The first thing that a medical student has to learn is that appearances are _not_ deceptive--except to fools. Every line of the human figure, every proportion of a limb, every detail of size, shape, or relation in an organ, _means_ something. Not a line upon any bone in the skeleton which was not made by the hand-grip or thumbprint of some muscle, tendon, or ligament; no bump or knuckle which is not a lever or hand-hold for the grip of some muscle; not a line or a curve or an opening in that Chinese puzzle, the skull, which was not made to protect the brain, to accommodate an eye, to transmit a blood-vessel, or to allow the escape of a nerve. Every minutest detail of structure means something to the man who will take the pains to puzzle it out. And if this is true of the foundation structure of the body, is it to be expected that the law ceases to run upon the surface? Not a line, not a tint, not a hollow of that living picture, the face, but means something, if we will take the time and labor to interpret it. Even coming events cast their shadows before upon that most exquisitely responsive surface--half mirror, half sensitive plate--the human countenance. The place where the moving finger of disease writes its clearest and most unmistakable message is the one to which we must naturally turn, the face; not merely for the infantile tenth part of a reason which we often hear alleged, that it is the only part of the body, except the hand, which is habitually exposed, and hence open to observation, but because here are grouped the indicators and registers of almost every important organ and system in the body. What, of course, originally made the face the face, and, for the matter of that, the head the head, was the intake opening of the food-canal, the mouth. Around this necessarily grouped themselves the outlook departments, the special senses, the nose, the eyes, and ears; while later, by an exceedingly clumsy device of nature, part of the mouth was split off for the intake of a new ventilating system. So that when we glance at the face we are looking first at the automatically controlled intake openings of the two most important systems in the body, the alimentary and the respiratory, whose muscles contract and relax, ripple in comfort or knot in agony, in response to every important change that takes place throughout the entire extent of both.