The organs for muscle-and-joint sense consist of tiny spindles distributed around the joints and embedded within the mass of the muscles. They are arranged so as to be affected by every motion of a joint or every contraction of a muscle. They register not only the fact of motion but also the extent. There is a disease, commonly known as locomotor ataxia, in which the muscle-and-joint sense is impaired or lost, particularly in the legs. The result is that walking becomes difficult and unsteady, and usually impossible when the eyes are shut or the room is dark. This is because the victim learns to make his sight serve instead of his muscle-and-joint sense for guiding his muscular movements, and when this also is withdrawn all knowledge of where his legs are or what they are doing fails, and the only course is to fall down or lie down as quickly as possible. We have some additional bodily sensations, such as nausea, repletion, fatigue, ill feeling or _malaise_, which guide our conduct more or less, and are not very different in consciousness from hunger or thirst. So far as is known there are no sense organs by which these sensations are aroused. They are not strictly senses, therefore. We do not know enough about how they originate to say anything more about them. The _contact senses_ are touch, warmth, cold, and taste. Pain that comes as the result of bodily injury might also be classified as a contact sense, since its cause is something that comes in direct contact with the body from outside, but it differs from internal pain only in its source and not at all in the sensations it arouses, so there is no need of describing it over again. The sense of touch is the fundamental sense; the very lowest animals, even those that have no specially developed sense organs, and few organs of any kind, react to the contact of objects with their bodies just as the highest animals react to the sense of touch. When no other information is available, that of simple contact guides the animal in its securing of food and its avoidance of harm. In accordance with this primitive character of the touch sense, the psychologists tell us that we interpret the information from our more highly developed sense organs, sight particularly, in terms of the feel of objects. When we look at anything our judgment of it actually consists in an idea of how it would feel if we were to take hold of it. Our touch organs consist of tiny spots scattered all over the surface of the body. They are much closer together on some parts than on others. The total number is estimated at a half million or more. A good way to test their sensitiveness is by pressing down on different parts of the skin with fine hairs. When this is done it is found that the most sensitive regions--the tip of the tongue, for instance--are fifty or sixty times as sensitive as the dullest regions, like the small of the back. To obtain sensations of touch it is necessary that there be