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Dissection (also called anatomization) is the process of disassembling and observing something to determine its internal structure and as an aid to discerning the functions and relationships of its components.
Dissection is usually applied to the examination of plants and animals. The term is also used in relation to mechanisms, computer programs, written materials, etc., as a synonym for terms such as reverse engineering or literary deconstruction. Dissection is usually performed by students in courses of biology, botany and anatomy and in association with medical and arts studies.
Vivisection refers to the dissection of a living animal, often for the purposes of physiological investigation and nowadays usually under heavy sedation. However, the term is no longer widely used, in part because more sophisticated techniques have superseded it for many applications. The term is now almost entirely used in a pejorative sense by those who oppose animal testing of any sort.
Dissection is often performed as a part of determining a cause of death in autopsy (on humans) and necropsy (on animals) and is an intrinsic part of forensic medicine, such as would be practiced by a coroner.
Human dissections were carried out by the Greek physicians Herophilus of Chalcedon and Erasistratus of Chios in the early part of the third century BC. Before and after this time investigators appeared to largely limit themselves to animals. Roman law forbade dissection and autopsy of the human body, so physicians such as Galen were unable to work on cadavers. Galen for example dissected the Barbary Macaque and other primates, assuming their anatomy was basically the same as that of humans.
It is not known whether or not human dissections were also conducted by Arabic physicians. Islamic scholars such as Al-Ghazali expressed support for its practice. It is possible that Islamic physicians may have performed dissections, including Ibn Zuhr (Avenzoar) (1091–1161) in Al-Andalus,[unreliable source?] Saladin's physician Ibn Jumay during the 12th century, Abd el-Latif in Egypt c. 1200, and Ibn al-Nafis in Syria and Egypt in the 13th century. However, doubt remains because al-Nafis, a specialist in Islamic jurisprudence, construed dissection as un-Islamic and avoided it, citing "shari'a [the religious law] and his own 'compassion' for the human body".
Unlike pagan Rome, Christian Europe did not exercise a universal prohibition of the dissection and autopsy of the human body and such examinations were carried out regularly from at least the 13th century. It has even been suggested that Christian theology contributed significantly to the revival of human dissection and autopsy by providing a new socio-religious and cultural context in which the human cadaver was no longer seen as sacrosanct.
Throughout history, the dissection of human cadavers for medical education has experienced various cycles of legalization and proscription in different countries. Anatomization has even been ordered as a form of punishment (as, for example, in 1805 at Massachusetts to James Halligan and Dominic Daley after their public hanging). An edict of the 1163 Council of Tours, and an early 14th century decree of Pope Boniface VIII have mistakenly been identified as prohibiting dissection and autopsy, but no universal prohibition of dissection or autopsy was exercised during the Middle Ages. Rather, the era witnessed the revival of an interest in medical studies, and a renewal in human dissection and autopsy. Some European countries began legalizing the dissection of executed criminals for educational purposes in the late 13th and early 14th centuries, and Mondino de Liuzzi carried out the first recorded public dissection around 1315. Vesalius in the 16th century carried out numerous dissections in the process of performing some of the most extensive anatomical investigations up to his time, but was attacked frequently by other physicians for his disagreement with Galen's studies of human anatomy. For many years it was assumed that Vesalius's pilgrimage to Palestine was an escape from pressures of the Inquisition brought as a result of his work with cadavers. Today this is generally considered to be without foundation and is dismissed by modern biographers.
The Catholic church is known to have ordered an autopsy on conjoined twins Joana and Melchiora Ballestero in Hispanola in 1533 to determine whether they shared a soul. They found that there were two distinct hearts, and hence two souls, based on the ancient Greek philosopher Empedocles, who believed the soul resided in the heart.
In England, dissection remained entirely prohibited until the 16th century, when a series of royal edicts gave specific groups of physicians and surgeons some limited rights to dissect cadavers. The permission was quite limited: by the mid-18th century, the Royal College of Physicians and Company of Barber-Surgeons were the only two groups permitted to carry out dissections, and had an annual quota of ten cadavers between them. As a result of pressure from anatomists, especially in the rapidly growing medical schools, the Murder Act 1752 allowed the bodies of executed murderers to be dissected for anatomical research and education. By the 19th century this supply of cadavers proved insufficient, however, due to both the continuing expansion of medical schools, and the creation of a number of private medical schools, which lacked legal access to cadavers. A thriving black market arose in cadavers and body parts, leading to the creation of an entire profession of body-snatcher, and even more extremely, the infamous Burke and Hare murders in 1828, when 16 people were murdered in order to sell their cadavers to anatomists. The resulting public outcry largely led to the passage of the Anatomy Act 1832, which greatly increased the legal supply of cadavers for dissection. (See also: History of anatomy in the 19th century.)
By the 21st century, the availability of interactive computer programs and changing public sentiment led to renewed debate on the use of cadavers in medical education. The Peninsula College of Medicine and Dentistry in the UK, founded in 2000, became the first modern medical school to carry out its anatomy education without dissection, though most medical schools continue to see experience with actual cadavers as preferable to entirely computer-based education.
Dissections of non-human animals have also been used for educational purposes, often in general science education where the use of human cadavers would not be justified. In the United States, dissection of frogs became common in college biology classes from the 1920s, and gradually began to be introduced at earlier stages of education. By 1988 an estimated 75 to 80 percent of American high school biology students were participating in a frog dissection, with a trend towards introduction in elementary schools. The dissected frogs are most commonly from the Rana genus. Other popular animals for high-school dissection at the time of that survey were, among vertebrates, fetal pigs, perch, and cats; and among invertebrates, earthworms, grasshoppers, crayfish, and starfish.
Controversy over dissection in U.S. high schools became prominent in 1987, when a California student, Jenifer Graham, sued to require her school to let her complete an alternate project. The court ruled that mandatory dissections were permissible, but that Graham could ask to dissect a frog that had died of natural causes rather than one that was killed for the purposes of dissection; the practical impossibility of procuring a frog that had died of natural causes in effect let Graham opt out of the required dissection. The suit also gave considerable publicity to anti-dissection advocates. Graham appeared in a 1987 Apple Computer commercial for the virtual-dissection software Operation Frog. The state of California passed a Student's Rights Bill in 1988 requiring that objecting students be allowed to complete alternative projects. The trend towards students opting out of dissection increased through the 1990s.
The following are tools commonly used in biological dissection.
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