This brings me to the fourth phenomenon, - suggestibility. By a "suggestion" is meant any impression or idea which tends to produce in the subject some change other than itself, more especially to produce an act of some kind. "Suggestibility" is a state in which such tendencies are strengthened, in many cases so much so that they are practically sure of realization. Suggestions are usually given in the form of commands, but anything which expresses the wishes of the hypnotizer, and sometimes impressions not connected with the hypnotizer, will produce an effect. For instance, the "wax like catalepsy" so often observed is merely the realization of a suggestion which the hypnotizer conveys by placing the subject's limbs in a given position, - the subject takes the hint and keeps them there. Anything which the hypnotizer says to another person in the subject's hearing, or even a hint conveyed by a tone of voice, will often serve as effectually as the most positive command. Suggestibility is a chief factor in the production of controversies among observers of the phenomena, for, unless one is on his guard, he is apt to find in his subject just what he expects to find and no more.

Suggestibility varies much in degree and is often subject to curious and apparently arbitrary limitations. I have usually found the muscles suggestible in proportion to the degree of paralysis. In one of my subjects, for example, the eyelids, lips, tongue and fingers were paralyzed and they obeyed my every command. But the arm was only weakened, not helpless, and when I told the subject he could not lift that arm he disobeyed me and did it, - with difficulty it is true, but still he did it. In another the left hand was totally paralyzed, the right but slightly. I ordered the forefinger of the right hand to wag, - ■ there was no apparent result. Two or three minutes afterwards I saw that forefinger wagging violently and had much difficulty in stopping it. Here the suggestibility existed, but it was imperfect and I was never able to improve it. The right hand, however, I could never affect at all.

To the subject this suggestibility presents itself under various forms. Sometimes the muscles seem to obey the commands of themselves, the subject looking on, so to speak, but having no part in producing the result. In other cases the suggestion seems to be realized only through the subject's own will; he must consent before it can be carried out. He then sometimes feels that he must obey, whether he will or no; at others he feels as though he could refuse but "didn't care to make the effort/' or thought he "might as well oblige" the hypnotizer. How far these feelings of the subject's are illusory is an open question, but I think there are always limits to the hypnotizer's power of imposing upon the subject suggestions which he finds repugnant, and a more careful study of these limitations is one of the things most needed in hypnotism.

The fifth phenomenon to which I shall call attention is the post-hypnotic state together with the notion of sub-consciousness which is often irresistibly suggested by it. Occasionally a suggestion given during the hypnotic state spontaneously outlasts the state itself. Thus, I once told the subject of whom I have above spoken, - the one whose finger responded so slowly to the suggestion to wag, - that his left hand was stiff. No apparent effect. A little later I woke him and found that his hand was as rigid as a bar of iron; neither he nor I could do anything with it at all and I had to hypnotize him again to undo the locked muscles. Here the suggestion refused to include itself in the general command "wake up," and persisted into the waking state. An analogous phenomenon, - and this is what is commonly known as the "posthypnotic suggestion" - can be produced in nearly all cases by telling the subject to do so and so when a specified signal is given, - the signal being given only after he awakes.

The study of the relation which such post-hypnotic suggestions bear to the normal consciousness into which they are intruded is the most interesting and has proved one of the most valuable fields, of study offered by hypnotism, for it has thrown a flood of light upon some of the most perplexing phenomena of hysteria, - in particular upon the "sub-conscious fixed idea" and "double personality." Sometimes the subject has not the least idea that the act in question has been imposed upon him by another; he fancies that he does it of his own motion and will allege the most plausible reasons for wholly purposeless acts. For example, a subject who had been told to open and then close the door upon a given signal, when asked why he did it said, "I thought I heard a dog in the hall." Very often the subject, while performing the post-hypnotic suggestion, relapses temporarily into an hypnotic state.

Sometimes there is reason to believe that states of consciousness which appear in the hypnotic state, persist after the subject has awakened in a sort of subterranean or, more exactly, sub-conscious form, quite unknown to his waking consciousness. Suppose the subject be told that after he awakes he is to do so and so as soon as the hypnotizer has used the word "and" ten times. Punctually upon the utterance of the tenth "and" the suggestion will be executed. Clearly the "ands" were being counted. Yet if the subject be questioned about it before the tenth "and" has been reached, he will not have the least idea how many "ands" have been used, and will stoutly protest that he never dreamed of counting them. What, then, did the counting? If you hypnotize him he will tell you immediately how many "ands" have been used, and will say that he was counting them all the time. This is the very simplest form of the class of phenomena to which "double personality" belongs, - a class of phenomena the importance of which to psychological theory cannot be-overestimated.

The sixth and last phenomenon to which I shall" call attention is that of rapport. In most hypnotic states only the hypnotizer has access to the hypnotized mind. To his every word the patient is keenly alive, but he is dead to all else. The spontaneity of this phenomenon has been contested of late and it has been ascribed to suggestion. My own experience leads me to believe that it is the normal result of the manipulations which produce the hypnotic state, being due to the fact that the hypnotizer never allows his subject to lose consciousness of him though consciousness of all else falls away.