A series of cases exhibiting lesions in different parts of the brain were studied for any changes caused in consciousness and emotion or what seemed to be the physiological counterparts of these faculties.In no lesion of the right hemisphere (in hight-handed persons) was any consistent disturbance in these two faculties observed. Not one of 33 cases of left hemiplegia exhibited confusion and only three an equivocal emotional instability.Lesions of the frontal, parietal, occipital and temporal lobes on the left similarly caused no definite disorder of consciousness and emotion.In an extensive vascular lesion of Head's speech zone, despite jargon asphasia and apraxia, the patient remained generally wellbalanced, alert to happenings about him, and capable of appreciating their general import. Hence the conclusion that emotion and consciousness (in the sense of awareness alone) were not affected and therefore do not reside in this part of the cortex.It was eminently in the right hemiplegias, which generally arise from left capsular injuries, that definite and permanent confusion of consciousness was found (27 out of 55 cases of old hemiplegia). It seems, therefore, that an area somewhere in the left base is concerned with the maintenance of awareness.In these same right hemiplegias and in other lesions that certainly or inferentially affect basal structures directly or indirectly were found restlessness, irritability, delirium and other forms of instability, thus indicating that emotion is localized in the base and possibly is confined to the left side.All the conclusions are regarded as tentative and subject to revision in the light of further evidence. The method of following psychological faculties through a series of brain injuries is believed to be a useful one and worthy of wider employment.