practise does not suffice to learn what a normal person gets with one or two repetitions. Memory seems essentially unaffected in dementia præcox and in the manic-depressive psychoses, though it may be masked by confusion, apathy or stupor. These factors are mainly responsible for the poorer performance in memory tests that most other pathological cases show.
Various attempts have been made to experiment with the suggestibility of mental life, as by measuring the extent to which judgments could be influenced by suggestion. Scott's ingenious experiments showed that this could be different in different functions, so that we might not speak of general suggestibility any more than we should speak of general sensory acuity. But as an acute sense of sight would be much more important for our behavior than an acute sense of smell, a relatively great importance doubtless attaches to suggestibility in the higher levels of conduct, though the level of human activity where suggestibility really counts be not represented in experiments on the simpler sensory and motor processes. In a sense, the distractible manic case might be called over-suggestible because he catches up the examiner's interjected phrases and weaves them into his talk, or is easily diverted from one thing to another. But it is in the hysterical and in some dementia præcox mechanisms that suggestibility is increased to the point of giving real control over conduct. The Lata of the East Indies, and the Jumpers of the lumber camps are the most conspicuous examples of the former. Here we see an automatic, positive response to the idea suggested. In dementia præcox this occurs, but is not so very common. The striking feature of heightened suggestibility in dementia præcox is that it is negative to the suggestion. Not only may the individual be "blocked," as we say, making no response whatever, but so far as possible the opposite response may be made. It represents the extreme of the "contrariness" that is met with in normal life. It even may become possible to direct the individual's actions through asking the opposite of what one wishes; but the negativism is strictly to the idea conveyed. These cases know what they are about, and when it is clear that the thing wished is the opposite of the thing suggested, it is no longer obtained in this way. Bleuler has given a unified formulation of how this symptom is related to the underlying psychosis to which latter I shall subsequently allude.
Individual differences occur in a number of mental processes more involved than the above, which are but slightly subject to experiment. There is no reason to suppose any specific alteration of sense imagery as a result of mental disease. But those hyperfunctionings of it that we call hallucinations are quite different in various mental disorders. There is a delirious type of hallucination produced by poisons, like alcohol, morphine and cocaine, generally visual, and not especially sys-
