In fact, James M. Bower and others have argued, partly on the basis of these structures and partly on the basis of cerebellar studies, that the cerebellum itself is fundamentally a sensory structure, and that it contributes to motor control by moving the body in a way that controls the resulting sensory signals. Despite Bower's viewpoint, there is also strong evidence that the cerebellum directly influences motor output in mammals. Even the earliest anatomists were able to recognize the cerebellum by its distinctive appearance. Aristotle and Herophilus (quoted in Galen) called it the παρεγκεφαλίς ("parenkephalis"), as opposed to the ἐγκέφαλος ("enkephalos") or brain proper. Galen's extensive description is the earliest that survives. He speculated that the cerebellum was the source of motor nerves. Further significant developments did not come until the Renaissance. Vesalius discussed the cerebellum briefly, and the anatomy was described more thoroughly by Thomas Willis in 1664. More anatomical work was done during the 18th century, but it was not until early in the 19th century that the first insights into the function of the cerebellum were obtained. Luigi Rolando in 1809 established the key finding that damage to the cerebellum results in motor disturbances. Jean Pierre Flourens in the first half of the 19th century carried out detailed experimental work, which revealed that animals with cerebellar damage can still move, but with a loss of coordination (strange movements, awkward gait, and muscular weakness), and that recovery after the lesion can be nearly complete unless the lesion is very extensive. By the beginning of the 20th century, it was widely accepted that the primary function of the cerebellum relates to motor control; the first half of the 20th century produced several detailed descriptions of the clinical symptoms associated with cerebellar disease in humans. The name "cerebellum" is a diminutive of "cerebrum" (brain); it can be translated literally as "little brain". The Latin name is a direct translation of the Ancient Greek παρεγκεφαλίς ("parenkephalis"), which was used in the works of Aristotle, the first known writer to describe the structure. No other name is used in the English-language literature, but historically a variety of Greek or Latin-derived names have been used, including "cerebrum parvum", "encephalion", "encranion", "cerebrum posterius", and "parencephalis".