Editing Galen (section)

===Anatomy===
[[File:Galen's "Physiological system" Wellcome M0000376.jpg|thumb|upright=.9|An interpretation of Galen's human "physiological system"]]

Galen's interest in human anatomy ran afoul of Roman law that prohibited the dissection of human cadavers since roughly 150 BC.<ref>'Tragically, the prohibition of human dissection by Rome in 150 BC arrested this progress and few of their findings survived', Arthur Aufderheide, 'The Scientific Study of Mummies' (2003), p. 5</ref> Because of this restriction, Galen performed anatomical dissections on living ([[vivisection]]) and dead animals, mostly focusing on [[primate]]s.<ref name="brock"/> Galen believed that the anatomical structures of these animals closely mirrored those of humans. Galen clarified the anatomy of the [[trachea]] and was the first to demonstrate that the [[larynx]] generates the voice.<ref>{{cite book|author=Claudii Galeni Pergameni|title=Galen on anatomical procedures: De anatomicis administrationibus|editor=translated by [[Charles Singer|Charles Joseph Singer]]|publisher=Geoffrey Cumberlege, Oxford University Press/Wellcome Historical Medical Museum|location=London|year=1956|pages=195–207}}</ref><ref>{{cite journal|author=Claudii Galeni Pergameni|title=Galen on Anatomical Procedures|journal=Proceedings of the Royal Society of Medicine|volume=49|issue=10|pages=833|date=October 1956|doi=10.1177/003591575604901017|pmc=1889206}}</ref> In one experiment, Galen used bellows to inflate the lungs of a dead animal.<ref>{{cite book|author=Claudii Galeni Pergameni
|title=De usu partium corporis humani, libri VII|editor=Nicolao Regio Calabro (Nicolaus Rheginus)|chapter=De usu partium corporis humani, libri VII, cap. IV|publisher=ex officina Simonis Colinaei|location=[[Paris]]|language=la|year=1528|pages=339
|chapter-url=http://gallica.bnf.fr/ark:/12148/bpt6k542146.image.f8|access-date=7 August 2010}}</ref><ref name=Baker1971>{{cite journal
|author=A. Barrington Baker|title=Artificial respiration, the history of an idea|journal=Medical History|volume=15|issue=4
|pages=336–351|date=October 1971|pmid=4944603|pmc=1034194|doi=10.1017/s0025727300016896}}</ref> Galen's research on [[physiology]] was largely influenced by previous works of philosophers Plato and Aristotle, as well as from the physician Hippocrates. He was one of the first people to use experiments as a method of research for his medical findings.<ref>{{Cite web|title=BBC – History – Historic Figures: Galen (c. 130 – c. 210)|url=http://www.bbc.co.uk/history/historic_figures/galen.shtml|access-date=18 December 2020|website=www.bbc.co.uk|language=en-GB}}</ref> Doing so allowed him to explore various parts of the body and its functions.

