3. The fit may remain localized to the region first affected, or, as is more commonly the case, may spread to other regions. In the latter case the various motor areas are affected in a certain definite order, according to their cortical arrangement. Thus, a fit arising from irritation of the right cortical face-area leads first to twitchings, then to convulsions, and perhaps finally to paralysis on the contralateral face-muscles, the movements then spreading from the face to the upper extremity, and from the arm through the trunk to the lower extremity. When the fits become generalized, spreading to the opposite side of the brain, the cortical areas are affected in the reverse order. 4. The patient should retain consciousness throughout the attack. 5. The fits should not be succeeded by any paresis or paralysis. Later on, when the fits become more frequent and severe, they lose their typical Jacksonian characters, the various regions being affected so rapidly one after the other that all focal symptoms tend to be obscured. The fits are then often associated with definite loss of consciousness, and succeeded by paresis or paralysis of the parts primarily affected. The patient also usually complains of lassitude or headache, this lasting some hours after the termination of the fit. Traumatic epilepsy does not always partake of the typical Jacksonian type. Sometimes the fits are so sudden in onset and violent in character that, from the first, the more typical features are absent. Again, fits of the focal or Jacksonian type do not necessarily imply that some pathological causative agent will be found on exploration. Ordinary epilepsy sometimes partakes of the focal type. I have myself operated on three cases of focal epilepsy, deceived by their Jacksonian characteristics, and found nothing abnormal. On the other hand, in all these cases definite and permanent improvement was observed subsequent to the surgical procedures. It might also be added that encouraging reports are to hand, not only in cases of idiopathic epilepsy with focal symptoms, but also in cases without focal symptoms. A decompression operation is carried out on the basis of Kocher’s statement to the effect that the fit is immediately preceded by a rise of intracranial pressure, for which a safety-valve must be supplied--such as is afforded by an intermusculo-temporal operation of decompression. Whether Kocher’s statement is correct or not, the fact remains that some cases of idiopathic epilepsy, without focal symptoms, benefit considerably from operation.