The following observations are founded upon the records of 301 autopsies performed by myself at Rainhill Asylum. They are concerned principally with certain abnormal and morbid manifestations which occur within the crania of the insane. Of these the chief are, on the one hand, indications of subevolution, as shown by macroscopic structural defects of the cerebral hemispheres, such as deficiency of weight or of convolutional complexity, and on the other, evidence of dissolution as exhibited by wasting of the cerebral hemispheres. The relationship existing between these abnormal and morbid manifestations and certain other intracranial appearances is also discussed. No attempt, however, has been made—for reasons which will afterwards be given—at any close correlation between these abnormal and morbid manifestations and the mental states recorded during life. The observations, therefore, are of a pathological rather than a clinical nature.