I say to a subject: "Of course you remember that we went to Potsdam yesterday, and took a' drive on the Havel ? " The suggestion takes effect, and he at once begins to relate all that he believes we did in Potsdam. This is a retroactive positive hallucination, because the hypnotic believes that he has experienced something that never really occurred. The following would be a retroactive negative hallucination, as the hypnotic forgets something which did happen. I say to him: "You have not had any dinner; you have not had any breakfast." Upon which he immediately feels hungry, as he thinks he has had nothing to eat since he got up.

Many motor disturbances of which I have before spoken may be reckoned as related to amnesia, or loss of memory. For example, when I tell somebody that he cannot lift his arm, or that he cannot speak, I am sometimes dealing with loss of memory, because a movement is made impossible if the memory of it cannot first be called up. This is the case in those paralyses which some French authors (Binet, Fere) call paralysies systematiques - a paralysis for a special act. Such a paralysis is not followed by total functional incapacity of a whole group of muscles; the function is rather interfered with for one particular use only. The incapacity to say a, or to sew, for example, would be a paralysis for a special act; if the person could not speak or move his arm at all, this would be a complete paralysis. It is possible in this way to deprive the subject of all memory of the letter a for a considerable time, so that he can neither speak nor write it. It is possible to produce almost all kinds of aphasia experimentally, as Kussmaul, Arndt, and others have demonstrated.

We can cause any one to forget a language he has learned - French, for example (Forel, Frank); we can make writing impossible (agraphia). By a suitable suggestion a hypnotic can be deprived of the power of making himself understood by facial expression (amimia). Drawing, sewing, every form of activity, in fact, can be prevented by suggestion.

There is a particular group of disturbances of speech in which the power of speaking is more or less lost, though the perception of words remains intact (motor aphasia). It is easily induced by suggestion. But we can go farther, and not only deprive a subject of the power of speaking but also of the perception of speech, or even of any particular word or letter. It is possible to deprive him of the very idea which he attaches to a letter - a, for example. This difference will become clear if we observe the behaviour of a person under the different circumstances. If he retains the idea of the letter he is conscious of his inability to utter it; he is aware that he is speaking or writing nonsense, because he has no letter a, and even tries to avoid words in which that letter appears (Max Dessoir). But if he is deprived of the conception or idea of a letter, he is no longer surprised that he cannot write or speak it. This becomes still more interesting in posthypnotic suggestion. It is possible to cause a post-hypnotic loss of memory, and to make the subject at the same time replace one letter by another. I told a hypnotic that after he was awakened he would always say e instead of a. I woke him, and asked, "Are you awake?" "Je" (Ja), he replied.

When asked what he had been doing, he replied: "Ich neb' geschlefen "(Ich habe geschlafen). The subject laughed, but was at the same time slightly annoyed because he could not utter the letter a, and was perfectly aware that he was talking nonsense. But if the idea a were also missing, or had been replaced by the idea e, the subject would say e instead of a without observing it.

I have shown above that subjects may be made to forget certain of their experiences (negative retroactive hallucinations). In the same way, whole periods can be made to vanish from a subject's consciousness. Mr. X., who is forty-three years old, was told, "You no longer remember anything that has happened to you since you were thirty." This sufficed to cause a blank in X.'s consciousness. He was unable to answer any questions about this period; he did not know how he made my acquaintance, nor how he got into my room; when such questions were put to him he invariably shrugged his shoulders and answered, "I don't know."

It is possible to carry this still farther, and transport the subject back to an earlier period of life. In this case the subject finds no gaps in his memory; he believes that he is living in this earlier time, and brings his present surroundings into relation with it.

Here is the case of a man who fought at St. Privat in the French War. I suggested to him that he was younger, and in the battle. He stood up at once, gave military orders, and commanded the artillery to open fire. When I asked him if he knew Dr. Moll, he said, "My doctor's name is R------. I do not know Dr. Moll." He knew nothing that had happened since the day of the battle; he was totally unaware of the rheumatism for which I was treating him; he said he was quite well. When I asked him who I was, he replied he did not know. It was interesting that he could not be induced to retreat; I tried to make him take a few steps backward, but he replied, "I will not retreat one step without orders." I suggested that the enemy was approaching, but nothing would induce him to retreat. When I drew his attention more and more upon myself, and told him that he must know who I was, the situation suddenly altered. He recognized me, and knew his real age, but had no notion of what had just passed.

A lady, aged thirty-four, whom I caused to believe that she was eight years old again, asked for her doll, spoke in a childish voice, cried when she thought I was about to take her doll away, and called for her mamma.

Finally, it is possible to make a person believe that he has never been born. Even this suggestion will be accepted, and the consciousness will be an absolute blank.