As fear supplies the energy for running, so anger fits us for fight,--and for nothing but fight. The mechanism is almost identical with that of fear. Brain and liver, adrenals and thyroid are the means, but the emotion presses the button and releases the energy, stopping all digestion and energizing all combat-muscles. The blood is flooded with fuel and with substances which, if not used, are harmful to the body. We were never meant to be angry without fighting. The habit of self-control has its distinct advantages, but it is hard on the body, which was patterned before self-control came into fashion. The wise man, once he is aroused, lets off steam at the woodpile or on a long, vigorous walk. He probably does not say to himself that he is a motor animal integrated for fight and that he must get rid of glycogen and adrenalin and thyroid secretion. He only knows that he feels better "on the move." The wiser man does not let himself get angry in the first place unless the situation calls for fight. However, the fight need not be a hand-to-hand combat with one's fellow man. William James has pointed out that there is a "moral equivalent for war," and that the energy of this instinct may be used to reinforce other impulses and help overcome obstacles of all sorts. A good deal of the business man's zest, the engineer's determination, and the reformer's zeal spring from the fight-instinct used in the right way. As James, Cannon, and others have pointed out, the way to end war may be to employ man's instinct of pugnacity in fighting the universal enemies of the race--fire, flood, famine, disease, and the various social evils--rather than let it spend its force in war between nations. Even our sports may be offshoots of the fight-instinct, for McDougall holds that the play-tendency has its root in the instinct of rivalry, a modified form of pugnacity. Evidently fighting-blood is a useful inheritance, even to-day, and rightly directed is a necessary part of a complete and forceful personality. This, then, completes the list of self-preservative instincts, those which are commonly called egoistic and which have been given us for the maintenance of our own individual personal lives. But our endowment includes another set of impulses which are no less important and which must be reckoned with if human conduct is to be understood. CHAPTER IV _In which we learn more about ourselves_ THE STORY OF THE INSTINCTS (Continued) II. THE RACE-PRESERVATIVE INSTINCTS