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John von Neumann's Cellular Automata

Cellular automata (CA) are mathematical models used to simulate complex systems or processes. In several fields, including biology, physics, and chemistry, CA are employed to analyze phenomena such as the growth of plants, DNA evolution, and embryogenesis. In the 1940s John von Neumann formalized the idea of cellular automata in order to create a theoretical model for a self-reproducing machine. Von Neumann's work was motivated by his attempt to understand biological evolution and self-reproduction.

Format: Articles

Subject: Theories

John von Neumann (1903-1957)

John von Neumann was a Hungarian mathematician who made important contributions to mathematics, physics, computer science, and the area of artificial life. He was born in Budapest, Hungary, on 28 December 1903. His mother was Margit von Neumann and his father was Max von Neumann. His work on artificial life focused on the problem of the self-reproduction of machines. Von Neumann initially discussed self-reproducing machines in his Hixon Symposium paper "The General and Logical Theory of Automata" published in 1948.

Format: Articles

Subject: People

Syncytial Theory

The syncytial theory of neural development was proposed by Victor Hensen in 1864 to explain the growth and differentiation of the nervous system. This theory has since been discredited, although it held a significant following at the turn of the twentieth century. Neural development was well studied but poorly understood, so Hensen proposed a simple model of development. The syncytial theory predicted that the nervous system was composed of many neurons with shared cytoplasm.

Format: Articles

Subject: Theories

The Gradient Theory

The gradient theory is recognized as Charles Manning Child's most significant scientific contribution. Gradients brought together Child's interest in development and his fascination with the origins of individuality and organization. The gradient theory grew from his studies of regeneration, which were largely based on work he conducted with marine invertebrates, such as the ascidian flat worm, planaria and the hydroid, tubularia.

Format: Articles

Subject: Theories

St. George Jackson Mivart (1827-1900)

St. George Jackson Mivart studied animals and worked in England during the nineteenth century. He also proposed a theory of organismal development that he called individuation, and he critiqued Charles Darwin's argument for evolution by natural selection. His work on prosimians, a group of primates excluding apes and monkeys, helped scientists better investigate the Primate group.

Format: Articles

Subject: People

Charles Darwin's Theory of Pangenesis

In 1868 in England, Charles Darwin proposed his pangenesis theory to describe the units of inheritance between parents and offspring and the processes by which those units control development in offspring. Darwin coined the concept of gemmules, which he said referred to hypothesized minute particles of inheritance thrown off by all cells of the body. The theory suggested that an organism's environment could modify the gemmules in any parts of the body, and that these modified gemmules would congregate in the reproductive organs of parents to be passed on to their offspring.

Format: Articles

Subject: Theories

The Formation of Reticular Theory

In the nineteenth century, reticular theory aimed to describe the properties of neurons, the specialized cells which make up the nervous system, but was later disconfirmed by evidence. Reticular theory stated that the nervous system was composed of a continuous network of specialized cells without gaps (synapses), and was first proposed by researcher Joseph von Gerlach in Germany in 1871.

Format: Articles

Subject: Theories

Amphioxus, and the Mosaic Theory of Development (1893), by Edmund Beecher Wilson

Edmund Beecher Wilson experimented with Amphioxus (Branchiostoma) embryos in 1892 to identify what caused their cells to differentiate into new types of cells during the process of development. Wilson shook apart the cells at early stages of embryonic development, and he observed the development of the isolated cells. He observed that in the normal development of Amphioxus, all three main types of symmetry, or cleavage patterns observed in embryos, could be found. Wilson proposed a hypothesis that reformed the Mosaic Theory associated with Wilhelm Roux in Germany.

Format: Articles

Subject: Experiments

Etienne Geoffroy Saint-Hilaire (1772-1844)

Etienne Geoffroy Saint-Hilaire, commonly known as Geoffroy, studied animals, their anatomy and their embryos, and teratogens at the National Museum of Natural History in Paris, France in the eighteenth and nineteenth centuries. Geoffroy also helped develop several specialized fields in the life sciences, including experimental embryology. In his efforts to experimentally demonstrate the theory of recapitulation, Geoffroy developed techniques to intervene in the growth of embryos to see whether they would develop into different kinds of organisms.

