Semen

Depending on the species, spermatozoa can fertilize ova externally or internally. In external fertilization, the spermatozoa fertilize the ova directly, outside of the female's sexual organs. Female fish, for example, spawn ova into their aquatic environment, where they are fertilized by the semen of the male fish.

Internal fertilization occurs inside the female's sexual organs after a male inseminates a female through copulation. Most vertebrates, including amphibians, reptiles, birds and monotreme mammals, are inseminated through the cloaca.^[1]Marsupials and placental mammals are inseminated through the vagina.^[2][3] In macropods, semen coagulates and forms a mating plug in the vagina after copulation.^[2][4]

Semen quality is a measure of the ability of semen to accomplish fertilization. Thus, it is a measure of fertility in a man. It is the sperm in the semen that is the fertile component, and therefore semen quality involves both sperm quantity and sperm quality.^[16]

The volume of semen ejaculate varies but is generally about 1 teaspoonful or less. A review of 30 studies concluded that the average was around 3.4 milliliters (mL), with some studies finding amounts as high as 5.0 mL or as low as 2.3 mL.^[10] In a study with Swedish and Danish men, a prolonged interval between ejaculations caused an increase in the sperm count in the semen but not an increase in the semen volume.^[17]

Semen can be stored in diluents such as the Illini Variable Temperature (IVT) diluent, which have been reported to be able to preserve high fertility of semen for over seven days.^[18] The IVT diluent is composed of several salts, sugars and antibacterial agents and gassed with CO₂.^[18]

Semen cryopreservation can be used for far longer storage durations. For human sperm, the longest reported successful storage with this method is 21 years.^[19]

Semen can transmit many sexually transmitted infections and pathogens, including viruses like HIV^[20] and Ebola.^[21] Swallowing semen carries no additional risk other than those inherent in fellatio. This includes transmission risk for sexually transmitted infections such as human papillomavirus or herpes, especially for people with bleeding gums, gingivitis or open sores.^[22][23] Viruses in semen survive for a long time once outside the body.^[24][25][26]

The presence of blood in semen or hematospermia may be undetectable (it can only be seen microscopically) or visible in the fluid. Its cause could be the result of inflammation, infection, blockage, or injury of the male reproductive tract or a problem within the urethra, testicles, epididymis or prostate. It usually clears up without treatment, or with antibiotics, but if persistent further semen analysis and other urogenital system tests might be needed to find out the cause.

In rare circumstances, humans can develop an allergy to semen, called human seminal plasma sensitivity. It appears as a typical localized or systemic allergic response upon contact with seminal fluid. There is no one protein in semen responsible for the reaction. Symptoms can appear after first intercourse or after subsequent intercourse. A semen allergy can be distinguished from a latex allergy by determining if the symptoms disappear with use of a condom. Desensitization treatments are often very successful.^[27][28]

Among numerous species in the animal kingdom, females may benefit from absorbing nutrients and proteins from seminal fluid for food, antiviral and antibacterial properties, and enhanced fertilisation. In humans, seminal fluid provides anti-viral activity towards herpes simplex virus and can transfer anti-microbial peptides cathelicidin and lactoferrin. In birds and mammals, mutualistic bacteria such as Lactobacillus have been detected in fluid transferral.^[20]

A study on the effect of semen in male-to-female transmission of HIV, in both humans and non-human primates (rhesus macaques), noted that regular intravaginal exposure to a healthy male's semen modulates the microenvironment in the female reproductive tract (FRT), and, paradoxically, improves the resistance in females against acquiring HIV by activating their bodies' anti-HIV mechanisms.^[29]

Qigong and Chinese medicine place huge emphasis on a form of energy called 精 (pinyin: jīng, also a morpheme denoting "essence" or "spirit")^[30][31] – which one attempts to develop and accumulate. "Jing" is sexual energy and is considered to dissipate with ejaculation, so masturbation is considered "energy suicide" amongst those who practice this art. According to Qigong theory, energy from many pathways/meridians becomes diverted and transfers itself to the sexual organs during sexual excitement. The ensuing orgasm and ejaculation will then finally expel the energy from the system completely. The Chinese proverb 一滴精，十滴血 (pinyin: yì dī jīng, shí dī xuè, literally: a drop of semen is equal to ten drops of blood) illustrates this point.

The scientific term for semen in Chinese is 精液 (pinyin: jīng yè, literally: fluid of essence/jing) and the term for sperm is 精子 (pinyin: jīng zǐ, literally: basic element of essence/jing), two modern terms with classical referents.

