In this historical review we summarize the work of the Dutch physician, chemist, and anatomist Gerard Blaes (Blasius). A detailed account of his life and work is presented with emphasis on his contribution to anatomy. In particular, special reference is made to his innovative description of the spinal cord and spinal nerves. Blasius's contributions to neuroanatomy are remarkable when taking into account the limited technology of his era. As a true man of his era, he made significant contributions in research and teaching of anatomy, botany, and chemistry. He published a detailed description of the spinal cord with its gray and white matter and the spinal nerve roots, which significantly increased the knowledge of neuroanatomy in his era. He also is considered one of the founders of comparative anatomy through his work in both humans and animals.