Format: Articles

Subject: People

Experimental Studies on Germinal Localization (1904), by Edmund B. Wilson

At the turn of the twentieth century, Edmund B. Wilson
performed experiments to show where germinal
matter was located in molluscs. At Columbia University in New York City,
New York, Wilson studied what causes cells to differentiate during
development. In 1904 he conducted his experiments on molluscs, and he modified the
theory about the location of germinal matter in the succeeding years. Wilson and others modified the
theory of germinal localization to accommodate results that showed

Format: Articles

Subject: Experiments

Rudolf Carl Virchow (1821-1902)

Rudolf Carl Virchow lived in nineteenth century Prussia, now Germany, and proposed that omnis cellula e cellula, which translates to each cell comes from another cell, and which became and fundamental concept for cell theory. He helped found two fields, cellular pathology and comparative pathology, and he contributed to many others. Ultimately Virchow argued that disease is caused by changes in normal cells, also known as cellular pathology.

Format: Articles

Subject: People

Theophilus Shickel Painter (1889-1969)

Theophilus Shickel Painter studied the structure and
function of chromosomes in the US during in the early to mid-twentieth century. Painter worked at
the University of Texas at Austin in Austin, Texas. In the 1920s
and 1930s, Painter studied the chromosomes of the salivary gland
giant chromosomes of the fruit fly (Drosophila
melanogaster), with Hermann J. Muller. Muller and Painter
studied the ability of X-rays to cause changes in the chromosomes
of fruit flies. Painter also studied chromosomes in mammals.

Format: Articles

Subject: People

Lynn Petra Alexander Sagan Margulis (1938-2011)

Lynn Petra Alexander Sagan Margulis was an American biologist, whose work in the mid-twentieth century focused on cells living together in a mutually advantageous relationship, studied cells and mitochondria in the US during the second half of the twentieth century. She developed a theory for the origin of eukaryotic cells, that proposed two kinds of structures found in eukaryotic cells mitochondria in animals, and plastids in plantsÑwere once free-living bacteria that lived harmoniously and in close proximity to larger cells, a scenario called symbiosis.

Format: Articles

Subject: People, Theories

The Origin of Species: "Chapter Thirteen: Mutual Affinities of Organic Beings: Morphology: Embryology: Rudimentary Organs" (1859), by Charles R. Darwin

Mutual Affinities of Organic Beings: Morphology: Embryology: Rudimentary Organs is the thirteenth chapter of Charles Darwin's book The Origin of Species, first published in England in 1859. The book details part of Darwin's argument for the common ancestry of life and natural selection as the cause of speciation. In this chapter, Darwin summarizes the evidence for evolution by connecting observations of development in organisms to the processes of natural selection.

Format: Articles

Subject: Publications

Alexis Carrel's Immortal Chick Heart Tissue Cultures (1912-1946)

In an effort to develop tissue culture techniques for long-term tissue cultivation, French surgeon and biologist Alexis Carrel, and his associates, produced and maintained a series of chick heart tissue cultures at the Rockefeller Institute in New York City. From 1912 to 1946, this series of chick heart tissue cultures remained alive and dividing. Since the duration of this culture greatly exceeded the normal chick life span, the cells were deemed immortal.

Format: Articles

Subject: Experiments

The Germ-Plasm: a Theory of Heredity (1893), by August Weismann

Friedrich Leopold August Weismann published Das
Keimplasma: eine Theorie der Vererbung (The Germ-Plasm: a
Theory of Heredity, hereafter The Germ-Plasm) while
working at the University of Freiburg in Freiburg, Germany in 1892.
William N. Parker, a professor in the University College of South
Wales and Monmouthshire in Cardiff, UK, translated The
Germ-Plasm into English in 1893. In The Germ-Plasm,
Weismann proposed a theory of heredity based on the concept of the

Format: Articles

Subject: Publications, Theories

Germ Layers

A germ layer is a group of cells in an embryo that interact with each other as the embryo develops and contribute to the formation of all organs and tissues. All animals, except perhaps sponges, form two or three germ layers. The germ layers develop early in embryonic life, through the process of gastrulation. During gastrulation, a hollow cluster of cells called a blastula reorganizes into two primary germ layers: an inner layer, called endoderm, and an outer layer, called ectoderm.

