Bartolomeo Eustachi (1500 or 1514 – 27 August 1574), also known by his Latin name of Eustachius, was one of the founders of the science of human anatomy.
He came from San Severino, near Macerata, Italy, and was a contemporary of Vesalius, with whom he shares the reputation of having created the science of human anatomy.
He is known as a supporter of Galen and extended the knowledge of the internal ear by rediscovering and describing correctly the tube that bears his name. He is the first who described the internal and anterior muscles of the malleus and the stapedius, and the complicated figure of the cochlea. He is the first who studied accurately the anatomy of the teeth, and the phenomena of the first and second dentition. Eustachius also discovered the adrenal glands (reported in 1563). His greatest work, which he was unable to publish, is his "Tabulae Anatomicae" Anatomical Engravings. Completed in 1552, nine years after Vesalius was published, the author feared ex-communication by the Catholic Church.
The fact that his book became a bestseller more than a century after his death shows the extent of the religious restrictions on anatomists all through the Renaissance.
Eustachius did not confine his researches to the study of relative anatomy. He investigated the intimate structure of organs with assiduity and success. What was too minute for unassisted vision he inspected by means of glasses (early microscopes). Structure that could not be understood in the recent state he unfolded by maceration in different fluids, or rendered more distinct by injection and exsiccation. The facts illustrated by these figures are so important that it has been said that, if the author had been fortunate enough to publish them, anatomy would have attained the perfection of the 18th century at least two centuries earlier.