The spinal cord is the center of reflex acts; that is, if the leg of a brainless frog is touched with acid, he will take the other leg to wipe it off with. There are, as we have seen, substations in the skin, hence the acid causes the sensation of a foreign body, word is telegraphed the spinal cord, where there is a large central station; from here word is sent out by another set of nerves, to move the leg away from the acid, but this being insufficient, word is telegraphed to the other leg to wipe off the offending substance. Did the same thing happen in the body, at the same time that the cord telegraphed word to the affected member to withdraw it, it would telegraph the brain, and the sensation of pain would be felt. A message travels along a nerve at the rate of about thirty-six yards a second, or a mile a minute. This is about the time made by a lightning express train. The distance in the body being so short, the time taken is imperceptible, and we say that movement is instantaneous. The paths traveled by nerve impulses are made passable by use; the oftener an impulse traverses a given route, the more adapted such a route becomes for future traffic. But all of this has to do with the nerves which are under the control of the will. There is another set of telegraph wires in the body, called the sympathetic or vegetative system, so-called because it presides over the processes of nutrition and is beyond the control of the will. =The Hygiene of Work.=—Since the motor centers are located in the brain, it is natural to expect that all definitely directed movements will directly affect the brain and the mental development, and so it is. Du Bois Réymond says that it is easy to demonstrate that such bodily exercises as gymnastics, fencing, swimming, riding, dancing, and skating are much more exercises of the central nervous system, of the brain, and spinal cord than of the muscles. It is further urged that healthful energy of will is impossible without strong muscles, which are its organs, and that endurance, self-control, and great achievement all depend on muscle habits. The philosophy of work consists in its necessity. The brain-cell in health cannot cease to be active, except to a partial extent during sleep. There must be some output of mind from the mind cell and of motor stimulus from the motor cell. The proper selection of work for that particular brain to do, and the physiologic regulations of the work done, is the basis of the hygiene of work. For health, for happiness, and for efficiency, right work rightly done is the most important matter in any man’s or any woman’s life.