Format: Articles

Subject: Theories, Processes

"The Cell-Theory" (1853), by Thomas Henry Huxley

The Cell-Theory was written by Thomas Henry Huxley in Britain and published in 1853 by The British and Foreign Medico-Chirurgical Review. The twenty-two page article reviews twelve works on cell theory, including those in Germany by Caspar Friedrich Wolff in the eighteenth century and by Karl Ernst von Baer in the nineteenth century. Huxley spends much of The Cell-Theory on a cell theory proposed in the late 1830s by Matthias Schleiden and Theodor Schwann in Germany.

Format: Articles

Subject: Publications

Early Infantile Autism and the Refrigerator Mother Theory (1943-1970)

In 1943, child psychiatrist Leo Kanner in the US gave the first account of Early Infantile Autism that encouraged psychiatrists to investigate what they called emotionally cold mothers, or refrigerator mothers. In 1949, Kanner published Problems of Nosology and Psychodynamics of Early Infantile Autism. In that article, Kanner described autistic children as reared in emotional refrigerators. US child psychiatrists claimed that some psychological or behavioral conditions might have origins in emotional or mental stress, meaning that they might be psychogenic.

Format: Articles

Subject: Disorders, Theories

Walter Stanborough Sutton (1877-1916)

Walter Stanborough Sutton studied grasshoppers and connected the phenomena of meiosis, segregation, and independent assortment with the chromosomal theory of inheritance in the early twentieth century in the US. Sutton researched chromosomes, then called inheritance mechanisms. He confirmed a theory of Wilhelm Roux, who studied embryos in Breslau, Germany, in the late 1880s, who had argued that chromosomes and heredity were linked. Theodor Boveri, working in Munich, Germany, independently reached similar conclusions about heredity as Sutton.

Format: Articles

Subject: People

A Treatise on the Theory and Practice of Midwifery (1752-1764), by William Smellie

A Treatise on the Theory and Practice of Midwifery is a three volume collection of patient accounts that William Smellie published from 1752 to 1764. Smellie, a physician and instructor in obstetrics in Great Britain, published these compilations to share his expertise in reproductive medicine, while also providing his students and colleagues with a source of reference in their own medical practices. Smellie wrote these books to shift obstetrics from a discipline practiced by midwives with limited medical training to one practiced in a medical context by physicians.

Format: Articles

Subject: Publications

A Treatise on the Theory and Practice of Midwifery, (1752-1764) by William Smellie

A Treatise on the Theory and Practice of Midwifery is a three volume collection of patient accounts that William Smellie published from 1752 to 1764. Smellie, a physician and instructor in obstetrics in Great Britain, published these compilations to share his expertise in reproductive medicine, while also providing his students and colleagues with a source of reference in their own medical practices. Smellie wrote these books to shift obstetrics from a discipline practiced by midwives with limited medical training to one practiced in a medical context by physicians.

Format: Articles

"Gene Regulation for Higher Cells: A Theory" (1969), by Roy J. Britten and Eric H. Davidson

In 1969, Roy J. Britten and Eric H. Davidson published Gene Regulation for Higher Cells: A Theory, in Science. A Theory proposes a minimal model of gene regulation, in which various types of genes interact to control the differentiation of cells through differential gene expression. Britten worked at the Carnegie Institute of Washington in Washington, D.C., while Davidson worked at the California Institute of Technology in Pasadena, California. Their paper was an early theoretical and mechanistic description of gene regulation in higher organisms.

Format: Articles

Subject: Publications

Calvin Bridges’ Experiments on Nondisjunction as Evidence for the Chromosome Theory of Heredity (1913-1916)

From 1913 to 1916, Calvin Bridges performed experiments that indicated genes are found on chromosomes. His experiments were a part of his doctoral thesis advised by Thomas Hunt Morgan in New York, New York. In his experiments, Bridges studied Drosophila, the common fruit fly, and by doing so showed that a process called nondisjunction caused chromosomes, under some circumstances, to fail to separate when forming sperm and egg cells. Nondisjunction, as described by Bridges, caused sperm or egg cells to contain abnormal amounts of chromosomes.

Format: Articles

Subject: Experiments, Publications

Johann Friedrich Meckel, the Younger (1781-1833)

Johann Friedrich Meckel studied abnormal animal and human anatomy in nineteenth century Germany in an attempt to explain embryological development. During Meckel's lifetime he catalogued embryonic malformations in multiple treatises. Meckel's focus on malformations led him to develop concepts like primary and secondary malformations, atavism, and recapitulation- all of which influenced the fields of medicine and embryology during the nineteenth and twentieth centuries.

Format: Articles

Subject: People

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