(c) & Disclaimer: Note that this is a biased choice of dates relevant to biology, obtained by compiling many different sources, often using the original texts and not the WWW only; note that care has been taken to check information and rewrite it when needed, however it is likely that they still contain many errors; the links are chosen to be as diverse as possible, they do not engage the responsability of the author; please send comments and corrections here)

1875-1899

1920-1939

Causeries

1900 Paul Uhlenhuth (1870-1957), successor of Behring in Marburg, discovers the "precipitin" reaction: if we inject in an animal serum of another animal, after some days, the serum of the former will precipitate the serum of the latter in vitro. This reaction is highly specific and reproducible.

1900 Hugo De Vries, Karl Correns (München, 1864 - Berlin, 1933) and Erich von Tschermak -Seysenegg (1871-1962) claim to have independently discovered and verified Gregor Mendel's principles, marking the beginning of modern genetics.

1900 Kurt Herbst (1866-1946) at the Stazione Zoologica in Napoli uses calcium-free sea water to separate blastomeres of the sea urchin.

1900 Walter Stanborough Sutton (1877 - 1916) observes homologous pairs of chromosomes in grasshopper cells, showing that during meiosis the chromosome pairs split, and each chromosome goes to its own cell.

1900 Charles William Andrews (?-?) discovers several early higher primate remains in the Fayum Depression region in Egypt. Aegyptopithecus is he best known of the propliopithecids from the Fayum, about the size of a cat. Aegyptopithecus is often placed at the base of the Catarrhine radiation.

1900 Karl Landsteiner (Wien, 1868 - New York, 1943), using the precipitin reaction, discovers that man has different types of blood, that he names the A, B and O blood groups.

1900 Free radicals (triphenylmethyl) are prepared by Moses Gomberg (Elizabetgrad, Russia 1866 - Ann Arbor 1947), opening a new era in chemistry, that was later to be very important for biology.

1900 Max Planck (Kiel, 1858 - Göttingen, 1947) develops the theory of quanta. Although mainly important to basic physics, it has also much implication in biology (in particular in photosynthesis).

1900 Jacques Loeb, graduated as a MD from the University of Strasbourg, induces artificial parthenogenesis in sea urchin eggs by stimulating them with a weak organic acid and resuspending them in concentrated sea water.

1900-1901 The Yellow Fever Commission, led by the US army surgeon Walter Reed (1851-1902), investigates the transmission of yellow fever in La Havana, Cuba.

1901 Jokichi Takamine (1854-1922) discovers and names epinephrine (later adrenaline), the main surrenal hormone.

1901 William Einthoven (1860-1927), professor of physiology at the University of Leiden and former coworker of the physicist Gabriel Lippmann, constructs the string galvanometer. This enables him to improve the invention of Waller, thus being the recognized creator of electrocardiography. Einthoven's apparatus weighted no less than 300 kg and required five persons to operate.

1901 Emil Fischer determines the structural formula of valine.

1901 The Rockefeller Institute is created on the model of the Institut Pasteur in New York.

1901 Hermann Henking (1858-1942) and colleagues report an "accessory chromosome" present in spermatozoa, later identified as the sex chromosome.

1901 Thomas Harrison Montgomery Jr. (?-?) notices the homologous pairing of maternal and paternal chromosomes at synapsis prior to the reductive division.

1901 Franz Hofmeister (1850-1922) building on the work of Liebig, Claude Bernard and discussions by Berthelot and many others proposes that life results from enzyme activity: for every vital reaction there is a specific enzyme responsible.

1901 A. P. Pavlov (?-?) publishes Le Crétacé inférieur de la Russie et sa faune in Moscow.

1901 Hans Spemann (Stuttgart 1869 - 1941) Uber Correlationen in der Entwicklung des Auges performed constriction experiments on newt eggs, defining the first steps of animal ontogeny.

1901-1903 In his publication Mutationslehre De Vries's substantiates his thesis that species are not continuously connected but arise through sudden large changes.

1901-1904 Following Landsteiner, George Frederick Nuttall investigates the serological relationships of animals using the precipitin reaction.

1902 James Mark Baldwin (1861-1934) elaborates the concept of organic selection, summarized in papers brought together in Development and Evolution and further discussed in Darwin and the Humanities, introducing a mechanism into evolution theory whereby the effects of acquired adaptations can be taken into account without violating principles of natural selection. He is well known for having influenced important thinkers as diverse as Piaget, Vygotsky, and Mead.

1902 William Bateson coins the word "genetics".

1902 Landsteiner discovers that A and B blood group individuals can yield the AB blood group in their progeny.

1902 Clarence Erwin McClung (Philadelphia 1870 - 1946) proposes that certain chromosomes whose synaptic mates are different in appearance or entirely absent, such as Hermann Henking's accessory chromosomes (X), are responsible for sex determination.

1902 E. Perrier (?-?) and C. Gravier (?-?) write La tachygenèse ou accélération embryogénétique, where they elaborate on the variation in comparative development in diverse organisms.

1902 The term "hormone" is resurrected (not 1906, as the Oxford English Dictionary states) by the English physiologists William Maddock Bayliss (Wolverhampton 1860–1924) and Ernest Henry Starling (London,1866 - 1927, on a ship near Kingston Harbour, Jamaica) when they discover "secretin", a hormone produced by the intestinal mucosa which acts on the pancreas.

1902 Peter Kropotkin (Moscow 1842 - Dmitrov 1921), very well known for his anarchist's views and theories publishes Mutual Aid a factor of Evolution, an important landmark in the future trend of population studies (leading to the widely spread anthropomporphic concept of "altruism").

