Very rare offprint from the first series (in quarto) of the Biologische Untersuchungen. The present paper on the anatomy and comparative anatomy of the labyrinth of the ear is from a scientific point of view Retzius’ most important work. It appeared at the same time as he published his great Das Gehörorgan der Wirbelthiere, the most magnificent work ever published on the comparative anatomy of the ear. The two figures of the human ear labyrinth on the double-page plate, drawn by Retzius himself, is said to be unsurpassed in scientific exactness and mark the highest level in Retzius’ entire scientific production (numbering over 350 papers). “Retzius described the ‘Retzius bodies’ in the labyrinth” (Garrison-Morton 1566). “The number and scope of Retzius’ scientific publications were unique in his time. He presented the results of his research in more than 300 papers devoted to descriptive macroscopic and microscopic anatomy, comparative anatomy, embryology, anthropology, zoology, botany, and pathological anatomy. Retzius was very concerned with the presentation of his illustrations . . . Most of his papers were in the New Series of Biologische Untersuchungen . . . Within its field this publication was unique . . . (Dict. Scient. Biography). Collation: Pp 32. Two lithographed plates (one double-page) and wood-engraved images in the text. Binding: Uncut in the original printed wrappers as issued. References: Garrison-Morton 1566.