After 1861, physiology took the lead, and kept it. But, through all the work, science and practice have been held together; the facts of experimental physiology have been and are tested, every inch of the way, by the facts of medicine, surgery, and pathology. The infinite minuteness and complexity of the investigation, and its innumerable side-issues, are past all telling. They who are doing the work, in science and in practice, have always had in their thoughts the fear of fallacies in the interpretation of these highest forms of life. Sir William Gowers, fourteen years ago, wrote as follows of the earlier workers:-- "Doubt was formerly entertained as to the existence of differentiation of function in different parts of the cortex, but recent researches have established the existence of a differentiation which has almost revolutionised cerebral physiology, and has vastly extended the range of cerebral diagnosis. The first step of the new discovery was constituted by the clinical and pathological observations of Hughlings Jackson, which suggested the existence, on each side of the fissure of Rolando, of special centres for the movements of the leg, arm, and face. These observations led to the experiments of Ferner, which resulted in the demonstration of the existence in the cortex of the lower animals of well-defined regions, stimulation of which caused separate movements, or evidence of special sense excitation, while the destruction of the same parts caused indications of a loss of the corresponding function. Hence he came to the conclusion that these regions constitute actual motor and sensory centres. Ferrier had, however, been anticipated in many of these results by two German experimenters, Fritsch and Hitzig, whose results, differing a little in detail, correspond closely in their general significance. Many other investigations of the same character have since been made, of which those of Munk are especially important. The original observations of Hughlings Jackson left little doubt that the general facts, learned from experiments on animals, are true of man; and this conclusion has been to a large extent confirmed by pathological and clinical observations directed to the verification on man of the pathological results. To this verification the labours of Charcot and his coadjutors have largely contributed. But the verification has already made it probable that some differences exist between the brain of man and that of higher animals (even of monkeys), and that the conclusions from the latter cannot be simply transferred to the former."