Embryo Project Encyclopedia

In 1973, Ronald Ericsson developed the Ericsson method, which is a technique used to separate human male sperm cells by their genetic material. Ericsson, a physician and reproduction researcher, developed the method while conducting research on sperm isolation in Berlin, Germany, in the early 1970s. He found that the sperm cells that carry male-producing Y chromosomes move through liquid faster than the cells that carry female-producing X chromosomes. As a result of his findings, Ericsson suggested suspending a semen sample in a viscous liquid made from albumin protein, and collecting only sperm that quickly pass through the liquid. Shortly after Ericsson described his method, researchers demonstrated that it was effective for sex selection. However, later studies contested those results. Despite that, the Ericsson method is still utilized by couples in 2018 as a means of sex selection and was the first sperm separation technique used in combination with artificial insemination to enable people to select the sex of their children.

Torsten Nils Wiesel studied visual information processing and development in the US during the twentieth century. He performed multiple experiments on cats in which he sewed one of their eyes shut and monitored the response of the cat’s visual system after opening the sutured eye. For his work on visual processing, Wiesel received the Nobel Prize in Physiology or Medicine in 1981 along with David Hubel and Roger Sperry. Wiesel determined the critical period during which the visual system of a mammal develops and studied how impairment at that stage of development can cause permanent damage to the neural pathways of the eye, allowing later researchers and surgeons to study the treatment of congenital vision disorders.

In the 1960s in the United States Landrum B. Shettles developed the Shettles method, which is a procedure for couples to use prior to and during an intercourse to increase their chances of conceiving a fetus of their desired sex. Shettles, a physician, who specialized in obstetrics and gynecology, found a difference in the size and shape of male sperm cells that he correlated with the different sex chromosomes they carry. Based on that finding, Shettles developed procedures for couples to follow based on whether they desire a female or a male fetus and published them in the 1970 book, Your Baby’s Sex: Now You Can Choose. The Shettles method is based on the idea that male-producing sperm prefer alkaline conditions, whereas female-producing sperm prefer acidic conditions. The method provides couples with a procedure intended to enhance the favored environment for the sperm that will supposedly produce the desired sex, including female douches to be used before intercourse and how to time sexual intercourse within the female menstrual cycle. The book Your Baby’s Sex: Now You Can Choose, made the Shettles method a widely popular method of natural sex selection.

During 1964, David Hubel and Torsten Wiesel studied the short and long term effects of depriving kittens of vision in one eye. In their experiments, Wiesel and Hubel used kittens as models for human children. Hubel and Wiesel researched whether the impairment of vision in one eye could be repaired or not and whether such impairments would impact vision later on in life. The researchers sewed one eye of a kitten shut for varying periods of time. They found that when vision impairments occurred to the kittens right after birth, their vision was significantly affected later on in life, as the cells that were responsible for processing visual information redistributed to favor the unimpaired eye. Hubel and Wiesel worked together for over twenty years and received the 1981 Nobel Prize for Physiology or Medicine for their research on the critical period for mammalian visual system development. Hubel and Wiesel’s experiments with kittens showed that there is a critical period during which the visual system develops in mammals, and it also showed that any impairment of that system during that time will affect the lifelong vision of a mammal.

David Hunter Hubel studied the development of the visual system and how the brain processes visual information in the US during the twentieth century. He performed multiple experiments with kittens in which he sewed kitten’s eyes shut for varying periods of time and monitored their vision after reopening them. Hubel, along with colleague Torsten Wiesel, received the 1981 Nobel Prize in Physiology or Medicine for that research. By using kittens as models for human children and sewn eyes as models for congenital vision disorders, Hubel’s research demonstrated how vision impairments can affect the development of the visual system in humans. Furthermore, Hubel’s research has informed surgeons about the importance of operating on infants with vision impairments during the first months of life to prevent deterioration of the visual cortex of the brain and permanent vision loss.