<P> His colleague, Jean - Baptiste Lamarck, named a number of vestigial structures in his 1809 book Philosophie Zoologique . Lamarck noted "Olivier's Spalax, which lives underground like the mole, and is apparently exposed to daylight even less than the mole, has altogether lost the use of sight: so that it shows nothing more than vestiges of this organ ." </P> <P> Charles Darwin was familiar with the concept of vestigial structures, though the term for them did not yet exist . He listed a number of them in The Descent of Man, including the muscles of the ear, wisdom teeth, the appendix, the tail bone, body hair, and the semilunar fold in the corner of the eye . Darwin also noted, in On the Origin of Species, that a vestigial structure could be useless for its primary function, but still retain secondary anatomical roles: "An organ serving for two purposes, may become rudimentary or utterly aborted for one, even the more important purpose, and remain perfectly efficient for the other...(A) n organ may become rudimentary for its proper purpose, and be used for a distinct object ." </P> <P> In the first edition of On the Origin of Species, Darwin briefly mentioned inheritance of acquired characters under the heading "Effects of Use and Disuse", expressing little doubt that use "strengthens and enlarges certain parts, and disuse diminishes them; and that such modifications are inherited". In later editions he expanded his thoughts on this, and in the final chapter of the 6th edition concluded that species have been modified "chiefly through the natural selection of numerous successive, slight, favourable variations; aided in an important manner by the inherited effects of the use and disuse of parts". </P> <P> In 1893, Robert Wiedersheim published The Structure of Man, a book on human anatomy and its relevance to man's evolutionary history . The Structure of Man contained a list of 86 human organs that Wiedersheim described as, "Organs having become wholly or in part functionless, some appearing in the Embryo alone, others present during Life constantly or inconstantly . For the greater part Organs which may be rightly termed Vestigial ." Since his time, the function of some of these structures has been discovered, while other anatomical vestiges have been unearthed, making the list primarily of interest as a record of the knowledge of human anatomy at the time . Later versions of Wiedersheim's list were expanded to as many as 180 human "vestigial organs". This is why the zoologist Horatio Newman said in a written statement read into evidence in the Scopes Trial that "There are, according to Wiedersheim, no less than 180 vestigial structures in the human body, sufficient to make of a man a veritable walking museum of antiquities ." </P>

What happens to muscles that remain unused for a period of time