When one of these patients is encouraged to talk he often tells how he had felt himself overpowered by the horrors of his surroundings and forced to make increased efforts to keep going and avoid showing his condition to his fellows--in other words, to repress his emotions. The strain continuing, the shell-burst proved the last straw, and his repressed feelings broke into consciousness and took possession of it; this is what the man called being 'unconscious', but the condition is really an abrupt dissociation. In course of time--hours, days, or even weeks--he comes to himself again, and once more his feelings are buried; but now he is a hysteric, and his buried feelings--his dissociated stream--produce and maintain his symptoms. In whatever way the hysteria arises the developed symptoms are the result of a mental activity which is powerful enough to overcome for a long time the desire for recovery. There are two streams of thought--the one desirous of cure and the other engaged in keeping up the symptoms--and we recognise an extreme example of continuous dissociation, in which the main stream is not only unaware of the existence of the other and unable to control it, but in which the results produced by the dissociated stream are antagonistic to the desires of the main personality. This conception accords fairly well with Janet's definition as given above, but though it gives us a description of the disease and indicates its relation to other phenomena we have yet to understand why the dissociation occurs. This is a difficult problem, and one to which several answers can be given. I have suggested one above, and Freud supplies another, which he applies not only to hysteria but to allied nervous conditions. What follows is not an exposition of his ideas, but rather my interpretation of such as are acceptable and useful to me. A complex, which according to Freud usually centres around an infantile sexual desire, is repugnant to the consciousness and becomes repressed as a result of conflict in just the same way as a memory is repressed. The complex is kept thrust down in the unconscious, but always tends to produce effects; it may do so in dreams or may obtain symbolic representation in the form of a neurosis, especially in times of stress. Besides the primary aim of expressing repression by a symbolic representation, Freud admits a 'secondary function' of the neurosis by which the patient may derive some advantage from the disease.