Lever Lever A lever ( or ) is a simple machine consisting of a beam or rigid rod pivoted at a fixed hinge, or fulcrum. A lever is a rigid body capable of rotating on a point on itself. On the basis of the location of fulcrum, load and effort, the lever is divided into three types. It is one of the six simple machines identified by Renaissance scientists. A lever amplifies an input force to provide a greater output force, which is said to provide leverage. The ratio of the output force to the input force is the mechanical advantage
Jan Lever evolutie" (1956; English translation 1958 under the title "Creation and Evolution"). In 1970, Lever was elected member of the Royal Netherlands Academy of Arts and Sciences. In the early 1950s, Lever started research on the neuroendocrine system of the basommatophoran snail, "Lymnaea stagnalis". Lever himself found a particular kind of neurons in the ancylid snail "Ferrissia", and his student Joos Joosse demonstrated those neurons in other snail species. "Lymnaea" became the animal of choice for physiological research at the VU Amsterdam laboratory for decades. At the beginning of his career, Lever’s ideas about evolution and the species concept were inspired