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Penile subincision is a form of body modification consisting of a urethrotomy, in which the underside of the penis is incised and the urethra slit open lengthwise, from the urethral opening (meatus) toward the base. The slit can be of varying lengths.
Subincision is traditionally performed around the world, notably in Australia, but also in Africa, South America and the Polynesian and Melanesian cultures of the Pacific, often as a coming of age ritual.
Disadvantages include the risk of surgery, which is often self-performed, and increased susceptibility to sexually transmitted infections (STIs). The ability to impregnate (specifically, getting sperm into the vagina) may also be decreased.
Subincisions can greatly affect urination and often require the subincised male to sit or squat while urinating. The scrotum can be pulled up against the open urethra to quasi-complete the tube and allow an approximation to normal urination, while a few subincised men carry a tube with which they can aim.
Subincision (like circumcision) is widespread in the traditional cultures of Indigenous Australians, and is well documented among the peoples of the central desert of Australia such as the Arrernte and Luritja. The Arrernte word for subincision is arilta, and occurs as a rite of passage ritual for adolescent boys. It was given to the Arrernte by Mangar-kunjer-kunja, a lizard-man spirit being from the Dreamtime. A subincised penis is thought to resemble a vulva, and the bleeding is likened to menstruation. This type of modification of the penis was also traditionally performed by the Lardil people of Mornington Island, Queensland. The young men who chose to endure this custom were the only ones to learn a simple ceremonial language, Damin. In later ceremonies, repeated throughout adult life, the subincised penis would be used as a site for ritual bloodletting. According to Ken Hale, who studied Damin, no ritual initiations have been carried out in the Gulf of Carpentaria for half a century, and hence the language has also died out.
Another indigenous Australian term for the custom is mika or the terrible rite.
Indigenous cultures of the Amazon Basin also practise subincision, as do Samburu herdboys of Kenya, who are said to perform subincisions on themselves (or sometimes their peers) at age seven to ten. In Samoa, subincision of the foreskin, skin located along the tip of the penis, was ritually performed upon young men, as in Hawaii, where subincision of the foreskin is reported to have been performed at age six or seven.
A subincized penis can be penetrated by another penis, provided the latter is sufficiently small. In some Australian cultures, one traditional practice involved the penetration of an elder's subincized penis by the unsubincized penis of a young boy who was usually under age 7. Some authors have theorized that this was the original purpose of subincision. 
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