The Eustachian tube is a passageway that lies between the middle ear and the pharynx, the upper part of the mouth located just below the top of the nose. One of the primary functions of the tube is to equalize ear pressure between the middle ear and the atmosphere; most of the time the tube is closed, but it can open to let in a small amount of air to prevent damage to the ear. Early mentions of the tube dates back to Alcmaeon of Sparta around 500B.C., who constructed a basis for understanding medicine via dissection, and thought the tube enabled goats to breathe through their ears as well as noses. Other Greek philosophers, including Aristotle and Celsus, also vaguely referred to the tube’s existence, but did not elaborate on its function or purpose.
The surge of Italian anatomists during the Renaissance period and their emphasis on dissection brought forth new understandings of the body and its parts. Andreas Vesalius (1514-1564), Professor of Anatomy of Padua, provided detailed descriptions of two of the tiny bones in the middle ear (the malleus and incus), but although he was aware of the existence of the Eustachian tube, he does not comment on its role in hearing. His contemporary, Bartholomeus Eustachius (1510-1574) who held the Chair of Anatomy at Rome, published the first detailed anatomical description of the tube in his 1562 Epistola de auditus organis (Examination of the Organ of Hearing), possibly the first treatise on the ear:
It originates at the anterior course of the base of the skull, and takes an anterior course toward the pterygoid process of the sphenoid bone. It consists of two parts: the first solidly connected with the temporal bone, close to the tympanic cavity; the second soft, partly ligamentous, partly cartilaginous, directed towards the nasopharyx. Cross sections of the tube are not perfectly round and the inner part is twice as wide as the outer.
Comparing the tube to a quill pen, Eustachius provided precise descriptions of its structure and position in the face, but he made no mention of its function:
Nor did he publish an engraving of the tube as part of the external auditory system in his 1651 Tabuli Anatomiceu, which also contained detailed figures of the ear ossicles and the tympanum membrane in man and dog. It is likely that Eustachius held the long-standing belief that the Eustachian tube functioned as (another) avenue for breathing, since he postulated that other parts of the ear, especially the ossicles and tympanum, were involved in the mechanism of sound transduction. Not until 1683, with the work of French anatomist Guichard Joseph DuVerney (1648-1730) was this belief corrected. In Traité de l’organe de l’ouie, DuVerney described the Eustachian tube as a means for renewing air within the tympanum and for equalizing air pressure, believing that the tube was always open and it was the eardrum that maintained the flow of air.
Descriptions of the Eustachian tube contained more than just anatomy: they highlighted the physiological and therapeutic importance of diagnosing and treating ear diseases confined to the Eustachian tube or tympanum. Antoine Maria Valsalva (1666-1732) is historically credited for giving the tube its eponymous name in honor of Eustachius, whose work set the foundation for understanding the anatomy and physiology of the ear. Valsalva, a pupil of the famed physician Marcello Malpighi (1628-1694), was appointed Professor of Anatomy at the University of Bologna in 1705, where his main interests were on anatomy and the function of the middle and internal ear.
In 1705, Valsalva published De aure humana tractatus, which followed years of intense observations, animal experiments, and numerous dissections; the treatise included enhanced descriptions of the physiology and pathology of the ear, even demonstrating communication between the mastoid cells and the tympanic cavity. Valsalva also outlined the function of the Eustachian tube and its diagnostic use; the tube, he claimed, worked alongside the pharyngeal muscles of the ear. Believing that Eustachian tube blockages were among the main causes of deafness, in De aure, Valsalva also outlined his “Valsalvian maneuver,” a method consisting of the forced expiration of air through the Eustachian tube with the mouth and nostrils closed, thus resulting in increased pressure to the tympanic membrane. The procedure dates back to Arab physicians in the 11th century and was used as a remedy for cleansing the middle ear from pus, and hence, unblocking the ear and restoring hearing.
 Charles D. Bluestone, Eustachian Tube: Structure, Function, and Role in Otitis Media, Vol.2 (PMPH-USA, 2005), 4.
 Translated & quoted in Bluestone, Eustachian Tube, 5.
 Most of Eustachius’ works were not published during his lifetime or simply lost. His copper plates of anatomical engravings were discovered early in the eighteenth century and presented by Pope Clement XI to his physician Lanncisi (1655-1720), who then published the plates in 1712. Unlike Vesalius, Eustachius’ plates represented dead, not living anatomy.
 Steven H. Yale, “Antonio Maria Valsalva (1666-1723), Clinical Medical & Research 3: 35-38. The Valsalva maneuver remains a staple in modern medicine, having been adapted as a diagnostic procedure in modern cardiology for assessing heart murmurs and heart failure.