Other emotional states however, besides fear, arise and require suppression. The tendency to feel sympathetic pain or distress at harrowing sights and sounds, disgust or nausea at the happenings in the trenches, the “jumpy” tension in face of unknown dangers such as mines—all these, like fear, are or have been biologically useful under natural conditions and, like it, are deeply and innately rooted in man. But the unnatural conditions of modern warfare make it necessary that they shall be held in check for extraordinarily long periods of time. The impossibility of regarding modern methods of warfare in the same light as natural and primitive means of fighting appears very clearly when we consider the instinctive and emotional factors involved in the two sets of circumstances. In natural fighting, face to face with his antagonist, and armed only with his hands or with some primitive weapon for close fighting, the uppermost instinct in a healthy man would naturally be that of pugnacity, with its accompanying emotion of anger. The effect of every blow would be visible, and the intense excitement aroused in the relatively short contest would tend to obliterate the action of other instincts such as that of flight, with its emotion of fear. But in trench warfare the conditions are different. A man has seldom a personal enemy whom he can see and upon whom he can observe the effects of his attacks. His anger cannot be directed intensely night and day against a trench full of unseen men in the same way in which it can be provoked by an attack upon him by an individual. And frequently the assaults made upon him nowadays are impersonal, undiscriminating and unpredictable, as in the case of heavy shelling. One natural way is forbidden him in which he might give vent to his pent-up emotion, by rushing out and charging the enemy. He is thus attacked from within and without. The noise of the bursting shells, the premonitory sounds of approaching missiles during exciting periods of waiting, and the sight of those injured in his vicinity whom he cannot help, all assail him, while at the same time he may be fighting desperately with himself. Finally, he may collapse when a shell bursts near him, though he need not necessarily have been injured by actual contact with particles of the bursting missile, earth thrown up by its impact, or gases emanating from its explosion. He may or may not be rendered unconscious at the time.[11] He is removed from the trenches with loss of consciousness or in a dazed or delirious condition with twitchings, tremblings or absence of muscular power.