As we have seen in the preceding lessons, an emotion is the more complex phase of feeling. As a rule an emotion arises from a number of feelings. Moreover, it is of a higher order of mental activity. As we have seen, a feeling may arise either from a physical sensation or from an idea. Emotion, however, as a rule, is dependent upon _an idea_ for its expression, and always upon an idea for its direction and its continuance. Feeling, of course, is the elemental spirit of all emotional states, and, as an authority has said, is the thread upon which the emotional states are strung. Halleck says: "When representative ideas appear, the feeling in combination with them produces emotion. After the waters of the Missouri combine with another stream, they receive a different name, although they flow toward the gulf in as great volume as before. Suppose we liken the feeling due to sensation to the Missouri River; the train of representative ideas to the Mississippi before its junction with the Missouri. Emotion may then be likened to the Mississippi _after_ its junction--after feeling has combined with representative ideas. The emotional stream will not be broader and deeper than before. This analogy is employed only to make the distinction clearer. The student must remember that mental powers are never actually as distinct as two rivers before their union. * * * The student must beware of thinking that we have done with feeling when we consider emotion. Just as the waters of the Missouri flow on until they reach the gulf, so does feeling run through every emotional state." In the above analogy the term "representative ideas," of course, means the ideas of memory and imagination as explained in previous chapters. There is a close relation between emotion and the physical expression thereof--a peculiar mutual action and reaction between the mental state and the physical action accompanying it. Psychologists are divided regarding this relation. One school holds that the physical expression follows and results from the mental state. For instance, we hear or see something, and thereupon experience the feeling or emotion of anger. This emotional feeling reacts upon the body and causes an increased heart beat, a tight closing of the lips, a frown and lowered eyebrows, and clinched fists. Or we may perceive something which causes the feeling or emotion of fear, which reacts upon the body and produces pallor, raising of the hair, dropping of the jaw, opening of the eyelids, trembling of the legs, etc. According to this school, and the popular idea, the mental state precedes and causes the physical expression.