The first device for [[stereotactic]] surgery was described in detail in [[1908]] by British neuroscientist and surgeon Sir [[Victor Horsley]] and British physiologist [[Robert Henry Clarke]]. This device, named the [[Horsley-Clarke apparatus]], facilitated the study of the [[cerebellum]] in [[animal]]s by enabling accurate electrolytic lesioning to be made in the brain. To ensure that a lesion would be introduced in the correct site, Horsley and Clarke created [[atlas]]es containing pictures of the brains of the animals on which they experimented. Shortly thereafter, in [[1918]], the first stereotaxic apparatus for humans was designed by Canadian neurologist Aubrey Mussen. However, the first attempts at stereotaxic surgery in human subjects were not made until the 1940s; these attempts were pioneered by American neurologists [[Ernest A. Spiegel]] and [[Henry T. Wycis]]. Since then, a number of modifications and refinements have been made to stereotaxic devices, procedures, and atlases, and these advances have significantly improved the utility of [[stereotaxy]].