1902 Otto Loewi (Frankfurt-am-Main, 1873 - 1961) discovers that animals must build proteins from amino acids as building blocks (Über Eiweisssynthese im Tierkörper).

1902 Emil Fischer and Franz Hofmeister demonstrate that proteins are polypeptides.

1902 Sutton, observing chromosomal movements during meiosis, announces his discovery of chromosome segregation in his paper "On the Morphology of the Chromosome Group in Brachyotola." Sutton states that chromosomes are paired and may be the carriers of heredity. He suggests that Mendel's "factors" must be located on chromosomes.

1902 Archibald Garrod (?-?), through his study of alkaptonuria observes the association of large quantities of "alkapton" (homogentisic acid) and heredity, and proposes that inherited diseases reflect a patient's inability to make a particular enzyme, which he refers to as "inborn errors of metabolism" (this is the title of his book, published in 1908). This makes the connection between Mendelian heredity and the biochemical pathways of reproduction in the individual organism. This starts the line of research on genes and enzymes that became indispensable to the growth of human genetics. This was a first recognition of a role for genetics in biochemistry, but the idea remained mostly unappreciated (however, see in 1909 Cuénot) until the work of Boris Ephrussi in the late thirties and Beadle and Tatum in the 1940's.

1902 Boveri pursuing his studies of sea urchin eggs fertilisation and development states that a particular combination of the chromosomes, rather than their sheer number, is essential for a normal development of the cell.

1902 William Bateson coins the terms F1, F2, allelomorphism, homozygote, and heterozygote. He also lists some 26 different cases of established allelomorphism in wheat, maize, peas, snapdragon, Datura, Oenothera, mouse, cattle, fowl, and man.

1902 Charles Robert Richet (Paris 1850 - Paris 1935) working with Paul Portier (Bar-sur-Seine, 1866 — Bourg-la-Reine, 1962) investigates the phenomenon of hyper-reaction to foreign substances and gives its the name of anaphylaxis.

1902-1903 Walter Sutton and Theodor Boveri point out the parallelism between chromosome behavior and Mendelism, Sutton and Boveri, working independently, propose that each egg or sperm cell contains only one of each chromosome pair. This connects two phemonema: the patterns by which pairs of Mendel's factors assort themselves and the precisely similar sorting and recombination of the chromosomes in the formation of the germ cells and the fertilization of theegg. Sutton notices that chromosomes occur as pairs, and that gametes (egg and sperm cells) receive only one chromosome from each pair when they form during meiosis. This corroborates Mendel's theory that the genetic "factors" are segregated. Sutton gives Mendel's "factors" the name we use today: "genes."

1903 Bertrand Arthur William Russell (Trelleck, 1872 - 1970) publishes The Principles of Mathematics a first version of what was to become one of the major work of logics and analytical philosophy.

1903 Creation of the Lister Institute in Cambridge on the model of the Institut Pasteur in Paris. Joseph Lister had strongly supported the approach of Pasteur in his vaccination againts rabies, but the public opinion in England was extremely active against what was perceived as cruelty against animals in France, in the fight against rabies. For the last part of the century English people bitten by dogs had to be treated in France, and this triggered, after much debate, the creation of an Institute against infectious diseases. Initially proposed to be named the "Jenner-Pasteur Institute for the Prevention of Infectious Diseases", it was subsequently named "British Institute of Preventive Medicine", and finally the Lister Institute.

1903 The concepts of phenotype and genotype are defined by Wilhelm Ludvig Johannsen Copenhagen 1857 - Copenhagen 1927) to summarize the discussion of Weissman and contemporaries about the transmission and expression of heredity.

1903 Wilhelm Roux shows that the point of entrance of the sperm marks the future mid-ventral line of the frog.

1903 Charles Jules Henri Nicolle (Rouen, France, 1866 - Paris, 1936) arrives at the newly created Institut Pasteur at Tunis (Tunisia), and entirely renovates it, much expanding its capacity. Starting with the study of local diseases he will develop and extend the identification of microbes and parasites, and in particular the role of insect vectors. He is the first to use primates (chimpanzees and monkeys) as models to human diseases.

1903 Carl Neuberg (?-?) first uses the term "Biochemie" for chemical biology.

1904 Auguste Prenant (?-?) publishes his Traité d'histologie, a reference for cell biology during several decades in France.

1904 Ross Granville Harrison (Germantown, USA, 1870 - New Haven 1959) studies nerve development in the embryo and obtains experimental induction of the lens by transplanting the optic cup.

1904 Stoltz (?-?) determines the chemical formula for epinephrine and achieves a total chemical synthesis of the substance.

1904 Alfred Giard (1846-1908), head of the Laboratoire de Biologie Marine in Wimereux, near Boulogne, publishes his Controverses transformistes, which had to have a deleterious impact in France by imposing, from the Ecole Normale Supérieure (where Pasteur had been a student and the Director) and the Sorbonne, inadequate Lamarckian principles for more than half a century, retarding siginficantly the contribution of France in Genetics.

1904 William Bateson demonstrates that some characteristics of the phenotype are not independently inherited. This introduces the concept now called 'gene linkage' and led to the need for 'genetic maps' that describe the order of the linked genes.

1904-1905 Arthur Harden (Manchester, UK, 1865 - Bourne End, 1940) and William John Young (1878 - 1942) working on the fermentation of sugars, isolate the first organic coenzyme: cozymase. They demonstrate that fermentation require the simultaneous presence of both a "colloidal" heat labile fraction and a diffusible, low molecular weight, heat stable molecule, later found to be NAD. They also demonstrate the necessity of phosphate in alcoholic fermentation by zymase.

