Treat headache as a danger signal, by rest and the removal of its cause, and it will prevent at least ten times as much suffering and disability as it causes. CHAPTER XVIII NERVES AND NERVOUSNESS Nerves are real things. In spite of their connection with imaginary diseases and mental disturbances, there is nothing imaginary or unsubstantial about them. There is no more genuine and obstinate malady on earth than a nervous disease. Because nerves lie in that twilight borderland between mind and matter, body and soul, the real and the ideal, the impression has got abroad that they are little better than figures of speech. Though their disturbances give rise to visions of all sorts there is nothing visionary about them; they are just as genuine and substantial a part of our bodily structure as our bones, muscles, and blood-vessels. In fact, it was this very substantiality that at the beginning prevented their proper recognition, and handicapped them with their present absurd and inappropriate name. "Nerve" is from the Greek _neuron_, meaning tendon, or sinew, and was originally applied indiscriminately to all the different shining cords which run down the limbs and among the muscles. In fact the first recognition of nerves was an utter failure to recognize. The tendon cords, which are the ropes with which the muscles work the joint pulleys, were actually included under one head with the less numerous but almost equally large and tough cords of grayer color, flatter outline, and less glistening hue, which were afterwards found to be nerve-trunks. Cutting either paralyzed the limb below the cut,--and what more proof could you ask of their having the same function? Such is the persistence of ancient memories, that any physician could tell you of scores of cases in which he has heard the naive remark, in reference most frequently to a deep gash across the wrist, that the "nerves" were cut, and the hand was paralyzed, when what had happened was simply that the tendons had been cut across. When, after centuries of blundering in every possible direction until the right one was finally stumbled upon (which is the mechanism of progress), it was realized that some of these "nerves," the grayer and flatter ones, carried messages instead of pulling ropes, they were still far from being properly understood. It is an amusing illustration of the blissful ignorance and charming naivete which marked their study and discussion at this time, that nerves were for centuries regarded as hollow tubes, carrying a supply of "animal spirits" from the central reservoir of the brain to the different limbs. So seriously was this believed, that, in amputations, the cut nerve-trunks were carefully sought out and tied, for fear the vital spirits would leak out and the patient thus literally bleed to death. One can imagine how this must have added to the comfort of the luckless patient.