Supernumerary body part considered to have lost much or all of their original function through evolution. These body parts can be classed as additional to the required functioning of the body. In human anatomy the vermiform appendix is sometimes classed as a vestigial remnant. Prosthesis is an artificial extension that replaces a body part, and cybernetics is the study of computer technology in relation to organisms which can include replacement or additional body parts. Body integrity identity disorder (BIID) is a psychiatric disorder in which a person thinks that they have one or more additional limbs than they should, despite having two arms
Environmental medicine studies viruses, bacteria and fungi are not within the scope of environmental medicine, if the spread of infection is directly from human to human. However, infections that are water-borne (e.g. cholera and gastroenteritis caused by norovirus or campylobacteria), or food-borne, are typical concerns of environmental medicine. Its role is preventive as far as possible. Much of epidemiology, which studies patterns of disease and injury, is not within the scope of environmental medicine, but e.g. air pollution epidemiology is a highly active branch of environmental health and environmental medicine. In addition, any disease with a large genetic component usually falls outside