Karl Gerster, a physician intimately acquainted with homoeopathy, gave a scientific demonstration in a discussion he had with the homoeopaths that homoeopathy requires revision from the standpoint of suggestion.

Hypnotism has also enriched our knowledge by enabling us to understand the pathogenesis of certain diseases. I refer here to the importance of auto-suggestion as a factor in the genesis of disease. Charcot already had admitted that paralyses of traumatic origin often depend on the patient's autosuggestion that some limb could not be moved. In recent years there has been considerable discussion as to the extent to which auto-suggestion may be responsible for other nervous phenomena of traumatic origin. It was recognized that when the victim of an accident is convinced that his injuries are bound to bring on an illness, some symptom or other of disease will appear. Krafft-Ebing and Wichmann are among those who take this view, and even if others - Meynert, for instance - have contested the importance of auto-suggestion, the number of investigators who ascribe essential importance to this psychological factor in the production of the neuroses which follow accidents is permanently on the increase. Hypnotism has also contributed indirectly to our knowledge of the pathogenesis of traumatic neuroses by placing the general importance of mental influence in a right light.

Thus, it has been pointed out that the quarrels and litigation nowadays forced on a person who has been hurt in an accident often prove more injurious than the accident itself. Finally, many people are unable to fight against possible pathological sequela^ because they hope to derive a permanent income from the accident. That these psychological moments play a chief part in the causation of traumatic neuroses had long been recognized by Striimpell, especially as regards the wish to acquire'an annuity; later on, Jolly, F. C Muller, Lauenstein, O. Binswanger, F. Schultze, Mittelhauser, and others expressed the same view. It is particularly in Germany that this question plays so great a part, on account of the Law of Compulsory Insurance against Accident. The cruel fact of being driven to work often enough restores a man to health when he has been injured in an accident, but the possibility of obtaining an annuity without working for it diminishes the desire for work and the capability of carrying it out.

But hypnotism has thrown more light on hysteria than it has on neuroses of traumatic origin, I have already mentioned (p. 303) that Mobius considers all those bodily pathological changes hysterical that are caused by ideas. In recent times other authors also have attempted more and more to put hysteria on a psychological basis. When one reads the works of authors like Mobius, Charcot, Hellpach, Eulenburg, Crocq, and others, it is not difficult to understand how the investigation of hysteria has been influenced by hypnotism. Many of the authors who have recently studied this branch of the subject have put forward suggestibility as a common characteristic of hysteria and hypnosis, which is generally taken to mean that hysteria is characterized by auto-suggestibility, and hypnosis by external suggestibility. Of course it must not be assumed that the exclusively psychological view of hysteria is the only correct one; that is a point which cannot as yet be decided. But there is one point on which we may rest assured, and that is, that psychological factors play a great part in these diseases, and that their recognition will be essentially advanced by the study of hypnotism.

Of course, this question possesses only a theoretical significance. When a trouble that is considered to be hysterical or neurasthenical is caused by some malignant psychic influence, we know how to combat it prophylactically and therapeutically. Daily experience teaches us that an uncongenial environment will cause or aggravate a disease. There are few people who are not affected by being constantly told on all sides that they look ill, and I believe that just as much injury is done by an accumulative mental process of this kind as by chemical poisons. Suggestion produces suffering, just in the same way that it cures it. Doctors who are incapable of understanding mental influence aright may easily cause unpleasant results by making thoughtless remarks. Forel mentions a case in which a patient suffered from headache for years, because it was, as he believed, said of him when suffering from inflammation of the lungs accompanied by headache that this would never pass away. Whether or not the patient misunderstood the doctor is immaterial - the working of suggestion appears here. Forel succeeded by hypnosis and counter-suggestion in rapidly removing the headache.

Lcewenfeld mentions similar cases; for example, one in which a patient believed he was suffering from a severe heart trouble, because of a thoughtless remark made by his doctor. Brugelmann shows that many attacks of asthma are caused by the patient's belief that he cannot breathe; the patient awaits with anxiety the moment for the attack to appear, and this anxiety brings on the attack. A powerful diversion of the attention may sometimes suffice to diminish the intensity of the attack.

There are many cases in which it is uncertain whether the action of a remedy is suggestive or somatic, and it is the same with the pathogenesis of certain diseases. Some doctors favour a suggestive origin, others a somatic. For some years past attention has been drawn to the connection between affections of the nose and certain phenomena presented by the womb. Some say that nasal treatment influences menstruation by suggestion, and others oppose this view. Even if we assume that the action here takes place by the way of natural reflex paths, and that the process should be. distinguished from suggestion, the possibility still remains that suggestion has a great influence.

Hypnotism has also thrown light on the nature of many idiosyncrasies, for such at times arise from auto-suggestion. There are people whom coffee does not constipate but purges, and patients on whom drugs and other remedies have the contrary effect to that expected. A lady who was given bromide as a sedative, remarked: "Strange, I've had that before and it only excited me." Morphia only increased pain in her case. Many of these cases are the result of autosuggestion, and hypnotism in giving us the key to a large number of idiosyncrasies has at the same time taught us many an important lesson. But we must, of course, refrain from ascribing every idiosyncrasy to auto-suggestion, because idiosyncrasies may depend on purely somatic conditions. Many people suffer from urticaria after eating crab; but they also have urticaria when they do not know that they have had any crab. Naturally, we cannot, even in the present day, invariably decide whether the idiosyncrasy is of mental or physical origin.