Among Galen's major contributions to medicine was his work on the [[circulatory system]]. He was the first to recognize that there are distinct differences between [[venous blood|venous]] (dark) and [[arterial blood|arterial]] (bright) blood. In addition to these discoveries, Galen postulated much more about the nature of the [[circulatory system]]. He believed that blood originated in the liver, which follows the teachings of Hippocrates. The liver converted nutrients gathered from ingested food into blood to be used in the circulatory system.<ref name=":1">{{Cite journal|last=Aird|first=W. C.|date=July 2011|title=Discovery of the cardiovascular system: from Galen to William Harvey: Discovery of the cardiovascular system|journal=Journal of Thrombosis and Haemostasis|language=en|volume=9|pages=118–129|doi=10.1111/j.1538-7836.2011.04312.x|pmid=21781247|s2cid=12092592|doi-access=free}}</ref> The blood created in the liver would eventually flow unidirectionally into the right ventricle of the heart via the great vein.<ref name=":1"/> Galen also proposed a theory on how blood receives air from the lungs to be distributed throughout the body. He declared that the venous artery carried air from the lungs into the left ventricle of the heart to mix with created blood from the liver.<ref name=":1"/> This same venous artery allowed for an exchange of waste products from the blood back into the lungs to be exhaled.<ref name=":1"/> In order to receive air from the lungs in the left ventricle, the new blood needed to get there from the right ventricle. Thus, Galen asserted that there are small holes in the septum dividing the left and right sides of the heart; these holes allowed the blood to pass through easily to receive air and exchange the aforementioned waste products.<ref>{{Cite journal|last=Kuusela|first=P. J.|date=2014|title=The heart exhibits right to left communication between the fibres of the muscular part of the interventricular septum|url=https://journals.viamedica.pl/folia_morphologica/article/view/FM.2014.0006|journal=Folia Morphologica|language=en|volume=73|issue=1|pages=42–50|doi=10.5603/FM.2014.0006|pmid=24590522|issn=1644-3284|doi-access=free}}</ref> Although his anatomical experiments on animal models led him to a more complete understanding of the circulatory system, [[nervous system]], [[respiratory system]], and other structures, his work contained scientific errors.<ref name="Galen on the brain"/> Galen believed the circulatory system to consist of two separate one-way systems of distribution, rather than a single unified system of circulation. He believed venous blood to be generated in the liver, from where it was distributed and consumed by all organs of the body. He posited that arterial blood originated in the heart, from where it was distributed and consumed by all organs of the body. The blood was then regenerated in either the liver or the heart, completing the cycle. Galen also believed in the existence of a group of blood vessels he called the [[rete mirabile]] in the carotid sinus.<ref name="MarkGrant"/> Both of these theories of the circulation of blood were later (beginning with works of [[Ibn al-Nafis]] published {{Circa|1242|lk=no}}) shown to be incorrect.<ref name="Furley1984">Furley, D, and J. Wilkie, 1984, ''Galen On Respiration and the Arteries'', Princeton University Press, and Bylebyl, J (ed), 1979, ''William Harvey and His Age'', Baltimore: Johns Hopkins University Press</ref>

Galen was also a pioneer in research about the human spine. His dissections and vivisections of animals led to key observations that helped him accurately describe the human spine, [[spinal cord]], and [[vertebral column]]. Galen also played a major role in the discoveries of the [[central nervous system]]. He was also able to describe the nerves that emerge from the spine, which is integral to his research about the nervous system.<ref>{{Cite journal|last=Pasipoularides|first=Ares|title=Galen, father of systematic medicine. An essay on the evolution of modern medicine and cardiology|journal=International Journal of Cardiology|year=2014|volume=172|issue=1|pages=47–58|doi=10.1016/j.ijcard.2013.12.166|pmid=24461486}}</ref> Galen went on to be the first physician to study what happens when the spinal cord is transected on multiple different levels.<ref>{{Cite news|title=Galen: A Pioneer of Spine Research : Spine|language=en-US|work=LWW|url=https://journals.lww.com/spinejournal/Abstract/1999/11150/Galen__A_Pioneer_of_Spine_Research.12.aspx|access-date=18 December 2020}}</ref> He worked with pigs and studied their [[neuroanatomy]] by severing different nerves either totally or partially to see how it affected the body. He even dealt with diseases affecting the spinal cord and nerves. In his work ''De motu musculorum'', Galen explained the difference between [[motor nerve|motor]] and [[sensory nerve]]s, discussed the concept of [[muscle tone]], and explained the difference between [[agonist (muscle)|agonists]] and [[antagonist (muscle)|antagonists]].

Galen's work on animals led to some inaccuracies, most notably his anatomy of the uterus which largely resembled a dog's. Though incorrect in his studies of human reproduction and reproductive anatomy, he came very close to identifying the ovaries as analogous to the male testes. [[Reproduction]] was a controversial topic in Galen's lifetime, as there was much debate over if the male was solely responsible for the seed, or if the woman was also responsible.

Through his vivisection practices, Galen also proved that the voice was controlled by the brain. One of the most famous experiments that he recreated in public was the squealing pig: Galen would cut open a pig, and while it was squealing he would tie off the recurrent laryngeal nerve, or vocal cords, showing they controlled the making of sound. He used the same method to tie off the ureters to prove his theories of kidney and bladder function. Galen believed the human body had three interconnected systems that allowed it to work. The first system that he theorized consisted of the brain and the nerves, responsible for thought and sensation. The second theorized system was the heart and the arteries, which Galen believed to be responsible for providing life-giving energy. The last theorized system was the liver and veins, which Galen theorized were responsible for nutrition and growth. Galen also theorized that blood was made in the liver and sent out around the body.