=Diagnosis.=—First, the common age of onset during puberty and adolescence, fourteen to twenty-four in the vast majority of cases, this being the only common mental disease occurring during this age period. Second, the progressive character terminating in mental enfeeblement or deterioration, that is “dementia” proper. Third, the evidence of defect or deficiency symptoms indicating that the patient’s mind has altered in the sense of deterioration from its former normal condition, whereas, in imbeciles or idiots the mind has failed to develop in the first place. Fourth, in the earlier stages particularly the marked dissociation of the brain powers, some being well maintained as memory and orientation (that is knowledge of time and space), others being weakened, such as judgment, power of attention and the like. Fifth, the early appearance of the emotional defect, a remarkable indifference and apathy of the patient to people and surroundings, the patient being unsocial and taking no interest in anything. Sixth, all the peculiar motor reactions, which are mentioned above under the catatonic head, and which very rarely occur in any other mental disorder. Seventh, the delusional content nearly always refers to the patient’s exterior, forces outside of him, people or things which are exerting an unfavorable influence upon him, delusions of persecution and reference. The patient practically never accuses himself, as is the rule in cases of true melancholia, never blames himself, but always the other party or the other force outside of him. Eighth, the delusions of grandeur are usually indicative of a stage of deterioration. =Prognosis.=—Some authorities are inclined to doubt if any case ever completely recovers, claiming that in apparent recovery it may have been a question of mistaken diagnosis, or that the recovery is more apparent than real, that the patient is not truly well, or will have a relapse, so that a permanent cure will be impossible. Other authorities admit the possibility of recovery though in a very small minority of cases. The statistics of the Still-Hildreth Sanatorium, covering more than two-hundred fifty cases show total recoveries of at least one-third. This includes all types and all stages of progress, many being advanced on entrance. Of the less advanced cases and those of not more than two or three years’ standing there have been some fifty per cent recovery. Many cases make improvement or become stationary in greatly improved condition, but are not included in the thirty per cent. Of the three types, the catatonic offers the best prognosis, the hebeprhenic the poorest, while the paranoiac occupies an intermediate position.