Embryo Project Encyclopedia

The principal work of St. Thomas Aquinas, the Summa Theologica is divided into three parts and is designed to instruct both beginners and experts in all matters of Christian Truth. It discusses topics central to Christian morality, ethics, law, and the life of Christ, providing philosophical and theological solutions to common arguments and questions surrounding the Christian faith. The views presented in this body of writing are currently upheld in large part by the modern doctrines of the Roman Catholic Church. Interesting references to and insights on ensoulment and embryology, as well as other topics discussed in Summa Theologica, indicate a strong Aristotelian and Augustinian influence.

As the third director of the Carnegie Institute of Washington s Department of Embryology, George Washington Corner made a number of contributions to the life sciences as well as to administration. Corner was born on 12 December 1889 in Baltimore, Maryland, near the newly established Johns Hopkins University. Although Corner was not exposed to science much in school at a young age, he developed an early appreciation for science through conversations with his father about geography and by looking through the family's National Geographic magazines.

Stanley Cohen is a biochemist who participated in the discovery of nerve growth factor (NGF) and epidermal growth factor (EGF). He shared the 1986 Nobel Prize in Physiology or Medicine with Rita Levi-Montalcini for their work on the discovery of growth factors. His work led to the discovery of many other growth factors and their roles in development.

Karl Wilhelm Theodor Richard von Hertwig is an important figure in the history of embryology for his contributions of artificial hybridization of sea urchin eggs and the formulation of his coelom theory. He was born 23 September 1850 in Friedelberg, Germany, to Elise Trapp and Carl Hertwig. Richard and his older brother Oscar began their studies at Jena under the direction of Ernst Haeckel from 1868 to 1871. In 1872 Hertwig became a lecturer in zoology at Jena while Oscar lectured in anatomy and embryology. As both brothers advanced in their respective fields, Hertwig left Jena to become a professor at Königsberg. In 1883 he was professor at Bonn and in 1885 in Munich, where he stayed until his retirement in 1925. Hertwig married Julia Braun in 1887 and had two sons and one daughter. He remained very active his entire life, outliving his brother Oscar by fifteen years.

Libbie Henrietta Hyman was born into a recently immigrated Jewish family on 6 December 1888 in Des Moines, Iowa. One of many siblings and daughter to parents Sabina Neumann and Joseph Hyman, who did not particularly support her interests in science, Hyman excelled in school and indulged her interests in biology in her free time. From a young age, Hyman collected and cataloged flora around her home. Despite being valedictorian of her high school class, Hyman's first job was labeling cereal boxes in a local factory. It was only when a former teacher became aware of Hyman's situation that Hyman was prompted to apply for college scholarships.

In February 1953, Linus Pauling and Robert Brainard Corey, two scientists working at the California Institute of Technology in Pasadena, California, proposed a structure for deoxyribonucleic acid, or DNA, in their article “A Proposed Structure for the Nucleic Acids,” henceforth “Nucleic Acids.” In the article, Pauling and Corey suggest a model for nucleic acids, including DNA, that consisted of three nucleic acid strands wound together in a triple helix. “Nucleic Acids” was published in Proceedings of the National Academy of Sciences shortly after scientists came to the consensus that genes, the biological factors that control how organisms develop, contained DNA. Though scientists proved Pauling and Corey’s model incorrect, “Nucleic Acids” helped scientists understand DNA’s structure and function as genetic material.

In April 1953, James Watson and Francis Crick published “Molecular Structure of Nucleic Acids: A Structure of Deoxyribose Nucleic Acid” or “A Structure for Deoxyribose Nucleic Acid,” in the journal Nature. In the article, Watson and Crick propose a novel structure for deoxyribonucleic acid or DNA. In 1944, Oswald T. Avery and his group at Rockefeller University in New York City, New York published experimental evidence that DNA contained genes, the biological factors called genes that dictate how organisms grow and develop. Scientists did not know how DNA’s function led to the passage of genetic information from cell to cell, or organism to organism. The model that Watson and Crick presented connected the concept of genes to heredity, growth, and development. As of 2018, most scientists accept Watson and Crick’s model of DNA presented in the article. For their work on DNA, Watson and Crick shared the 1962 Nobel Prize in Physiology or Medicine with Maurice Wilkins.

Max Ludwig Henning Delbrick applied his knowledge of theoretical physics to biological systems such as bacterial viruses called bacteriophages, or phages, and gene replication during the twentieth century in Germany and the US. Delbrück demonstrated that bacteria undergo random genetic mutations to resist phage infections. Those findings linked bacterial genetics to the genetics of higher organisms. In the mid-twentieth century, Delbrück helped start the Phage Group and Phage Course in the US, which further organized phage research. Delbrück also contributed to the DNA replication debate that culminated in the 1958 Meselson-Stahl experiment, which demonstrated how organisms replicate their genetic information. For his work with phages, Delbrück earned part of the 1969 Nobel Prize for Physiology or Medicine. Delbrück's work helped shape and establish new fields in molecular biology and genetics to investigate the laws of inheritance and development.

In 1954 Max Delbruck published On the Replication of Desoxyribonucleic Acid (DNA) to question the semi-conservative DNA replication mechanism proposed that James Watson and Francis Crick had proposed in 1953. In his article published in the Proceedings of the National Academy of Sciences, Delbrück offers an alternative DNA replication mechanism, later called dispersive replication. Unlike other articles before it, On the Replication presents ways to experimentally test different DNA replication theories. The article sparked a debate in the 1950s over how DNA replicated, which culminated in 1957 and 1958 with the Meselson-Stahl experiment supporting semi-conservative DNA replication as suggested by Watson and Crick. On the Replication played a major role in the study of DNA in the 1950s, a period of time during which scientists gained a better understanding of DNA as a whole and its role in genetic inheritance.

In 1956, Gunther Stent, a scientist at the University of California Berkeley in Berkeley, California, coined the terms conservative, semi-conservative, and dispersive to categorize the prevailing theories about how DNA replicated. Stent presented a paper with Max Delbrück titled “On the Mechanism of DNA Replication” at the McCollum-Pratt Symposium at Johns Hopkins University in Baltimore, Maryland. In response to James Watson and Francis Crick’s proposed structure of DNA in 1953, scientists debated how DNA replicated. Throughout the debate, scientists hypothesized different theories about how DNA replicated, but none of the theories had sound experimental data. Stent introduced DNA replication classes that, if present in DNA, would yield distinct experimental results. Conservative, semi-conservative, and dispersive DNA replication categories shaped scientists' research into how DNA replicated, which led to the conclusion that DNA replicated semi-conservatively.