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.

The United States Food and Drug Administration, or FDA, published 'General Considerations for the Clinical Evaluation of Drugs,' in September 1977. The document defined acceptable practices for investigators who studied new drugs. Specifically, the document outlined the common clinical trial methods. Clinical trials are studies to test whether a new drug is safe before doctors can prescribe it to patients. Prior to 1977, the Protection of Human Subjects Rule primarily regulated clinical drug trials, but it did not specify who could and could not be included in clinical trials. In the document, the FDA recommended that anyone who could become pregnant be excluded from early-phase clinical trials to minimize risks to a potential fetus. After the FDA published the document, investigators excluded women from clinical trials. The document ultimately prevented women of reproductive capacity from participating in early phase clinical trials, which affected women’s health research.

Charles Knowlton was a physician and author who advocated for increased access to information about reproduction in the nineteenth century in the US. Throughout his early medical education, Knowlton was particularly interested in anatomy and on several instances robbed graves for bodies to dissect. In 1832, Knowlton authored The Fruits of Philosophy, a pamphlet that contained detailed descriptions of the reproductive organs and information on conception and methods to control reproduction. Knowlton circulated his work among his patients until it was republished in Boston, Massachusetts, in 1832. For publishing a book on sex and methods of birth control, Knowlton was convicted of breaking obscenity laws, which prevented the transmission of obscene materials. After his death, social activists Charles Bradlaugh and Annie Besant republished his work in London, England. Knowlton’s writing about sex and birth control allowed individuals to understand and take control of their reproduction and initiated a public discussion about obscenity laws.

In 1993, the NIH published the Revitalization Act that established guidelines for minorities’ and women’s participation in clinical research. Before the 1990s, investigators largely excluded women from their research based on the 1979 guidance from the US Food and Drug Administration, or FDA. The FDA urged investigators to exclude any woman who was or could become, pregnant to protect the woman and any developing fetuses from harm. Between 1979 and 1993, several other US governmental agencies urged investigators to increase the number of women in their clinical research to improve the state of women’s healthcare. After Congress passed the National Institutes of Health Revitalization Act, hereafter Revitalization Act of 1993, investigators who used NIH funds for clinical research were required to include both women and minorities in their clinical research. The Revitalization Act established the Office of Research on Women’s Health headquartered in Washington, DC and required investigators to include women in their clinical research, thus improving the quality of women’s health research.

Annie Wood Besant was a social activist who advocated for women’s access to birth control as well as marriage reform, labor reform, and Indian Nationalism in the nineteenth century in England and India. In her early career, Besant was involved in various social and political advocacy organizations including the National Secular Society, the Malthusian League, and the Fabian Society. Besant gave many public lectures and authored various articles in support of secularism, workers’ rights and unionization, and women’s rights. In 1877, Besant and her colleague Charles Bradlaugh republished the pamphlet The Fruits of Philosophy, by Charles Knowlton, on reproduction and contraception. Besant and Bradlaugh were tried for violating the obscenity law that prohibited the publication of obscene material, including sex and contraception. Later in her life, she converted to theosophy and moved to India where she joined the Theosophical Society. In India, Besant campaigned for Indian self-rule and became the president of the Indian National Congress. Besant, through republication of The Fruits of Philosophy and many public lectures and writings on women’s rights, expanded public knowledge of birth control.

Charles Bradlaugh was as a political and social activist in the seventeenth century in England. He held leadership positions in various organizations focused on social and political activism including the Reform League, the London Secular Society, the newspaper National Reformer, and the National Secular Society. Throughout his career, Bradlaugh advocated for better conditions for the working poor, and for the separation of government and religion. The British government prosecuted him numerous times for violating laws prohibiting the publication, sale, and transmission of antireligious, antigovernment, and obscene materials. In 1877, Bradlaugh and another secularist, Annie Besant, republished The Fruits of Philosophy, a pamphlet about contraceptive techniques originally whose author was physician Charles Knowlton. In the nineteenth century, individuals did not have access to information on sex, reproduction, and contraception, as much of society argued such information encouraged immoral behavior. Bradlaugh and Besant were tried for publishing information on sexual anatomy, conception, and methods to control reproduction. Bradlaugh expanded public knowledge of reproduction and contraception, and initiated the process of dismantling the obscenity laws.

Marcello Malpighi studied chick embryos with microscopes in Italy during the seventeenth century. Trained as a medical doctor, he was among the first scientists to use the microscope to examine embryos at very early stages. Malpighi described early structures in chick embryos, and later scientists used his descriptions to help develop the theory of preformationism.