Embryo Project Encyclopedia

Ovism was one of two models of preformationism, a theory of generation prevalent in the late seventeenth through the end of the eighteenth century. Contrary to the competing theory of epigenesis (gradual emergence of form), preformationism held that the unborn offspring existed fully formed in the eggs or sperm of its parents prior to conception. The ovist model held that the maternal egg was the location of this preformed embryo, while the other preformationism model known as spermism preferred the paternal germ cell, as the name implies.

This embryology image is a pencil sketch by Nicolaas Hartsoeker, published as part of his 1694 French-language paper entitled Essai de Dioptrique, a semi-speculative work describing the sorts of new scientific observations that could be done using magnifying lenses. Dioptrique was published in Paris by the publishing house of Jean Anisson. The image depicts a curled up infant-like human, now referred to as a homunculus, inside the head of a sperm cell. This sketch is important to embryology because it is one of the most illustrative examples of preformationism, a theory of generation stating that each future member of any given species exists, fully formed though miniscule, within the gametic cells (sperm or eggs) of its parents. This theory was popular among naturalists in the eighteenth century.

Nicolaas Hartsoeker, a Dutch astronomer, optics manufacturer, and naturalist, was born 26 March 1656 in Gouda, Netherlands, and died 10 December 1725. His mother was Anna van der Mey and his father was Christiaan Hartsoeker, a prominent evangelical minister. His major contribution to embryology was his observations of human sperm cells, which he claimed to be the first to see under a microscope. His sketch of the homunculus, a tiny preformed human he believed to exist in the head of spermatazoa, is his lasting scientific legacy in the field of embryology. This sketch was only a minor part of his first publication, Essai de Dioptrique (1694), which dealt primarily with the use of optical lenses in science. In subsequent years the sketch became iconic of the theory of embryological development known now as preformationism. Hartsoeker himself was a vocal adherent of spermist preformationism and is often cited as the originator of the idea.

Preformationism was a theory of embryological development used in the late seventeenth through the late eighteenth centuries. This theory held that the generation of offspring occurs as a result of an unfolding and growth of preformed parts. There were two competing models of preformationism: the ovism model, in which the location of these preformed parts prior to gestation was the maternal egg, and the spermism model, in which a preformed individual or homunculus was thought to exist in the head of each sperm. Preformationism was a widely-held theory by Enlightenment-era scientists, but by the early 1800s, most scientists had abandoned it, in part because higher magnification in microscopes enabled them to see the very earliest stages of embryos as small collections of cells. Prior to preformationism, naturalists who studied embryo development favored the theory of spontaneous generation in lower animals, such as flies, which appeared to arise from manure. In higher animals, however, scientists used the theory of epigenesis put forth by Aristotle, who said that maternal and paternal fluids came together in the uterus and solidified during early gestation into a fetus. Preformationism was the first theory of generation and development that applied to all organisms in the plant and animal kingdoms.

In 2012, Jennifer Doudna, Emmanuelle Charpentier from the University of California, Berkeley, in Berkeley, California, and Umeå University in Umeå, Sweden, along with their colleagues discovered how bacteria use the CRISPR/cas 9 system to protect themselves from viruses. The researchers also proposed the idea of using the CRISPR/cas 9 system as a genome editing tool. In bacteria and archaea, researchers had found that CRISPR, which stands for clustered regularly interspaced short palindromic repeats, and CRISPR associated proteins, or cas, helped organisms recognize and silence the genetic material of viruses that have infected the cell before. In their experiment, Doudna, Charpentier, and their colleagues found how the specific molecules in bacteria can recognize and cut specific DNA sequences of invading viruses. Doudna, Charpentier, and their colleagues’ discovery of the CRISPR/cas 9 mechanism and proposal of using CRISPR/cas 9 for genetic editing led to the successful engineering of CRISPR/cas 9 as a novel method of editing genomes.

In 1949, Priscilla White published Pregnancy Complicating Diabetes, which described the results and implications of a fifteen-year study about pregnant diabetic women. Published in the American Journal of Medicine, the article details possible causes of and ways to prevent the high fetal mortality rate associated with pregnant diabetic women. Diabetes is a disease in which the body's ability to produce or respond to the hormone insulin is impaired, and it can be particularly dangerous during pregnancies. In her article, White reported that prematurely delivering infants for diabetic pregnant women reduces infant and maternal mortality rates. Pregnancy Complicating Diabetes helped make premature delivery of infants the standard of care for diabetic pregnant women, and it has contributed to the increased survival rate of infants born from diabetic mothers from less than fifty percent in the 1940s to over ninety percent in 2017.

In the 1983 case City of Akron v. Akron Center for Reproductive Health the US Supreme Court ruled that certain requirements of the city of Akron’s “Regulation on Abortion” ordinance violated women’s rights to abortions. Despite the legalization of abortion in the 1973, with the US Supreme Court case Roe v. Wade, individual states passed legislation regulating certain aspects of abortion. The city of Akron, Ohio, passed legislation in 1978 that regulated when and where abortions could be conducted, the consent process leading up to abortions, and the disposal of fetal remains after abortions. In a six to three ruling, the Court argued provisions of the city of Akron’s ordinance were unconstitutional. The Court’s opinion in City of Akron v. Akron Center for Reproductive Health reaffirmed the ruling in Roe v. Wade that states could not unduly restrict women’s access to abortions.

What Every Girl Should Know was published in 1916 in New York City, New York, as a compilation of articles written by Margaret Sanger from 1912 to 1913. The original articles appeared in the newspaper New York Call, under the tile “What Every Girl Should Know.” The articles, which are organized into chapters and individual parts in the book, describe sex education, human reproduction, and sexually transmitted infections. Sanger, a nurse and social activist, published What Every Girl Should Know during a time in which US federal and state obscenity laws regulated the circulation of literature related to sex. What Every Girl Should Know flouted those laws, helping people to learn about sex education and reproductive health in the US during the early twentieth century.

What Every Mother Should Know was published in 1914 in New York City, New York, as a compilation of newspaper articles written by Margaret Sanger in 1911. The series of articles informed parents about how to teach their children about reproduction and it appeared in the newspaper New York Call. In 1911, the newspaper series was published as a book, with several subsequent editions appearing later. In What Every Mother Should Know, Sanger emphasizes starting education on reproduction early and honestly answering children’s questions. The book acted as a resource for parents and urged readers to be less fearful of approaching the topic with their children. What Every Mother Should Know provided information to the public about sex education and reproductive health, which was scarce during the early twentieth century.

In 1984, Dante Cicchetti published “The Emergence of Developmental Psychopathology,” an article in which he argued that the previously amorphous study of developmental psychopathology was emerging as a unified discipline. According to Cicchetti, developmental psychopathology describes an interdisciplinary field that studies abnormalities in psychological function that can arise during human development. Such studies include research about the effects that traumatic experiences may have on the development of psychological disorders and about what behaviors are considered normal or abnormal at different ages. In the article, Cicchetti reports about the origins of developmental psychopathology, why it emerged as its own discipline, and why researchers should study it. In addition to recognizing the field of developmental psychopathology, the article informed later research about preventing and treating the harmful psychological effects of early traumatic events.