In 1954 a taming point in medical history, resulting from applied bionics, was the first' open heart' surgery done in Minneapolis, Minnesota, by Dr. W. Lillehei's techniques for the first time allowed the patient to be operated on while blood was supplied to the patient from a donor. Today 'open heart' surgery , using more complicated methods and bionic devices, is common in the United States. Important technological advances such as those already mentioned have encouraged scientists to develop the artificial heart. Early in 1983, in its first use by a human patient, a medical team at the University of Utah Medical Center replaced the diseased heart by a Jarvik-7. The world watched amazed as television pictures of Dr. Clark showed him as he improved steadily after the surgery. His continued life demonstrated that a bionic device could imitate the action and function of a healthy heart. Dr. Clark lived for 112 days. Life-like or bionic machines have existed for several centuries. The development of tools by man's ancestors is a good example of the application of bionics to extend human capabilities. Modern bionic research is especially involved in prosthetics devices that substitute for, or replace lost or diseased body parts such as arms, legs, and eyes. Recent advances in electronics have enabled scientists to make better use of electrical impulses in the control of prosthetic devices. One interesting research project is the development of an artificial eye in which video signals are transformed into light patterns that are sent into nerve receptors in the patient. The future for applied bionics seems to be promising. Existing bionic devices will become smaller, faster, and more effective. The artificial heart used for Dr. Clark is only one of experimental replacement devices. It is likely to be joined in the future by replacements for other internal systems or organs. Bionic livers, stomachs, and lungs are not impossibillties ! Which of the following does this passage mainly discuss?