Hypochondriasis is not insanity, if by insanity we mean intellectual perversion dependent mainly or entirely on the state of the higher nervous centres. But it is closely allied to insanity in its phenomena, only that these are, as it were, manifested in a scattered form, unequally distributed over the whole central nervous system, and especially affecting the spinal sensory centres. And its radical relationship to true insanity is strongly indicated by the fact that the sufferers from hypochondriasis are nearly, if not quite, always members of families in which distinct insanity has shown itself; indeed, more often than not, of families which have been strongly tainted in this way. In the majority of instances there are psychical peculiarities of a marked kind which accompany or precede the development of the abnormal sensations which form the especial torment of hypochondriacs. Without apparent cause, they begin to evince a heightened self-feeling and an anxious concentration of their thoughts upon the state of one or more of their bodily organs. Or it may be that, before any such definite bias is given to their thoughts, they simply become less sociable and more self-centred, and are subject to fits of indefinite and inexplicable depression, or at least to great variability of spirits. But before long they begin to experience definite morbid sensations, most commonly connected with the digestive organs, and very often accompanied by positive derangement of digestion of an objective character; such as flatulence, sour eructation, spasmodic stomach-pain, etc. Along with these phenomena, or soon afterward (and not unfrequently before the patient has acquired that intensity of morbid conviction of his having some special disease which is afterward so marked a peculiarity of his mental state), he very often becomes the subject of the kind of pains which it is the special purpose of this chapter to describe.