1904 William Bateson demonstrates that some characteristics are not independently inherited. This introduces the concept now called 'gene linkage' and led to the need for the construction of 'genetic maps' that describe the order of the linked genes.

1905 Johannsen favors De Vries view that heredity is governed by particulate elements and abbreviates "pangenes" into "genes" in Arvelighedslaerens elementer ('The Elements of Heredity').

1905 Edmund Beecher Wilson (1856-1939) and Nettie Maria Stevens (Westford,USA, 1861-1912) studying insects, independently propose that separate X and Y chromosomes determine sex. Stevens, studying the carab Tenebrio molitor shows that a single Y chromosome determines maleness, and two copies of the X chromosome determine femaleness.

1905 George Nuttall who had found bactericidal properties of blood, demonstrates the importance of intestinal bacteria in digestion.

1905 Franz Knoop (1875-1946) describes the beta-oxidation of fatty acids after tagging fatty acids with a benzene ring.

1905 Frederick Frost Blackman (1866 - 1947) publishes Optima and Limiting Factors, in which he applies physico-chemical ideas to biological problems. He points out that photosynthesis involves several processes, its rate being determined by several possible limiting factors.

1905 John Scott Haldane (Edinburgh, UK, 1860 - 1936) and John Gillies Priestly (?-?) investigate the role of carbon dioxide in the regulation of breathing and state: "The experiments…indicate clearly that under normal conditions the regulation of the lung-ventilation depends on the pressure of CO2 in the alveolar air. Even a very slight rise or fall in the alveolar CO2 pressure causes a great increase or diminution in the lung-ventilation…. For each individual the normal alveolar CO2 pressure appears to be an extraordinarily sharply defined physiological constant."

1905 Lucien Claude Jules Cuénot (Paris, France 1866 - Nancy, 1951) extends Mendel's discoveries to animals and discovers the first lethal allele: the yellow coat color allele in mice (agouti). This is, independently of Garrod, another indication of the link between genes and metabolic activities.

1905 Richard Adolf Zsigmondy (Wien, Austria 1865 - Göttingen, 1929) applies the centrifuge to the study the heterogeneous nature of colloids, making a more detailed understanding of protoplasmic constituents possible.

1905 William Bateson and Reginald Crundall Punnett (1875–1967) investigatethe exceptions to Mendel's rules, leading to the discovery of genetic linkage and gene interaction. Punnett publishes the first textbook in genetics Mendelism.

1906 Clemens von Pirquet (Hirschstetten, 1874 - München, 1929) describes the phenomenon of Allergie (excessive and altered reactivity).

1906 Henri Poincaré publishes La Science et l'Hypothèse, one of the most insightful book on hypothesis-driven scientific discovery.

1906 Craig W. Woodworth (?-?) and William Ernest Castle (1867 - 1962) introduce Drosophila melanogaster as a new experimental material for genetic studies.

1906 Christiaan Eijkman (Nijkerk, 1858 - 1930) discovers that the anti-beriberi agent is a water-soluble component of rice polishings.

1906 Herbert Spencer Jennings (1868-1947) publishes The Behavior of the Lower Organisms after having developed studies on the orientation behavior of the Protozoa.

1906 Fredrick Gowland Hopkins (1861 - 1947) explains dietary deficiency by a biochemical investigation of the lack of essential amino acids in the diet.

1906 Jules Bordet and Octave Gengou (1875 – 1957) discover the bacillus responsible for whooping cough (Bordetella pertussis) at the Institut Pasteur du Brabant (Bruxelles).

1906 Sunao Tawara (1873-1952) working on the excitation conduction system of the mammalian heart, discovers the atrio-ventricular node of the heart.

1906 Yves Delage (1854-1920) a pupil of Loeb, finds new ways to trigger the development of the sea urchin's egg.

1906 Mikhail Semenovitch Tswett (Tsvett) (1872-1919) creates the technique of chromatography. He uses the technique to separate plant pigments: hence, its name.

1906-1916 The Yellow Fever Commission, now led by William Crawford Gorgas (1854-1920) eliminates malaria and yellow fever in the Panama Canal Zone by eradicating the Aedes and Anopheles mosquitoes.

1906-1926 Richard Willstätter (Karlsruhe, 1872 - Locarno, 1942) and his colleagues in a long series of works, describe the chemical structure of the chlorophyll pigments.

1907 William James publishes his influential Textbook of Psychology.

1907 Arthur Keith (1866 - 1955) and Martin William Flack (?-?) discover the auriculo-ventricular bundle of the human heart (sino-atrial node of the heart) and recognize is role as the heart's pacemaker.

1907 Walter Morley Fletcher (1873 - 1933) and Fredrick Hopkins show that lactic acid is formed quantitatively from glucose during anaerobic muscle contraction. Hopkins also shows that part of the lactic acid is oxidized to furnish energy for the synthesis of glycogen from the remaining lactic acid. That same year Fletcher also observes a correlation between eating polished rice and beriberi.

