Rare first edition of one of the great books in dentistry, the first important specialized monograph on the anatomy of the teeth and one that remained an authoritative source for hundreds of years. The Libellus de dentibus was issued, with separate title-leaf dated 1563, as the second part of Eustachii Opuscula anatomica (1564), but may also have been published separately. Eustachius was born at San Severino, near Ancona. He was physician to the Duke of Urbino, and then to the duke’s brother, Cardinal Guilio della Rovero, whom Eustachius followed to Rome in 1549. There he was invited to join the medical faculty of the Sapienza as the equivalent of professor of anatomy, and was permitted to obtain cadavers for dissection from the hospitals of Santo Spirito and Consolozione. With advancing years Eustachius was so severely afflicted by gout that he was compelled to resign his chair. His fame as an anatomist rests principally on a series of copper engravings of the skeleton and muscles, which were sadly not published until 140 years after his death. In this respect he resembled Leonardo da Vinci in that his anatomical achievement was very much greater than the influence which he exerted, and this for a similar reason. The text is lost and the copperplates for his anatomical atlas remained unprinted and forgotten in the Vatican library until discovered in the early 18th century. They were then presented to Pope Clement XI who gave them to his physician Lancisi, who published them with his own notes in 1714 as Tabulae Anatomicae, which also contains illustrations of Eustachius’ detailed study of the teeth and jaws. It is said that if this work had appeared in 1552 Eustachius would have ranked with Vesalius as one of the founders of modern anatomy. Eustachius ”discovered the Eustachian tube, the thoracic duct, the adrenals and the abducens nerve, and gave the first accurate description of the uterus. He also described the cochlea, the muscles of the throat and the origin of the optic nerves ” (Garrison-Morton). In his Libellus de dentibus, the first book ever published devoted entirely to the dental field, Eustachius gives us a complete anatomical description of the teeth and their development in every age of growth from early uterine life until the eruption of the third molar. A small volume of only 95 pages, it covered accurately the anatomy, embryology, and physiology of the teeth, including the blood and nerve supply. Collation: Pp (8), 95, (1). Title page and last page with printer’s woodcut device. First and last leaves mounted on old paper. The last nine leaves reinforced in outer margin with loss of letters at the end of the lines and the two final leaves with loss of whole words. The missing text is replaced by hand-writing in ink. Binding: Early uncoloured paper boards. Provenance: Engraved bookplate: John Wessler (1864–1927), dentist, inventor of a famous tooth-brush bearing his name. He wrote on dental history and was a keen collector. In 1923 he donated his great Apollonia collection to Tandläkarinstitutet. References: Garrison-Morton 3668; Guerini, pp 178-88; Crowley 1465; Durling 1408 (Opuscula), Heirs of Hippocrates 322 (1564 edition); Grolier 21 (Opuscula); Weinberger, History of Dentistry, pp 279-82; Norman 739 (Opuscula anatomica); DSB, vol. IV, pp 486-88; Wellcome I, 2091 (Opuscula). Waller 10615.