The Upanishads, principal scriptures of Hinduism, propound a creation theory wherein the supreme self transmutes itself to become the creation by exerting tremendous effort and strenuous labor (śrama), which is enabled on by tapas or "heat", considered as the most important element in the entire creation process.^[32] The word tapas, in Sanskrit literature, is understood as a reference to the sexual heat or warmth that incubates the birth of life.^[33] The root word tapas was commonly used for descriptions of sexual desire and love.^[34] The word kama (desire) was homologized with tapas (heat) to explain the emotions and energy that leads to intercourse.^[35][36]

The connection between bodily heat (tapas) and sexual desire (kama) is not just metaphorical but is found to be rooted in physiology, "All adolescent and fertile adults are hot."^[37]:126 The internal bodily heat, apart from being present inherently in certain body types (thinness more heat), is generated by processes such as "menstruation, childbirth, consumption of hot food, sexual desire" and certain emotions like anger and jealousy.^[37]:126 While heat is regarded as necessary to sustain life, with complete coldness corresponding to death, excessive bodily heat is "undesirable and dangerous" as it causes the body to deteriorate by internal consumption. A state of "relative coolness" is considered ideal.^[37]:126

Women, in general, are deemed as relatively hotter than men, partly due to menstruation and pregnancies, which result in higher concentrations of blood to the womb. Menstruation, in particular is considered as extremely heating, a process likened to "boiling over" and is sought to be alleviated by acts such as menstrual seclusion, and oiling-bathing of the menstruating women, apart from rituals.^[37]:126 In the Indian state of Kerala, a ritual conducted for virgin girls was talikettukalyanam, in which the girls are wedded to a boy or a man in a mock-marriage and after consummating are separated without any claims on each other.^[37]:127 In sexually matured females, menstruation and unfulfilled sexual desire is believed to boil over their blood, with the heat making them violent and maniacal unless they are regularly cooled down by man's semen, which, is considered to be an extremely cooling substance.^[37]:127 Though excessive heat in a woman is synonymous with "shakti and latent fertility", it is potentially dangerous and must be restrained, lessened and transmuted. This is sought to be achieved by "binding", wherein women wear tight upper clothing, bangles and necklaces; and "sealing the body" in oil baths and herbal powders; and through regular sexual intercourse. A woman is said to be really cool only after childbirth and had breast-feed her baby.^[37]:126

Men, too, overheat in absence of regular ejaculation and can become a danger.^[37]:127 In men, the semen heats up gradually and, if not ejaculated, should be channelled through the kundalini by means of demanding yogic practices.^[37]:127 Hindu men have an ascetic–erotic conundrum as they believe abstinence yields power, as well as in satisfying their desires as a necessity.^[37]:115Morris Carstairs, in a report on culture and personality study, stated that Indian men who are seemingly healthy are preoccupied with real or imagined spermatorrhea, with the belief that semen is not easily formed and "it takes 40 days, and 40 drops of blood, to make one drop of semen". He observed that when sexual behaviours are restricted, sexual incontinence follows with resultant guilt.^[37]:115 In females, the corresponding fear of loss of sexual fluids is found in anxieties over vaginal discharge (sravam), which is believed to be a cooling body lubricant but whose loss leaves them "overheated and disarticulated, in a state of disease."^{[37]:117–118} Anxiety about loss of sexual fluids is caused from a misdiagnosis of sexual guilt, instead of correcting the psyche of a person the focus is shifted onto the substance (semen, sravam), resulting in subsequent pathologization.^:115[37]

In Ayurveda, the term generally used for both male semen and female egg cell is Shukra. People with healthy shukra appear stronger and confident, with eyes and skin that seem lustrous. Those who lack higher shukra appear exhausted and lackluster, while also struggling in creative endeavours. Drinking lots of water and proper digestion of highly nourishing foods (milk, ghee, nuts) yield healthy shukra.^[38]Charaka states brahmacharya (abstinence), proper diet, and rest/sleep as the three pillars of life. Indulgence in sexual activity is healthy for stronger individuals, but in weaker people it weakens them further, and is sought to be alleviated by abstinence as it restores shukra, which is always produced as a result of the digestion of food one eats.^[38] Ayurveda makes no preference for a celibate or monastic lifestyle, nor does it stress on morality being a part of human sexuality. The health of an individual's shukra and their dharma decides the degree of their sexual activity; for a householder sexual expression is common, while it is not so for a renunciate monk.^[38]