1907 Richard Norris Wolfenden (Bolton, 1854 -1926) a disciple and friend of Morell Mackenzie, (1837-1892), having founded together with him the Journal of Laryngology and Rhinology became so disappointed that his friend Mackenzie unfairly had been publically viciously attacked over his role in the medical diagnosis and treatment of the German Crown Prince Wilhelm, that he left medicine, starting a career of marine biologist ending in 1907 after cruises in the Atlantic, including the Azores, Madeira and Gibraltar in 1904-1906 and between the Faeroe Banks and Norway. Having acquired a sailing 20 m yacht , the "Walwin", he started dredging around the Orkneys, where he began X-ray studies on marine invertebrates, mainly echinoderms and large crustaceans. He began monthly cruises during summer months in the Faeroe-Shetland Channel in 1899 until 1905, from 1902 with a new yacht, the 30 m "Silver Belle". He sent much of the material from the cruises to different specialists and began publishing on radiolarians and copepods, settling later on the second group and during the 1900s he spent much time at the Plymouth Laboratory and the British Museum of Natural History while also visiting the Stazione Zoologica in Napoli a few times.

1907 H. V. Wilson (1863-?) dissociates sponges into individual cells and cell clusters and allows them to fuse, demonstrating the high level of cell individuality in phenomena of coalescence and regeneration in sponges.

1907 Ross Harrison maintains frog neural crest tissues in culture and develops new techniques for culturing and studying isolated cell or tissue fragments apart from the intact whole organism.

1907 Frank Lutz (?-?) proves that the mutation "gigas" in the evening primrose Oenothera lamarckiana contains an extra set of the usual chromosomes This leads to the analysis and artificial production of polyploidy in plants, a much used technique for crop improvement.

1907 Bertram Borden Boltwood (1870-1927) studying the concept of "radioactive series" finds that lead is always present in uranium and thorium ores. Believing that lead must be the final product of the radioactive decay of uranium and thorium, he proposes that since one knows the rate at which uranium decays (its half-life), one can use the proportion of lead in the uranium ores as a clock. to determine the age of minerals.

1907 Boveri demonstrate that the chromosomes have qualitatively different effects on development by removing individual chromosomes from developing sea urchin eggs. Only those cells that contained a full complement ofchromosomes developed normally.

1907 Otto Schoetensack (1850-1912) discovers the mandible of a primitive hominid in a sandpit in Mauer, Germany. This specimen has been referred to as "Heidelberg Man" and is a less archaic form of Homo erectus than Java Man.

1907-1917 Charles Rupert Stockard (?-?) studies the effects of chemicals on embryologic development and produced cyclopia and other monstrosities by the use of lithium and other agents and defines "critical moments" in the embryo development.

1908 H. Nilsson-Ehle (?-?) makes an analysis of the quantitative inheritance in the color of wheat kernels.and provides a useful model for the further analysis of continuously variable characters.

1908 Creation of the Institut Pasteur at Brazzaville (Congo, then Afrique Equatoriale Française), working in priority on trypanosomiasis (maladie du sommeil).

1908 Albert Léon Charles Calmette (Nice, France, 1863 - Paris 1933) and Camille Guérin (Poitiers, France, 1872 - 1961) begin to develop a vaccine against tuberculosis by attenuating it by repeated cultivation on plates. This vaccine, called BCG after the name of the strain (Bacille de Calmette et Guérin), is not used until 1921.

1908 Alexis Carrel (Lyon, France, 1873 - Paris, 1944) performs the first transfusion of blood for hemorrhagic disease of the newborn in New York City.

1908 Godfrey Harold Hardy (Cranleigh, UK, 1877 - Cambridge, 1947) a Cambridge mathematician, and Wilhelm Weinberg (1862–1937),) a Stuttgart physician, independently formulate the theorem that in the absence of mutation and selection, the frequency of a gene in any large, randomly mating population will reach an equilibrium in one generation and remain in equilibrium thereafter regardless of whether the gene is dominant or recessive. Also, the genotypic frequencies of a population in equilibrium with two alleles with frequencies p and q are given by the formula p2 + 2pq + q2. This theorem forms the mathematical basis for population genetics.

1908 Charles Nicolle and L. Manceaux (?-?) describe the presence of a parasite, Toxoplasma gondii, in a rodent in Tunisia. This parasite, which is innocuous for the adult, is very dangerous for the foetus, in whom it degrades the muscle and nervous systems.

1909 H. Ubrecht (1853 - 1915) publishes Die Säugetierontogenese on the evolution of Mammalia.

1909 Phoebus Aaron Theodor Levene (1869-1940), assuming that proteins are the support of heredity, studies nucleic acids to understand their role and discovers that the sugar ribose is found in some nucleic acids, those we now call RNA. He subsequently analyszes the compositon of nucleic acids and proposes that they are made of tetranucleotides in constant proportion, making them a monotonous macromolecule. This played an important role in delaying the discovery of DNA as the material supporting heredity.

1909 Howard Rickett (-) describes the now well-known Rickettsia in, A Micro-Organism Which Apparently Has a Specific Relationship to Rocky Mountain Spotted Fever.

1909 William Bateson first applies Mendel's laws to animals.

1909 Johannsen demonstrates that natural selection cannot act on genetically pure lines but can only isolate existing genotypes. Therefore, natural selection can only influence evolutionary change if there is a source of genetic variability. He coined the terms 'gene' to describe the carrier of heredity; 'genotype' to describe the genetic constitution of an organism; and 'phenotype' to describe the actual organism,which results from a combination of the genotype and the various environmental factors.

1909 Henry Fraser (?-?) and AT Stanton (?-?) after Eijkman and Fletcher, observe in a Javanese expedition that in selected groups under close observation beriberi occurs in persons who are eating a polished-rice diet, while those eating raw rice do not contract the disease.

1909 William Castle and John Charles Phillips (?-?) transplant an ovary from a black guinea pig into a white one and show that it would still produce black offspring if mated to a black male. This is intended to show that the hereditary characteristics of germ cells is unaffected by somatic influences.

