Editing Galen (section)

==Medicine==
{{further|Humorism}}
Galen contributed a substantial amount to the understanding of pathology. Under the [[Hippocratic Corpus|Hippocratic]] bodily [[humors]] theory, differences in human moods come as a consequence of imbalances in one of the four [[Body fluid|bodily fluids]]: blood, yellow bile, black bile, and phlegm. Galen promoted this theory and the typology of [[Four temperaments|human temperaments]].<ref name=":02">{{Cite journal|last=Kilgour|first=Frederick G.|date=1957|title=GALEN|url=https://www.jstor.org/stable/24940775 |journal=Scientific American|volume=196|issue=3|pages=105–117 |doi=10.1038/scientificamerican0357-105|jstor=24940775|bibcode=1957SciAm.196c.105K |issn=0036-8733}}</ref> In Galen's view, an imbalance of each humor corresponded with a particular human temperament (blood{{snd}}sanguine, black bile{{snd}}melancholic, yellow bile{{snd}}choleric, and phlegm{{snd}}phlegmatic). Thus, individuals with sanguine temperaments are extroverted and social; choleric people have energy, passion, and charisma; melancholics are creative, kind, and considerate; and phlegmatic temperaments are characterised by dependability, kindness, and affection.<ref name= MarkGrant>{{cite book|first1= Mark|last1=  Grant|date = 2000|title = Galen on Food and Diet|publisher = Psychology Press|isbn = 9780415232333}}</ref>

Galen was also a skilled surgeon, operating on human patients. Many of his procedures and techniques would not be used again for centuries, such as the procedures he performed on brains and eyes.<ref name="Galen on the brain"/> His surgical experiments included ligating the arteries of living animals.<ref>{{cite book|author=Lois N. Magner|title=A History of Medicine|publisher=CRC Press|url  =https://books.google.com/books?id=qtUzscI9_VIC&pg=PA91 |page=91|isbn =9780824786731|year=1992}}</ref> Although many 20th-century historians have claimed that Galen believed the lens to be in the exact center of the eye, Galen actually understood that the crystalline lens is located in the anterior aspect of the human eye.<ref name="Clinical Ophthalmology">{{cite journal|vauthors=Leffler CT, Hadi TM, Udupa A, Schwartz SG, Schwartz D|title=A medieval fallacy: the crystalline lens in the center of the eye|journal=Clinical Ophthalmology|volume=2016|issue=10|pages=649–662|year=2016|pmc=4833360|pmid=27114699|doi=10.2147/OPTH.S100708 |doi-access=free }}</ref>

At first reluctantly but then with increasing vigor, Galen promoted Hippocratic teaching, including [[Venipuncture|venesection]] and [[bloodletting]], then unknown in Rome. This was sharply criticized by the [[Erasistratus|Erasistrateans]], who predicted dire outcomes, believing that it was not blood but ''[[Pneuma (Stoic)|pneuma]]'' that flowed in the veins. Galen, however, staunchly defended venesection in his three books on the subject<ref>Brain P (trans.) Galen on Bloodletting: A study of the origins, development, and validity of his opinions, with a translation of the three works. Cambridge 1986</ref> and in his demonstrations and public disputations. Galen's work on anatomy remained largely unsurpassed and unchallenged up until the 16th century in Europe. In the middle of the 16th century, the anatomist [[Andreas Vesalius]] challenged the anatomical knowledge of Galen by conducting dissections on human cadavers.<ref name="auto"/> These investigations allowed Vesalius to refute aspects of Galen's theories regarding anatomy.

===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.

