While attention might be called to other more or less common inciters of nervousness, what we wish to emphasize here are those cases which are not due to causes commonly understood. For instance, we meet with patients who are apparently in good physical health, who are intelligent, who live in optimistic surroundings, who have, apparently, every reason to be happy. Many have faced death many times without flinching. Yet they are the preys of fears which, by others than physicians, would be called foolish. Thus, to illustrate by a simple example, a man who is to all appearances a tower of physical strength and will power comes to the physician complaining of indigestion, insomnia, backache, or what not. These complaints the physician finds are but reflections of some mental problem, or worry. And the thing which is really at the bottom of the patient's ills is found to be concerned with street cars. Street cars, the patient says embarrassedly, make him feel nervous, afraid; he is anxious, doubtful, disturbed whenever he sees or hears one, thinks of one, or is on a street where there are car tracks. He is troubled even by trains; should he ride in a train he is uneasy until the journey is over. He does not know why he should cringe before so illogical a fear, yet he feels powerless in preventing it. He admits the folly of it, but his own reasoning and that of others does not mend matters. Generally, he says, he suffers from his phobia but slightly; when business, domestic, or other problems are trying it seems to come to new life and vigour, and to remain with him for months after his other problems have been removed. It is evident that he is unhappy, and mentally tortured. These cases are the most difficult of solution. It does no good to reason with the patient, advise him not to worry; and there is no pill which will dissolve his mental thorn. Years of experience among just such patients have shown psychologists, however, that in many instances of unreasonable fears, obsessions, impulses, etc., the underlying cause is some past painful experience which has been forgotten. In the example given above, it is found that many years ago the patient was in a street car accident in which several people were killed. He was very much frightened at the time, and the incident remained in his memory for quite a while. But because he did not like to think of it, since it disturbed his mental peace, he repressed the memory every time it tried to come to consciousness, and gradually the memory faded from consciousness, and from recollection; he forgot it, in other words. Though forgotten, it still lived, buried among other past experiences, where it became a disturber of the mental harmony.

Doubtless it will be difficult for many readers to understand how unpleasant experiences of the past, which are not within voluntary recall, can cause strange worries of one sort or another. Each of us has had many painful experiences but we do not seem to be much the worse for them. However, if asked for an explanation, we might say that the persons most likely to suffer because of these experiences are the so-called sensitive or impressionable; their mental peace is easily disturbed. Again, many of the experiences are received in childhood when the mind is very open to suggestion, and when the reasoning powers are immature. Often, too, the experiences are repressed, kept out of consciousness. If the individual were not inclined to take things too much to heart, so to speak, if he reasoned that the experience in question was powerless to harm him further, if he did not strive to keep it from consciousness, he would not be likely to suffer. Since the opposite conditions obtain in many persons, painful experiences often become firmly impressed upon the mind; they are card-catalogued as harmful with a capital H. Then it happens that the individual meets with something which has a resemblance to the painful incidents of the past, which stirs up the unconscious mind, where the memories repose. The latter prompts consciousness to be on guard, that there is some danger in the things met with. What danger there could be in them is unknown; the memories have been forgotten, and thus the motive of the unconscious mind is hidden.

However we choose to regard what has been said, clinical testimony gives ample evidence of the continuity of painful experiences in certain persons. It also demonstrates how quickly a cure is effected once the painful memory is exposed. This is natural, because we lose fear and are willing to fight valiantly once we know the nature of our antagonist; if we do not know what, of countless dangers, we are to face we tend to be timorous, afraid of almost everything.

Thanks to the patient researches of medical psychologists, many useful methods have been devised whereby the mind may be explored and its thorns plucked out. Unlike the body, the mind cannot be X-rayed, ausculated, subject to various chemical tests. Again, few object to physical examinations, but countless are averse to revealing their thoughts. And the patient is not of very great help; unlike the man who has heart disease he does not complain about his heart and direct our attention to this organ; the nervous person complains of a variety of troubles that might be due to any number of causes. Thus, the task of the medical psychologist is quite great.

At one time hypnotism was much used for mental exploration, and it was found to be valuable in some instances. However, it is being employed less and less. Many persons cannot be hypnotized, many object to it, many are unsuitable for it, and there exists a common prejudice against it.

Another method is the so-called hypnoidization method of Sidis. In this the patient remains as quiet as possible, keeping his attention fixed for a time on some stimulus, as the monotonous beats of a metronome. When this is over the patient is asked to concentrate on the symptoms relating to his malady, and tell freely the thoughts that come to him. By this method it is often found that many unpleasant, forgotten incidents of the past can be resurrected.