Eustachius is credited with several anatomical discoveries, among them the tensor tympani muscle and the Eustachian tube, published in his chapter entitled De auditus organis. In the last respect, however, he was anticipated by Alcmaeon, about 500 BCE. Eustachius was the first to describe the chorda tympani as a nerve. Plate VIII illustrates the “Eustachian valve”, the valvula venae cavae in the right auricle. Eustachius recognized the thoracic duct in the horse and even detected some of its valves. His work on this structure was forgotten until Aselli’s description of the lacteals. This work includes first description of the adrenals. Several of the plates deal with the structure of the kidney.
Basing his work on the dissection of fetuses and newborn children, Eustachi was the first to study the teeth in any considerable detail. In his Libellus de dentibus attached to this work he provided an important description of the first and second dentitions and described the hard outer tissue and soft inner structure of the teeth. He also attempted an explanation of the problem of the sensitivity of the tooth’s hard structure. The Libellus has a separate title page dated 1563. It was reprinted with German translation, Wien, Urban & Schwarzenberg, 1951. It was translated into English by Joan H. Thomas and edited and introduced by David A. Chernin and Gerald Shlklar as as A little treatise on the teeth. The first authoritative book on dentistry (1563) (Canton, MA, 1999). Eustachi’s illustrations of the teeth were first published in his Tabulae anatomicae, edited by Giovanni Maria Lancisi (No. 391). For further information, including a discussion of the states of the Opuscula, see the entry at HistoryofInformation.com at this link.
Digital facsimile of the 1563 edition from the Internet Archive at this link.