Artificial organ almost always preceded by extensive experiments with animals. Initial testing in humans is frequently limited to those either already facing death or who have exhausted every other treatment possibility. Artificial arms and legs, or prosthetics, are intended to restore a degree of normal function to amputees. Mechanical devices that allow amputees to walk again or continue to use two hands have probably been in use since ancient times, the most notable one being the simple peg leg. Since then, the development of artificial limbs has progressed rapidly. New plastics and other materials, such as carbon fiber have allowed artificial limbs
Artificial gills (human) Artificial gills (human) Artificial gills are unproven conceptualised devices to allow a human to be able to take in oxygen from surrounding water. This is speculative technology that has not been demonstrated in a documented fashion. Natural gills work because nearly all animals with gills are thermoconformers ("cold-blooded"), so they need much less oxygen than a thermoregulator ("warm-blood") of the same size. As a practical matter, therefore, it is unclear that a usable artificial gill could be created because of the large amount of oxygen a human would need extracted from the water. Several potential methods exist for the development