The question of the site of origin of the clonic and the tonic elements of convulsive seizures has been much debated. Much experimental and clinical evidence has been adduced to support the contention that the cortex is the source of the clonic and that subcortical mechanisms are responsible for the tonic parts of the motor disturbances, but it has been demonstrated experimentally by a number of investigators, including ourselves,1 that clonic convulsions can be produced in animals after the total excision of the cortical motor areas of both sides of the brain.
In this paper we shall limit ourselves to a consideration of some features of this problem and shall attempt to give a solution that is based on a large series of experiments on animals, which have led us to apply to the question the ideas of Hughlings Jackson2 on the change in the quantity of nervous