The question how far disease of the surface of the brain may reveal itself by symptoms which point to the exact position of the morbid process, is one of considerable interest, not only in a physiological point of view, in relation to the functions of the convolutions, or from a diagnostic standpoint, as indicating the seat of the diseased action, but also in a therapeutic aspect, in showing where local treatment may probably be most beneficially carried out. In order, however, to be able to decide whether certain symptoms indicate disease in an organ, it is clearly of great consequence that we should know what are the functions of that organ in health. Regarded in this light recent experimental researches into the nature of the cerebral functions, and especially those located in the hemispherical ganglia, are of no small value to the physician. True, very many of the results obtained by such observers as Hitzig and Ferrier, are still problematical; but though this be granted in reference to their more detailed observations, there are certain of their broad general conclusions—those, particularly, that have been corroborated by pathology—which may now be considered as well nigh established on a firm basis of fact; and I make this remark, notwithstanding the vigorous and hostile criticism of Dr. Brown-Séquard. Amongst these conclusions the one with which we are here most concerned, is, that the convolutions bounding the fissure of Rolando are charged with motor function, especially in the upper and lower extremities.