=Shock.=—When a bone is shattered, a cavity penetrated, an important viscus wounded, a limb carried away by a round shot, pain is not so prominent a symptom as the general perturbation and alarm which supervene on the injury. This is generally described as the “shock” of a gunshot wound. The patient trembles and totters, is pale, complains of being faint, perhaps vomits. His features express anxiety and distress. This emotion is in great measure instinctive; it is witnessed in the horse hit mortally in action, no less than in his rider; it is sympathy of the whole frame with a part subjected to serious injury, expressed through the nervous system. Examples seem to show that it may occasionally be overpowered for a time, even in most severe injuries, by mental and nervous action of another kind; but this can rarely happen when the injury is a vital one. Panic may lead to similar results when the wound is of a less serious nature. A soldier, having his thoughts carried away from himself—his whole frame stimulated to the utmost height of excitement by the continued scenes and circumstances of the fight—when he feels himself wounded, is suddenly recalled to a sense of personal danger; and if he be seized with doubt whether his wound is mortal, depression as low as his excitement was high may immediately follow. This will happen according to individual character and intelligence, state of health, and other circumstances. For while, on the one hand, numerous examples occur in every action of men walking to the field hospital for assistance almost unsupported, and with comparatively little signs of distress, after the loss of an arm or other such severe injury; on the other, men whose wounds are slight in proportion are quite overcome, and require to be carried. As a general rule, however, the graver the injury, the greater and more persistent is the amount of “shock.” A rifle–bullet which splits up a long bone into many longitudinal fragments, inflicts a very much more serious injury than the ordinary fracture effected by the ball from a smooth–bore musket, and the constitutional shock bears like proportion. When a portion of one or of both lower extremities is carried away by a cannon–ball, the higher toward the trunk the injury is inflicted, the greater the shock, independent of the loss of blood. Some writers, in accounting for “shock,” lay stress on the concussion, and general mechanical effects on the whole body, of the momentum of the iron shot.[4] To a certain extent this may be true, but, judging from analogy in physics, the greater the velocity, and consequently the momentum, of a ball carrying away a limb, the less would the concussion of the trunk and distal parts of the body be. A pistol–ball at full speed will take a circular portion out of a pane of glass without disturbing the remainder; if the speed be much slackened, as when fired from a distance, it will shake the whole pane to pieces.