1909 Frans Alfons Ignace Maria Janssens (St.-Niklaas, Belgium, 1863 - Wichelen, 1924) suggests that the chiasmata observed between synaptic chromosomes are evidence for the phenomenon of "chiasmatypie" (named today "crossing-over") among linked genes.

1909 Rollins Adams Emerson (1873-1947) discovers multiple allelomorphism in maize and also in beans.

1909 Svante Gustaf Arrhenius (Vik, Sweden, 1859- Stockholm, 1927) and Søren Peter Lauritz Sørensen (1868 - 1939) show that the hydrogen ion concentration in a solution could be experimentally determined. Sørensen pointed out the effect of pH on enzyme activity.

1909 Charles Nicolle, director of the Institut Pasteur at Tunis, demonstrates that the typhus fever is transmitted by the body louse.

1909 Jean Eugène Bataillon (Annoire, France 1864 — Castelnau-le-Lez 1953) discovers that it is possible to trigger the frog's egg development by pricking it with a needle dipped in serum (the phenomenon of pseudogamy).

1910 In a long series of pioneering experiments, Morgan proposes a theory of sex-linked inheritance for the first mutation discovered in Drosophila melanogaster: white eye. Morgan, who until then was a strong opponent of the theory of Wilson and Stevens on the determination of sex, acknowledges that his studies of Drosophila's characters support their hypothesis.

1910 James Bryan Herrick (1861–1954) discovers sickle cell anemia in a Black American: "The red corpuscles varied much in size, many microcytes being seen and some macrocytes…. The shape of the reds was very irregular, but what especially attracted attention was the large number of thin, sickle-shaped and crescent-shaped forms."

1910 Peter Boysen-Jensen (Hjerting, Denmark, 1883 — Frederiksberg, 1959) establishes the existence of phytohormones or auxins which are responsible for the chemical transmission of growth responses of higher plants. He demonstrates that the phototropic influence is material, since it can cross an incision, but cannot pass through an agar-agar or a mica barrier.

1910 Ivan Petrovitch Pavlov (Riazan, 1849 - Leningrad, 1936) using dogs with a minimum of invasive surgery, discovers classical conditioning.

1910 John Murray, who had been on the Challenger expedition, and Norwegian Johan Hjort (?-?) lead the Michael Sars deep-sea expedition, making the word "oceanography" current.

1910 Oskar Heinroth (1871–1945), working on duck taxonomy, discovers imprinting behavior.

1911 Henry Hallett Dale (London, 1875 - 1968) working on ergot extracts discoversthe properties of histamine.

1910 Paul Ehrlich discovers that solutions of salversan selectively kill the organism responsible for syphilis.

1910 Epstein (?-?) and Reuben Ottenberg (?-?) show that the human blood groups (A, B, O) are inherited in accord with Mendelian principles.

1910-1911 Schlosser (?-?) excavates Oligocene primate remains from the Fayum in Egypt.

1910-1920 Morgan proves that genes are carried on chromosomes, establishing the basis of modern genetics. This was followed by the announcement of the gene theory, including the principle of linkage. With his co-workers, he pinpointed the location of various fruit fly geneson chromosomes, establishing the use of Drosophila fruit flies to study heredity. Morgan's group also demonstrated the existence of sex-linked genes, and over the next ten years expandedthe idea to other trait linkages, using "crossing-over" to help determine the location of genes.Morgan explained the separation of certain inherited characteristics that are usually linked as caused by the breaking of chromosomes sometimes during the process of celldivision. Morgan begins to map the positions of genes on chromosomes of the fruit fly.

1910 Charles Scott Sherrigton (London, 1857 - Eastbourne, 1952) describes the nociceptive reflex after noxious treatments.

1911 Casimir (Kazimierz) Funk (1884-1967) demonstrates that beriberi can be cured in pigeons by feeding them a concentrate made from rice polishings. From those he isolates crystalline "antineuritis vitamine" (actually a vitamin B-complex) and coins the word "vitamine".

1911 Ethel Browne Harvey (Baltimore, 1885 - Falmouth, 1965) studies cortical changes in the sea urchin's egg during fertilization.

1911 The Institut Pasteur at Chengdu (Sichuan, China) is created. Its activity is devoted to the preparation of antivariola vaccine and vaccination against small pox. Due to insecurity the Institute has to close one month after its opening, and resumes its activity one year later. Ultimately the Institute will be able to produce 400 000 vaccine doses per year.

1911 Hubert Dana Goodale (1879 - 1968) introduces vital staining of the amphibian embryo as a method of tracing the fate of embryonic parts.

1911 Arthur Keith (Aberdeen, Scotland, 1866 - Downe, 1955) publishes his book in anthropology, Ancient Types of Man, where he states that moderns humans are as old as extinct forms of humans

1911 Charles Manning Child (1869 - 1954) formulates his axial gradient theory of regeneration and development in animals.

1911 Richard Semon (1859-1919) proposes a theory entirely based on the heredity of acquired characters in his book Das Problem der Vererbung erworbener Eigenschaften. He proposes that the power of the living substance to react (Reizbarkeit) makes it able to acquire a trace (Engramm) which will be passed in the future generations. This somatic induction of the germplasm is called mneme. Recent ressurections of this line of thought, usually hiding their Lamarckian flavour under some aspect of Darwinism, are fashionable, using a similar type of vocabulary.

