{illust. caption = FIG. 19--THE BROAD JUMP. Note the similarity of the expression to the facial expression of fear and of anger (Figs. 12 and 21). (Wm. J. Brownlow, drawn from photo.) tions of the leading organs that do not participate in that struggle-- the non-combatants, so to speak. Fear arose from injury, and is one of the oldest and surely the strongest emotion. By the slow process of vast empiricism nature has evolved the wonderful defensive motor me-chanism of many animals and of man. The stimulation of this mechanism leading to a physical struggle is action, and the stimulation of this mechanism without action is emotion. We may say, therefore, that fear is a PHYLOGENETIC FIGHT OR FLIGHT (Fig. 18). On this hypothesis all the organs and parts {illust. caption = FIG. 20.-FINISH OF RELAY RACE. Compare the facial expression of the runners with those in Figs. 12, 19, 22. These pictures illustrate the fact that the same mechanism is stimulated in emotion as in physical action. (Photo by Underwood and Underwood, N. Y.)} of the body are integrated, connected, or correlated for the self-preservation of the individual by the activity of his motor mechanism (Figs. 12, 19, and 20). We fear not in our hearts alone, not in our brains alone, not in our viscera alone--fear influences every organ and tissue; each organ or tissue is stimulated or inhibited according to its use or hindrance in the physical struggle for existence. By thus concentrating all or most of the nerve force on the nerve-muscular mechanism for defense, a greater physical power is developed. Hence it is that under the stimulus of fear animals are able to perform preternatural feats of strength. For the same reason, the exhaustion following fear will be increased as the powerful stimulus of fear drains the cup of nervous energy even though no visible action may result. An animal under the stimulus of fear may be likened to an automobile with the clutch thrown out but whose engine is racing at full speed. The gasoline is being consumed, the machinery is being worn, but the machine as a whole does not move, though the power of its engine may cause it to tremble.