überhaupt. Pages 3-47.
  • Ueber den Zweck in den Vorgängen der Natur. Erste Hälfe. Ueber Zweckmässigkeit oder Zielstrebigkeit überhaupt.
    Pages 47-105.
  • Ueber Zielstrebigkeit in den organischen Körpern insbesondere. Pages 171-234.
  • Ueber Darwin's Lehre. Pages 235-480.
    Volume 3, 1873, xi + 385 pages.
    These three volumes, published at the end of von Baer's career, included lectures, studies from the realm of the natural sciences, and historical questions answered with the help of the natural sciences. Thomas Huxley greeted the partial publication of some of von Baer's earlier essays in English with the comment that von Baer's works demonstrated "the deepest and soundest philosophy of zoology, and indeed of biology generally, which has yet been given to the world."
  • Nachrichten über Leben und Schriften des Geheimrathes Dr. Karl Ernst von Baer, mitgetheilt von ihm selbst. Veröffentlicht bei Gelegenheit seines fünfzigjährigen Doctor-Jubiläums, am 29. August 1864, von der Ritterschaft Esthlands.
    St. Petersburg, printshop of the imperial academy of sciences, 1865. Privately distributed in 400 copies. Trade editions appeared under same title, St. Petersburg 1866.
  • A letter to Ch. Darwin of 5 May 1873. Dorpat (Tartu).
    The Darwin Papers, Manuscripts Room, Cambridge University Library, Cambridge, England, 160.
  • Nachrichten über Leben und Schriften.
    Autobiography. Canton (USA). Science History Publications. 1986, XIV+389 pages. Edited and with a preface by Prof Jane Oppenheimer. Translated by H. Schneider.
  • Peter des Grossen Verdienste um die Erweiterung der geographischen Kenntnisse.
    Treatise, Petersburg, 1872.
  • Homerische Localitäten in der Odys. Braunschweig, 1879.
  • Lebensgeschichte Cuviers.
    Republished by L. Stieda in Braunschewig, 1897. Other works:
  • F. von Wrangell:
    Russian America. Statistical and ethnographical information. /With additional material by Karl Ernst von Baer.
    Translated from the Beiträge zur Kenntniss des Russischen Reiches und angränzenden Länder Asiens, 1839: 1: - Materials for the Study of Alaska History, 15. Wd. by R. A. Pierce. Kingston - Ontario: Limestone Press, 1980. XXII+204 p.
  • Fragments relating to Philosophical Zoology.
    Selected from the Works of K. E. von Baer. Scientific memoirs, natural history. Ed. by A. Henfrey and T.H. Huxley. London, 1853, 7, p. 176-238.
  • Karl Ernst Von Baer {1792-1876} Anton Dohrn {1840-1909} : Correspondence.
    Transactions of the American Philosophical Society, Vol 83, Part 3, 1993) by Christiane Groeben (Editor) Works on Karl Ernst von Baer:
  • L. Stieda
    Karl Ernst von Baer.
    2nd ed. (1886). With extensive bibliography.
  • B.E. Raikov
    Karl Ernst von Baer. 1968. With extensive bibliography.
  • Jane Oppenheimer:
    Baer, Karl Ernst von, in Dictionary of Scientific Biography, vol. 1, 1970, Earlier works on embryology etc.
  • Regner de Graaf (1641-1673):
    De mulierum organis generationi inservientibus tractatus novus... Lugduni Batavorum, ex. off. Hackiana, 1672.
    De Graaf demonstrated ovulation anatomically, pathologically and experimentally. In this work he included the first account of the Graafian follicle.
  • Johann Friedrich Cassebohm, 1699?-1743:
    Tractatus quatuor anatomici de aure humana. Tractatus quintus anatomicus de aure humana. Cui accedit tractatus sextus de aure monstri humani.
    Halae Magdeburgi, sumtibus Orphanotrophei, 1734-1735.
    Cassebohm's studies of the embryonic ear far surpassed his predecessors, including Valsalva and Morgagni, and were not themselves surpassed until the work of Emil Huschke (1797-1858) and von Baer. See No. 1547.
  • Heinrich Christian Pander, Ignaz Döllinger, d'Alton (professor in Bonn):
    Beiträge zur Entwicklungsgeschichte des Hühnchens im Ei.
    Würzburg, 1817.
  • Caspar Friedrich Wolff, 1733-1794:
    Theoria generationis.
    Halae ad Salam, litt. Hendelianis, 1759.
    Wolff observed in great detail the early processes of embryonic differentiation. He disposed of the "preformation" theory, substituting his view that the organs are formed from leaf-like (blastodermic) layer. He thus laid the foundation of the "germ-layer" theory of Baer and Pander. His book includes descriptions of the "Wolffian bodies" and "Wolffian ducts". Reprinted 1966.
  • Charles Bonnet, 1720-1793:
    Considérations sur les corps organisés.
    2 volumes. Amsterdam, M. M. Rey, 1762.
    Bonnet's theory of generation offered the best synthesis of 18tch century ideas of development and remained a leading authority until von Baer. Bonnet believed in the preformation of the embryo. He used many of Albrecht von Haller's (1708-1777) arguments to support his own opinions. J. Needham
  • Heinrich Christian Pander, 1794-1865:
    Dissertatio sistens historiam metamorphoseos, quam ovum incubatum prioribus quinque diebus subit.
    Wirceburgi, T. E. Nitribitt, 1817.
    Pander's doctoral thesis in which he announced his discovery of the trilaminar structure of the chick blastoderm, which term he also coined. This discovery stimulated von Baer's research. Pander later paid for the publication of an illustrated German-language edition of the thesis. The original Latin edition has no illustrations.

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