The pains of hypochondriasis, when they assume any more definite form than that of mere dyspeptic uneasiness, present many analogies with neuralgia. They are not, usually, periodic in any regular manner, but they have the same tendency to complete intermission, and they frequently haunt some one or more definite nerves for a considerable period of time. Of all nerves that are liable to this kind of affections the vagus is undoubtedly the most susceptible; hypochondriac patients very frequently complain of pseudo-anginoid and pseudo-gastralgic pains; next in frequency are nervous pain in the region of the liver, or in the rectum or bladder. The main distinctions by which they are separable from true neuralgia are two: in the first place, the character of the pain nearly always is more of the boring or burning kind than of the acutely darting sort which is most usual in true neuralgia; and, secondly, the influence of mental attention in aggravating the pain is far more pronounced than in the latter malady; indeed, it is often possible, by merely engaging the patient in conversation on other topics, to cause the pain to disappear altogether for the time. But in hypochondriasis it is not often that we are left, for any long time, to these means of diagnosis only; the special character of the disease is that the morbid sensations shift from one place to another, in a manner that is quite unlike that of the true neuralgias. The patient who to-day complains of the most severe gastralgia, or liver-pain, will to-morrow place all his sufferings in the cardiac region, or in the rectum, or will complain of a deep fixed pain within his head; and these changes are often most rapid and frequent. Frequently there are also peculiar skin sensations, which usually approach formication in type, and these, like the pains, are apt to shift with rapidity from one part of the body to another. Later on in the disease, especially in those worst cases which approach most closely to the type of true insanity, there are often hallucinations of a peculiar and characteristic nature, such as the conviction of the patient that he has some animal inside him gnawing his vitals, that he is made of glass and in constant danger of being broken, and a variety of similar absurdities. In short, it is not the fully-developed cases of hypochondriasis that need puzzle us, these are usually distinct enough; but the earlier and less characteristic stages in which pain may be nearly the only symptom that is particularly prominent. In hypochondriasis, as in hysteria, there is often great sensitiveness of the surface; and, as in hysteria, this sensitiveness is found to be very superficial, so that a light touch often hurts more than firm, deep pressure. As in hysteria, too, the tenderness is a phenomenon so greatly affected by the mind, that, if we can divert the patient's attention for a moment, he will let us touch him anywhere, without noticing it at all.