Animal magnetism, also known as mesmerism, was a protoscientific theory developed by German doctor Franz Mesmer in the 18th century in relation to what he claimed to be an invisible natural force (Lebensmagnetismus) possessed by all living things, including humans, animals, and vegetables. He claimed that the force could have physical effects, including healing. He tried persistently, without success, to achieve a wider scientific recognition of his ideas. The vitalist theory attracted numerous followers in Europe and the United States and was popular into the 19th century. Practitioners were often known as magnetizers rather than mesmerists. It had an important influence in medicine for about 75 years from its beginnings in 1779, and continued to have some influence for another 50 years. Hundreds of books were written on the subject between 1766 and 1925, but it is no longer practiced today except as a form of alternative medicine in some places. Etymology and definitions "Magnetizer" The terms "magnetizer" and "mesmerizer" have been applied to people who study and practice animal magnetism. These terms have been distinguished from "mesmerist" and "magnetist", which are regarded as denoting those who study animal magnetism without being practitioners; and from "hypnotist", someone who practises hypnosis. The etymology of the word magnetizer comes from the French "magnétiseur" ("practicing the methods of mesmerism"), which in turn is derived from the French verb magnétiser. The term refers to an individual who has the power to manipulate the "magnetic fluid" with effects upon other people present that were regarded as analogous to magnetic effects. This sense of the term is found, for example, in the expression of Antoine Joseph Gorsas: "The magnetizer is the imam of vital energy". "Mesmerism" A tendency emerged amongst British magnetizers to call their clinical techniques "mesmerism"; they wanted to distance themselves from the theoretical orientation of animal magnetism that was based on the concept of "magnetic fluid". At the time, some magnetizers attempted to channel what they thought was a magnetic "fluid", and sometimes they attempted this with a "laying on of hands". Reported effects included various feelings: intense heat, trembling, trances, and seizures. Many practitioners took a scientific approach, such as Joseph Philippe François Deleuze (1753–1835), a French physician, anatomist, gynecologist, and physicist. One of his pupils was Théodore Léger (1799–1853), who wrote that the label "mesmerism" was "most improper". Noting that, by 1846, the term "galvanism" had been replaced by "electricity", Léger