In Ancient Greece, Aristotle remarked on the importance of semen: "For Aristotle, semen is the residue derived from nourishment, that is of blood, that has been highly concocted to the optimum temperature and substance. This can only be emitted by the male as only the male, by nature of his very being, has the requisite heat to concoct blood into semen."^[39] According to Aristotle, there is a direct connection between food and semen: "Sperms are the excretion of our food, or to put it more clearly, as the most perfect component of our food."^[40]

The connection between food and physical growth, on the one hand, and semen, on the other, allows Aristotle to warn against "engag[ing] in sexual activity at too early an age ... [since] this will affect the growth of their bodies. Nourishment that would otherwise make the body grow is diverted to the production of semen. Aristotle is saying that at this stage the body is still growing; it is best for sexual activity to begin when its growth is 'no longer abundant', for when the body is more or less at full height, the transformation of nourishment into semen does not drain the body of needed material."^[41]

Additionally, "Aristotle tells us that the region round the eyes was the region of the head most fruitful of seed ("most seedy" σπερματικώτατος), pointing to generally recognised effects upon the eyes of sexual indulgence and to practices which imply that seed comes from liquid in the region of the eyes."^[42] This may be explained by the belief of the Pythagoreans that "semen is a drop of the brain [τὸ δε σπέρμα εἶναι σταγόνα ἐγκέφαλου]."^[43]

Greek Stoic philosophy conceived of the Logos spermatikos ("seminal word") as the principle of active reason that fecundated passive matter.^[44] The Jewish philosopher Philo similarly spoke in sexual terms of the Logos as the masculine principle of reason that sowed seeds of virtue in the feminine soul.^[45]

The Christian Platonist Clement of Alexandria likened the Logos to physical blood^[46] as the "substance of the soul",^[47] and noted that some held "that the animal semen is substantially foam of its blood".^[48] Clement reflected an early Christian view that "the seed ought not be wasted nor scattered thoughtlessly nor sown in a way it cannot grow."^[49]

Women were believed to have their own version, which was stored in the womb and released during climax. Retention was believed to cause female hysteria.^[50]

In ancient Greek religion as a whole, semen is considered a form of miasma, and ritual purification was to be practised after its discharge.^[51]

In some pre-industrial societies, semen and other body fluids were revered because they were believed to be magical. Blood is an example of such a fluid, but semen was also widely believed to be of supernatural origin and effect and was, as a result, considered holy or sacred. The ancient Sumerians believed that semen was "a divine substance, endowed on humanity by Enki", the god of water.^[52]:28[53] The semen of a god was believed to have magical generative powers.^[52]:49 In Sumerian mythology, when Enki's seed was planted in the ground, it caused the spontaneous growth of eight previously nonexistent plants.^[52]:49[54] Enki was believed to have created the Tigris and Euphrates rivers by masturbating and ejaculating into their empty riverbeds.^[52]:32,49 The Sumerians believed that rain was the semen of the sky-god An,^[55] which fell from the heavens to inseminate his consort, the earth-goddess Ki,^[55] causing her to give birth to all the plants of the earth.^[55]

The orchid's twin bulbs were thought to resemble the testicles, which is the etymology of the disease orchiditis. There was an ancient Roman belief that the flower sprang from the spilled semen of copulating satyrs.^[56]

In a number of mythologies around the world, semen is often considered analogous to breast milk. In the traditions of Bali, it is considered to be the returning or refunding of the milk of the mother in an alimentary metaphor. The wife feeds her husband who returns to her his semen, the milk of human kindness.^[57]

Nancy Friday's book, Men in Love – Men's Sexual Fantasies: The Triumph of Love over Rage (1982), suggests that swallowing semen is high on a man's intimacy scale.^[58]

When the British Secret Intelligence Service discovered that semen made a good invisible ink, Sir Mansfield George Smith-Cumming noted of his agents that "Every man (is) his own stylo".^[59]

Ingestion of semen offers nominal nutritional value, but has been recorded for social and interpersonal purposes, with some religious or cultural traditions, incorporating it as a practice. It is a common element of oral sex in sexual relationships, and is a common act in pornography, with a number of different kinds of practices depicted.

A huge variety of euphemisms and dysphemisms have been invented to describe semen .

Slang terms for semen include cum, jism (also shortened to jizz), spunk (primarily British English), spooge, splooge, load, nut, seed, and love juice.^[60][61] The term cum can also refer to an orgasm (when used as a verb rather than as a noun). The term nut originally referred to a testicle, but can be used to refer to both semen and ejaculation.