Editing Purr (section)

==Mechanism==
The mechanism by which cats purr is an object of speculation, with different hypotheses proposed. An early idea was that purring is a hemodynamic process where sound is produced as the blood runs through the thorax.<ref>{{Cite journal|title=Melody matters: An acoustic study of domestic cat meows in six contexts and four mental states|last1=Schötz|first1=Susanne|last2=van de Weijer|first2=Joost|date=2019-08-29|last3=Eklund|first3=Robert|doi = 10.7287/peerj.preprints.27926v1|doi-access=free}}</ref>

There is a unique "[[Neural oscillation|neural oscillator]]" in the cat's brain of uncertain significance.<ref name="CPEM">{{cite web | url = https://www.loc.gov/rr/scitech/mysteries/catspurr.html | title = Why and how do cats purr? | access-date = 2011-04-10 | publisher = [[Library of Congress]]}}</ref> Although the mechanism has not yet been fully explained, recent studies have inferred it could be the result of oscillatory mechanisms in the central nervous system.<ref>{{Cite journal|last1=Remmers|first1=J. E.|last2=Gautier|first2=H.|date=1972-12-01|title=Neural and mechanical mechanisms of feline purring|journal=Respiration Physiology|volume=16|issue=3|pages=351–361|doi=10.1016/0034-5687(72)90064-3|pmid=4644061|issn=0034-5687}}</ref>  Studies have also shown that purring can be caused through electrically stimulating the infundibular region of the cat's brain, suggesting central control.<ref>{{Cite journal|last1=Gibbs|first1=E. L.|last2=Gibbs|first2=F. A.|date=1936|title=A purring center in the cat's brain|journal=Journal of Comparative Neurology|language=en|volume=64|issue=2|pages=209–211|doi=10.1002/cne.900640203|s2cid=84375344|issn=1096-9861}}</ref>

===Vocal folds/laryngeal muscles===
One hypothesis, backed by [[electromyographic]] studies, is that cats produce the purring noise by using the [[vocal folds]] or the muscles of the [[larynx]] to alternately dilate and constrict the [[glottis]] rapidly, causing air vibrations during inhalation and exhalation.<ref>K.M. Dyce, W.O. Sack and C.J.G. Wensing in ''Textbook of Veterinary Anatomy 3rd Ed.'' '''2002''', Saunders, Philadelphia; p156</ref> Combined with the steady inhalation and exhalation of air as the cat breathes, a purring noise is produced with strong [[harmonics]].<ref>{{cite web|url=http://www.sccgov.org/sites/parks/For%20Kids%20Here/Pages/How-A-Puma-Purrs.aspx|title=How A Puma Purrs|url-status=dead|archive-url=https://web.archive.org/web/20130122190014/http://www.sccgov.org/sites/parks/For%20Kids%20Here/Pages/How-A-Puma-Purrs.aspx|archive-date=2013-01-22}}</ref>

===Degree of hyoid ossification===
No cat can both purr and [[roar (vocalization)|roar]]. The subdivision of the Felidae into "purring cats" ([[Felinae]]) on one hand and "roaring cats" ([[Pantherinae]]) on the other goes back to Owen<ref>{{cite journal|doi=10.1111/j.1096-3642.1835.tb00611.x|title=On the Anatomy of the Cheetah, Felis jubata, Schreb|journal=The Transactions of the Zoological Society of London|volume=1|issue=2|pages=129–136|year=1834|last1=Owen|first1=Richard}}</ref> and was definitively introduced by Pocock,<ref>{{cite journal|doi=10.1080/00222931608693839|title=On the hyoidean apparatus of the lion (F. leo) and related species of Felidæ|journal=Annals and Magazine of Natural History|volume=18|issue=104|pages=222–229|year=1916|last1=Pocock|first1=R.I.|url=https://zenodo.org/record/2453999}}</ref> based on whether the [[hyoid bone]] of the [[larynx]] is incompletely ("roarers") or completely ("purrers") [[ossified]]. However, Weissengruber et al. argued that the ability of a cat species to purr is not affected by the anatomy of its hyoid.<ref>{{cite journal|doi=10.1046/j.1469-7580.2002.00088.x|pmid=12363272|pmc=1570911|title=Hyoid apparatus and pharynx in the lion (Panthera leo), jaguar (Panthera onca), tiger (Panthera tigris), cheetah (Acinonyx jubatus) and domestic cat (Felis silvestris f. catus)|journal=Journal of Anatomy|volume=201|issue=3|pages=195–209|year=2002|last1=Weissengruber|first1=G. E.|last2=Forstenpointner|first2=G.|last3=Peters|first3=G.|last4=Kubber-Heiss|first4=A.|last5=Fitch|first5=W. T.}}</ref>

The "roaring cats" (lion, ''Panthera leo''; tiger, ''P. tigris''; jaguar, ''P. onca''; leopard, ''P. pardus'') have an incompletely ossified hyoid, which, according to this hypothesis, enables them to roar but not to purr. However, the [[snow leopard]] (''Uncia uncia'', or ''P. uncia''), as the fifth felid species with an incompletely ossified hyoid, purrs.<ref>{{cite journal|doi=10.2307/3503882|jstor=3503882|title=Uncia uncia|journal=Mammalian Species|issue=20|pages=1–5|year=1972|last1=Hemmer|first1=Helmut|doi-access=free}}</ref>

All remaining species of the family Felidae ("purring cats") have a completely ossified hyoid, which enables them to purr but not to roar. Based on a technical acoustic definition of roaring, the presence of this vocalization type depends on specific characteristics of the vocal folds and an elongated vocal tract, which  is rendered possible by an incompletely ossified hyoid.