THE AUDITORY TUBE was described in some detail by Eustachius in 1563. The structure was mentioned again by Valsalva in 1717. In 1818 Carus published his observations on amphibian embryos. He found structures suggestive of the gill structures in fish and concluded that the development of the eustachian tube was related to the respiratory tract. In 1825 Rathke published similar conclusions from his work with pig embryos. By the end of the 19th century the theory that the middle ear complex developed from the pharynx was universally accepted. The exact mechanism of development, however, is contested to this day.
Hammar1 of Upsala, using wax reconstruction, studied fetuses from three weeks to birth. He described three stages of development: (1) the anlage period; (2) the demarcation period; and (3) the transformation period.
In the first period (three to seven weeks) a slit-like pouch develops from the first visceral groove of
Proctor B. Embryology and Anatomy of the Eustachian Tube. Arch Otolaryngol. 1967;86(5):503–514. doi:10.1001/archotol.1967.00760050505008
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