There are three bones located in the inner ear: the incus, the malleus and the stapes. Collectively, all three comprise the ossicles. Sound vibrates these bones, after it has traveled from the external ear, through the ear canal and beyond the tympanic membrane. The sound waves then vibrate the ossicles, and those vibrations travel into the cochlea, where sound is translated to nervous system signal to the brain. The incus lays at the center of the ossicles, connecting the malleus to the stapes. It is shaped like an anvil, which is why "the anvil" is a widely used alternative name for the bone. The bone has a few basic regions. The surface for the malleus articulates with malleus ossicle. The bone has two extensions known as the long and short crus. At the end of the long crus, the lenticular process curves into a hooked shape. The center of the incus is also known as the body. The incus has been a well known part of the ear for centuries. Alessandro Achillini first wrote of it in the 1500s.