1911 Richard Benedikt Goldschmidt (Germany, 1878 - USA, 1958) published the first edition of his Einfürung in die Vererbungslehre (Introduction to the Science of Heredity) in which he summarized his theory of sex determination as a matter of the rate of developmental expression for sex-determining genes. This was based on his study of intersexual forms in moths.

1911 Cuénot publishes his Genèse des espèces animales where he introduces the concept of preadaptation.

1911 Charles Doolittle Walcott (1850-1927) discovers a rich assemblage of invertebrate fossils from the middle Cambrian in the Burgessshale of British Columbia.

1911 Ernest Rutherford (Spring Grove, New Zeeland 1871 - Christchurch, New Zealand 1954) deduced from his previous studies on alpha rays that almost all of the mass of an atom is concentrated in a nucleus a thousand times smaller than the atom itself.

1912 Alfred Lothar Wegener (1880-1930) develops a theory of continental drift based on fossil and glacial evidence. Unfortunately, his theory is ridiculed until long after his death because he could provide no adequate explanation for the cause of the phenomenon.

1912 Carl Neuberg proposes a chemical pathway for fermentation.

1912 T. Thunberg (?-?), and F. Batelli (?-?) and L. S. Stern (?-?) discover that minced animal tissues contain substances that can transfer hydrogen atoms from specific intracellular organic acids to methylene blue dye, reducing it to a colorless form.

1912 Murray and Hjort publish The Depths of the Oceans summarizing their expedition.

1912 Otto Warburg (Freiburg, 1883 - Berlin, 1970) postulates a respiratory enzyme for the activation of oxygen, discoverd its inhibition by cyanide, and shows the requirement of iron in respiration.

1912 J. Friedrich Gudernatsch (?-?) finds that removal of the thyroid gland prevent metamorphosis in frogs, while feeding horse thyroid extracts to young tadpoles induces precocious metamorphosis.

1912 Edward Albert Sharpey-Schäfer (850-1935) coins the term "insuline" for the active principle of the pancreas in the control of blood glucose.

1912 Alexis Carrel develops and publishes the technique of in vitro tissue culture. He also develops techniques for transplantation of organs and an artificial heart.

1912 William Henry Bragg (Westward,, 1862 - Manchester, 1942) and his son William Lawrence Bragg (Adelaide, Australia 1890 - London, 1971) develop the X-ray crystallography technique can be used to study the molecular structure of simple crystalline substanceswhich would laterbe used in the elucidation of the three-dimensional structures of proteins and nucleic acids.

1912 Arthur Smith Woodward (1864-1944) announces with much publicity, the discovery of the Piltdown man, later known as a fake.

1912 Ivan Vladimirovitch Mitchourine (Verchina, Russia 1855 - Kozlov, 1935) discovers the importance of cold for germination of seeds (vernalisation). Together with the theory of the "mentor" (grafts that would "teach" heredity to plants) his serves as a basis for the crazy theory of Trofim Denisovitch Lysenko (1898-1976) about evolution of heredity, with much negative consequences on the development of genetics in the Soviet Union and satellite countries.

1912 Jacques Loeb publishes The Mechanistic Conception of Life.

1912-1922 Heinrich Otto Wieland (Pforzheim, 1877 - München, 1957) demonstrates the activation of hydrogen in dehydrogenation reactions.

1913 Alfred Henry Sturtevant (1891-1971), a student of Morgan, constructs the first gene map by analyzing mating results for fruit flies with six different mutant factors each known to be recessive and X-linked. He traced each mutation and its normal alternate in relation to each of the other mutants, and thus calculated the exact percentage of crossing-over between the genes.

1913 John Broadus Watson (1878-1958) founds the behaviorist school of psychology, which emphasizes the study of observable behavior rather than conscious and unconscious mental processes.

1913 Hans Reck (?-?) discovers rich deposits of early mammalian fossils including Stone Age artifacts and a "human" skeleton in the upper part of Bed II at Olduvai Gorge in Tanzania then German East Africa. The date of the fossils was supposed to be about 1.15 million years old. This triggered a controversy still extant today, since the skull appears to be from a Homo sapiens. However this discovery emphasized the potential interest of this and other connected sites, which were a mine of new discoveries about the origin of Man.

1913 Leonor Michaelis (1875-1940) and Maud Leonora Menten (1879-1960) postulate the existence of an intermediate enzyme-substrate complex to explain themechanism of enzyme action. (Michaelis is also the father of the home permanent, by virtue of his discovery of the solubility of keratin in thioglycolic acid.)

1913 Calvin Blackman Bridges (1889-1938) reports non disjunction of sex chromosomes as a proof of the chromosome theory of heredity.

1913 Creation of the Institut Pasteur at Bangkok, in Thailand. Its activity is mostly devoted to creation and use of vaccine (in particular against rabies, and above all small pox: in seven years it will produce more than ten million doses of the vaccine).

1913 Sturtevant develops the first genetic map by using cross-over frequencies as measurements of relative distances.

1913 Thomas Burr Osborne (New Haven, 1859–1929) and Lafayette Benedict Mendel (1872-1935) show that rats develop xerophthalmia on diets in which lard is the only fat supply, the condition is cured by substitution of butter fat. This leads to the discovery of vitamin A.

1913 Shiro Tashiro (1883-1963) measures slight increases in carbon dioxide production in nerves when they were stimulated.

1913 Publication of Richard Willstätter and Arthur Stoll's (1887-1971) Unterschungen Über Chlorophyll.

1913 Victor Ernest Shelford (1877-1968), working on animal communities, formulates the law of ecologic tolerance.

1913 Frederick Soddy (1877-1956) who had discovered with Rutherford the existence of the radioactive substance decay, coins the word "isotope".