===Localization of function===
One of Galen's major works, ''On the Doctrines of Hippocrates and Plato'', sought to demonstrate the unity of the two subjects and their views. Using their theories, combined with Aristotle's, Galen developed a tripartite soul consisting of similar aspects.<ref name="gill2007"/><ref name="auto"/> He used the [[Plato's theory of soul|same terms as Plato]], referring to the three parts as rational, spiritual, and appetitive. Each corresponded to a localized area of the body. The rational soul was in the brain, the spiritual soul was in the heart, and the appetitive soul was in the liver. Galen was the first scientist and philosopher to assign specific parts of the soul to locations in the body because of his extensive background in medicine.<ref name= lloyd2007>{{cite journal|author = Lloyd G|year = 2007|title = Pneuma between body and soul|journal = Journal of the Royal Anthropological Institute|volume = 13|pages = S135–S146|doi = 10.1111/j.1467-9655.2007.00409.x}}</ref> This idea is now referred to as localization of function.<ref name=hankinson1991>{{cite journal|author = Hankinson R. J.|year = 1991|title = Galen's anatomy of the soul|journal = Phronesis|volume = 36|issue = 2|pages = 197–233|doi = 10.1163/156852891321052787}}</ref> Galen's assignments were revolutionary for the time period, which set the precedent for future localization theories.

Galen believed each part of this tripartite soul controlled specific functions within the body and that the soul, as a whole, contributed to the health of the body, strengthening the "natural functioning capacity of the organ or organs in question".<ref name="hankinson1991"/><ref name="auto"/> The rational soul controlled higher level cognitive functioning in an organism, for example, making choices or perceiving the world and sending those signals to the brain.<ref name="hankinson1991"/> He also listed "imagination, memory, recollection, knowledge, thought, consideration, voluntary motion, and sensation" as being found within the rational soul.<ref name="hankinson1991"/> The functions of "growing or being alive" resided in the spirited soul.<ref name="hankinson1991"/> The spirited soul also contained our passions, such as anger. These passions were considered to be even stronger than regular emotions, and, as a consequence, more dangerous.<ref name="hankinson1991"/> The third part of the soul, or the appetitive spirit, controlled the living forces in our body, most importantly blood.<ref name="hankinson1991"/> The appetitive spirit also regulated the pleasures of the body and was moved by feelings of enjoyment. This third part of the soul is the animalistic, or more natural, side of the soul; it deals with the natural urges of the body and survival instincts. Galen proposed that when the soul is moved by too much enjoyment, it reaches states of "incontinence" and "licentiousness", the inability to willfully cease enjoyment, which was a negative consequence of too much pleasure.<ref name="hankinson1991"/>

In order to unite his theories about the soul and how it operated within the body, he adapted the theory of the ''pneuma'',<ref name="lloyd2007"/> which he used to explain how the soul operated within its assigned organs, and how those organs, in turn, interacted together. Galen then distinguished the vital ''pneuma'', in the arterial system, from the psychic ''pneuma'', in the brain and nervous system.<ref name="lloyd2007"/> Galen placed the vital ''pneuma'' in the heart and the psychic ''pneuma'' (''spiritus animalis'') within the brain.<ref>{{cite book|author=Dennis Sepper|editor-first1=Lawrence |editor-last1=Nolan |url=https://www.cambridge.org/core/books/abs/cambridge-descartes-lexicon/animal-spirits/C857021D22C021EF7129A2D450740D98|title=The Cambridge Descartes Lexicon|chapter=Animal Spirits |year=2015 |pages=26–28 |publisher=Cambridge University Press |doi=10.1017/CBO9780511894695.011 |isbn=9780521193528 }}</ref> He conducted many anatomical studies on animals, most famously an ox, to study the transition from vital to psychic ''pneuma''.<ref name="lloyd2007"/> Although highly criticized for comparing animal anatomy to human anatomy, Galen was convinced that his knowledge was abundant enough in both anatomies to base one on the other.<ref name="lloyd2007"/>
In his treatise ''On the usefulness of the parts of the body'', Galen argued that the perfect suitability of each part of the body to its function indicated the role of an intelligent creator.<ref>{{cite web|url=http://www.topoi.org/project/plus-7/|title =Mapping the Soul in the Instrumental Body: Galen on the Functions of the Parts of the Human Body}}</ref> His [[Creationism#Theistic evolution|creationism]] was anticipated by the anatomical examples of [[Socrates]] and [[Empedocles]].<ref>{{cite book|author=[[David Sedley]]|url=https://www.christs.cam.ac.uk/socrates-vs-darwin|title=Socrates vs Darwin|publisher=[[Christ's College, Cambridge]]}}</ref>