The process begins, then, with something which is to the psychical organism no more than a boil or a corn is to the physical. In consequence of some suggestion from without, or of some inherited tendency, a small group of psychical units set up a process of exaggerated growth which shuts them off from free and healthy interchange with the rest of the personality. The first symptom of disaggregation is thus the _idée fixe_, that is to say, the persistence of an uncontrolled and unmodifiable group of thoughts or emotions, which from their brooding isolation,--from the very fact of deficient interchange with the general current of thought,--become alien and intrusive, so that some special idea or image presses into consciousness with undue and painful frequency. The fixed idea, thus originating, may develop in different ways. It may become a centre of explosion, or a nucleus of separation, or a beginning of death. It may induce an access of hysterical convulsions, thus acting like a material foreign body which presses on a sensitive part of the organism. Or it may draw to its new parasitic centre so many psychical elements that it forms a kind of secondary personality, co-existing secretly with the primary one, or even able at times (as in some well-known cases) to carry the whole organism by a _coup-de-main_. (Such changes, it may be noted in passing, are not always for the _worse_.) Or, again, the new quasi-independent centres may be merely _anarchical_; the revolt may spread to every cell; and the forces of the environment, ever making war upon the organism, may thus effect its total decay.