Free public domain audiobooks: LibriVox
https://librivox.org/ The world of free audio-books opens up in this site, starting with children's literature. There are collections of various subjects, biographies and more. For the medical domain, click Browse by Genre, scroll down till you reach "Non fiction>Medical". Click this link and you find Grays Anatomy, works by Sir William Osler, Edward Jenner, Florence Nightingale's Notes on Nursing and more treasures!