Cochlea a protein motor called prestin on their outer membranes; it generates additional movement that couples back to the fluid–membrane wave. This "active amplifier" is essential in the ear's ability to amplify weak sounds. The active amplifier also leads to the phenomenon of soundwave vibrations being emitted from the cochlea back into the ear canal through the middle ear (otoacoustic emissions). Otoacoustic emissions are due to a wave exiting the cochlea via the oval window, and propagating back through the middle ear to the eardrum, and out the ear canal, where it can be picked up by a microphone. Otoacoustic emissions
Traditional Chinese medicines derived from the human body centuries after Li Shizhen considered the bioethical and biomedical dilemmas of using human drugs, 20th-century technological and medical advances have raised new related questions of organ transplants, transplantation medicine, organ trade, tissue banks, human cloning, and the commodification of human body parts (Awaya 1999, Nie 2002, Scheper-Hughes and Wacquant 2002). Traditional Chinese medicines derived from the human body Li Shizhen's (1597) "Bencao gangmu", the classic materia medica of traditional Chinese medicine (TCM), included 35 human drugs, including organs, bodily fluids, and excreta. Crude drugs derived from the human body were commonplace in the early history of medicine. Some of these