1913 Fritz Shaudinn (1871 - ?) discovers Spirochaete pallida (the causing agent of Syphilis, now know as Treponema pallidum) and by means of experiments on himself he made valuable contributions on Amaeba histolytica and the malaria agent.

1913 Shaudinn's student Stanislaus Joseph Mathias Edler von Lanow Prowazek (1875-1915) continues his work on disease-producing sporozoa.

1913-1925 Francis Bertody Sumner (Pomfret, Connecticut , 1874, La Jolla, California,1945), who had joined the Scripps Institution of Oceanography and studied geographic variation in Peromyscus convinces himself that the apparently continuous variability is actually Mendelian in nature.

1914 Edward Calvin Kendall (South Norwalk, USA 1886 - 1972) completes the final isolation of crystalline thyroxine, the active substance produced by the thyroid gland.

1914 Frank Rattray Lillie (1870–1947) hypothesizes the existence of a substance, fertilizin, in the jelly coat of eggs which causes sperm cells to clump together.

1914 Following many European precursors, Warren Harmon Lewis (1870–?) and his wife, Margaret R. Lewis, (?-?) confirm the existence and provide further description of the organelles found in nucleated cells, the mitochondria.

1914 George Harrison Shull ( Clark County, Ohio,1874 - Princeton, 1954) observes in maize the phenomenon of heterosis, commonly referred to as hybrid vigor. He later creates the scientific journal Genetics.

1915 Joseph Goldberger (1874 - 1929) demonstrates that pellagra, until then widely held to be a hereditary condition, is actually caused by a diet lacking in meat or milk. The exact cause was later determined to be niacin deficiency.

1915 The Mechanism of Mendelian Heredity, an epochal book is published by Morgan, Sturtevant, Calvin Blackman Bridges (1889-1938), and Hermann Joseph Muller (1890-1968)

1915 Felix Hubert d'Hérelle (Montréal, 1873 - Paris, 1949), describes "plages de lyse par des phages" and independently of Twort, describes in 1917 "an invisible microbe", which he calls a bacteriophage, that antagonizes the bacillus that causes dysentery, destroying the bacteria. Bacteriophages (often abbreviated as "phages") cause plaques on bacterial lawns, analogous to colonies on agar plates. Later plaques will prove useful in preparing pure cultures and characterizing different strains of the bacteriophages or bacterial viruses, as well as speed up many of the first steps in genetic engineering techniques.

1915 Wegener publishes his view on continental drift; Die Entstehung der Kontinente und Ozeane.

1916 Frederick Twort (1877-1950) discovers a "disease" of bacteria which he calls "glassy transformation". He shows that the disease agent is transmissible, filterable, invisible with a light microscope and does not grow in the absence of the living host bacterium. Twort further proposes three possible explanations, including a filterable virus and an enzyme.

1916 JP Lotsy (?-?) publishes Qu'est-ce qu'une espèce? in Amsterdam, where he discusses the nature of species in terms of heredity, and not as classes, as done by Linné. For him a species is the sum of all homozygous individuals having the same hereditary character. It therefore becomes a matter of doubt that there is any species in Nature...

1916 Oscar Hertwig publishes Das Werden der Organismen, where he places a strong attack on selective theories and Darwinism, setting the stage for future Lamarckian thoughts, in particular with the infamous Trofim Lysenko in USSR. In parallel, Hertwig develops a cell theory meant to explain all properties of life and evolution the egg containing within itself all the characters of the adult organism (he uses the same term as Nägeli to describe this: idioplasma), maintaining strongly the concept of heredity of acquired characters.

1916 Lillie demonstrates the role of sex hormones in free-martinism in cattle.

1916 Henry Edward Crampton (?-?) describes geographical races of the snail Partula in Tahiti, Moorea and the neighbor islands. He will devote 50 years of his life to the study of this genus, which was unfortunately doomed to disappear because of human activities.

1917 Plough (?-?) demonstrates the rearrangement of chromosomes now known as 'crossing over' rediscovering the "chiasmatypie" of Jenssens. This is one among the multiples cases of rediscoveries with name changes, that induce people in putting too much emphasis on some places or names in the continuous progress of science. This process is unfortunately much used today as a manipulation to attribute discoveries to people others than those who actually made them.

1917 Stefan Kopec (Poland ?-?) in experiments which were overlooked at first, discovers the role of the brain in insect metamorphosis, paving the way for the identification of ecdysone, a steroid neurohormone.

1917 In the bitter days of the Great War, Hertwig attacks the theory of the struggle for existence and natural selection in a polemical article, Zur Abwehr des ethischen, des sozialen, des politischen Darwinismus. This triggers a furious debate which is not closed today. Despite his lack of solid theoretical background Hertwig's attack on the widely spread use of Darwinism by a number of writers, biologists with a deficient social grounding, newspaper-men and political authors of various kinds points to inescapable weaknesses in the sheer extension of simplified (not well understood) Darwinism to social behaviour, where woolly thinkers mix up ethics, politics and science.

1917 D'Arcy Wentworth Thompson (Edinburgh,1860 - St Andrews, 1948) publishes his book On Growth and Form, which was highly influential for perpetuating an instructive model of ontogenesis of forms in multicellular organisms.

1917 Ferdinand Broili (1874-?) discovers the fossil remains of Seymouria, an organism showing both amphibian and reptilian characteristics.

1917 Joseph Grinnell (?-1939) an ornithologist who is often associated with starting the evolution of the modern idea of the ecological niche because he suggests that year that animal niches can be defined by feeding preferences and habitat associations and that two species cannot overlap completely in both habitat preference and their feeding preference.

