The Croonian Lectures On Cerebral Localisation

ulation of the different regions included within this area. How these movements are to be interpreted is a subject on which there are great differences of opinion. The definite purposive character of the movements, however, their correspondence with the ordinary volitional activities of the animals, and, above all their uniformity and predictability, harmonise best, in my opinion, with the hypothesis that they are indications of the functional excitation of centres directly concerned in effecting volitional movements, and anatomically a part of the motor apparatus. It has been established by experiments on monkeys?and now so generally admitted that it is almost unnecessary to enter into detailed proof?that destruction of the centres, excitation of which produces definite movements causes paralysis (qua volition) of the same movements on the opposite side of the body, varying in degree, completeness, and duration with the extent i f the destruction of the respective centres. When the destruction is complete the paralysis is permanent, and is followed in due course by descending degeneration of the pyramidal tracts of the spinal cord, and secondary contracture in the paralysed limbs. As an illustration I quote the fallowing experiment on a monkey which was exhibited at the International Medical Congress in London, 1881, eight months after the operation. The cortex was destroyed as shown in the figure (Fig. 33), in the left hemisphere over an area embracing the as...