Semen, ejaculate or cum (a corruption of come) is the fluid discharged from the penis during ejaculation, usually at the time of orgasm. Like blood, semen consists of two components, cellular (spermatozoa and incidental cells, generally including some immune system cells) and noncellular compartment (seminal plasma). It contains the sperm, which sometimes results in pregnancy following vaginal sex with a female. Semen is a whitish, milky fluid, slightly viscous, containing water and small amounts of salts, protein, and fructose.
Semen and transmission of disease
Semen is in itself harmless on the skin or if swallowed. However, semen can be the vehicle for some sexually transmitted diseases, including HIV, the virus that causes AIDS. It is also hypothesized that components of semen, such as the spermatozoa as well as the seminal plasma, can cause immunosuppression in the body when introduced to the bloodstream or lymph. Evidence for this dates back to 1898, when Elie Metchnikoff injected a guinea pig with its own and foreign guinea pig sperm, finding that an antibody was produced in response; however the antibody was inactive, pointing to a suppression response by the immune system. Further research, such as that by S. Mathur and J.M. Goust, demonstrated that non-preexisting antibodies were produced in humans in response to one's own sperm. These antibodies mistakenly recognized native T lymphocytes as foreign antigens, and consequently the T lymphyocytes would fall under attack by the body's B lymphocytes.
Other semen components shown to spur an immunosuppressive effect are seminal plasma and seminal lymphocytes.
Note that any kind of sexual or other skin contact with the semen of a person infected with HIV should be avoided, even by persons already infected with the virus, as this may cause re-infection by a different strain.
In some cultures, semen is attributed with special properties of masculinity. For instance, among the Etoro people of Papua New Guinea, it is believed that young boys must fellate their elders and ingest their sperm to achieve proper sexual maturation. Other cultures believe semen to have beneficial qualities when applied to the skin, mainly for cosmetic purposes.
- Mann T, Lutwak-Mann C. 1981. Male Reproductive Function and Semen. Berlin: Springer-Verlag. ISBN 3-540-10383, 0-387-10383.
- Shivaji S, Scheit K-H, Bhargava PM. 1990. Proteins of seminal plasma. New York: John Wiley & Sons. ISBN 0-471-84685-6.