Middle ear to sounds of higher frequency, because these are better taken up by the inner ear (which also responds to higher frequencies than those of non-mammals). The malleus, or "hammer", evolved from the articular bone of the lower jaw, and the incus, or "anvil", from the quadrate. In other vertebrates, these bones form the primary jaw joint, but the expansion of the dentary bone in mammals led to the evolution of an entirely new jaw joint, freeing up the old joint to become part of the ear. For a period of time, both jaw joints existed together, one medially and one
Multi-anvil press first compression stage by introducing the removable hatbox design, allowing ordinary machine presses to be converted into multi-anvil systems. A variety of assembly designs have been introduced and standardized including the Walker castable, and the COMPRES assemblies. Recent advances have focused on in-situ measurements(link to next section), and standardizing materials and calibrations. A typical Kawai cell 8-6 multi-anvil apparatus uses air pumps to pressurize oil, which drives a vertical hydraulic ram to compress a cylindrical cavity known as a hatbox. This cavity is filled with six steel anvils, three facing and three facing down, that converge on a set of