1917 Yersin begins to plant quinquina in Viêt-Nam, to produce quinine, against malaria. The production increases rapidly to reach 29600 tons and 2045 kg of quinine sulfate in 1936.

1917 Emerson further discovers and analyzes variegated pericarp, a highly mutable gene in maize. After thirty-five years this gene is still under active study.

1917 Elmer Verner McCollum (1879-1967) and Simmonds (?-?) study the influence of diet in health and show that xerophthalmia in rats is due to lack of a fat-soluble substance which they name vitamine A.

1917 Richard Goldschmidt and L. T. Troland (?-?) propose the (inaccurate) view that genes are enzymes. This was later influential in retarding the discovery of DNA as the genetic material.

1917-1918 Sewall Wright (1889-1988), following similar lines as Cuénot, develops the analysis of the inheritance of coat colors in guinea pigs, mice, rats, rabbits, horses, and other mammals. He shows that production of the pigment determining coat color in mammals requires biochemical steps, taking place in fixed temporal order. He suggests that each step is mediated by a different, specific enzyme. He further begins to create inbred lineages of rodents.

1918 Herbert Mclean Evans (?-?) states (incorrectly) that human cells contain 48 chromosomes.

1918 Loeb introduces the concepts of "forced movements", "tropisms" and "animal conduct". He vehemently opposes any anthropomorphic or teleological interpretations of animal behavior.

1918 Paul Portier, who had worked with Richet, publishes his influential book, Les Symbiotes, which describes mitochondria as bacterial endosymbionts of cells. In this book he states that tthat all organisms are formed by the association of two different kinds of creatures. All cells are supposed to contain bacteria that are needed for them to live. His views are challenged by but spread rapidly, in particular in the USA, where they are revived in the 1960s.

1918 Ernest Starling recognizes that the greater the volume of blood entering the ventricles of the heart, the greater theforce of contraction and states that "The law of the heart is thus the same as the law of muscular tissue generally, that the energy of contraction, however measured, is a function of the length of the muscle fibre."

1918 August Krogh (Grenaa, Denmark, 1874 - Copenhagen, 1949) shows that capillaries are capable of contracting or dilating due to chemical or nervous controls.

1918 J. S. Szymanski (?-?) shows that animals were capable of maintaining 24-hour activity patterns in the absence of external cues such as light and temperature. These are now known as "circadian rhythms", or the "biological clock".

1918 Nikolay Ivanovich Vavilov (Moscou, 1887 - died of hunger in the jail of Saratov on the Volga, 1943) in his "Immunity of Plants to Infectious Diseases" stresses the importance of geographic centers of origin as reservoirs of desirable genes which can be incorporated into cultivated strains derived from those regions. The head ot the Russian school of genetics and a remarkable scientist, Vavilov was later to suffer under Trofim Lyssenko's pseudo-lamarckian dictatorship.

1919 Jack Cecil Drummond (1891 - 1952) names vitamin C, and changes the spelling from the German and French vitamine to vitamin. This is a typical example of the role of nominalism in science, with important socio-political implications (in particular about the memory of discoveries, plagiarism and the like). He states that "The dietary requirements of the higher animals include in addition to a satisfactorily balanced ration of protein, fats, carbohydrate and mineral salts, an adequate supply of three accessory food factors: 1. Fat-soluble A. 2. Water-soluble B, or antineuritic factor. 3. Water-soluble C, or antiscorbutic factor."

1919 Francis William Aston (Birmingham, England, 1877 - Cambridge, 1945) discovers that atoms occur in different isotopes. Rare isotopes have been used as tracers in the study of biological processes since 1923.

1919 Edward Mellanby (1884 -1955) searching for a dietary deficiency as the cause of rickets, had decided in 1918 to test porridge, the staple food of Scotland, by feeding dogs exclusively on oats. This triggered another example of serendipity: inadvertently, he had also kept the animals indoors throughout the experiment, thereby inducing rickets. He subsequently cures the dogs of the disease by feeding them cod-liver oil. This naturally but wrongly led him to credit the oil's recently identified vitamin A with the cure.produces experimental rickets in puppies still searching for a dietary deficiency as the cause of rickets.

1919 At the Institut Pasteur du Brabant in Bruxelles, Jules Bordet and his colleague August von Wasserman (?-?) establish the Bordet-Wasserman test for the diagnosis of syphilis.

1919 K. Huldschinsky (? Germany -?) carries out a remarkably innovative experiment and cures children of rickets using artificially-produced ultraviolet light.

1919 Wilbur Willis Swingle (?-?) reproduces Gudernatsch's results on metamorphosis in frogs by providing or withholding inorganic iodine.

1919 A. Paál (?Hungary, -?) shows that when the tip of a plant shoot is cut off and replaced to one side, the growth of the base is greater on this side. the substance stimulating growth was driven away from light, by removing coleoptile tips and replacing them to
one side of the coleoptile. This resulted in growth on the side in contact with the tip.

1919 Otto Warburg discovers that the efficiency of photosynthesis is increased in intermittent light.

1919 Morgan and coworkers publish The Physical Basis of Heredity, a summary of the rapidly growing findings in genetics, ending in a somewhat dogmatic view, that prevented further immediate developments in the concepts of cytoplasmic heredity.

1919-1920 Harry Steenbock (1886-1967) establishes the relationship between vitamin A activity and the plant pigment carotene.

Some significant dates 1920-1939

1875-1899

1920-1939

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