As already pointed out in Chapters VII. and VIII. the chief concussion effects on the nervous tissue of the brain and spinal cord are of a destructive nature, far exceeding those accompanying the injuries designated by the same term seen in the ordinary accidents met with in civil practice, and this damage is comparatively localised in extent. In the case of the peripheral nerves I have still employed the terms 'concussion' and 'contusion' to designate certain groups of symptoms and clinical phenomena, but any sharp distinction between the two conditions on a morbid anatomical basis is impossible. The results of severe vibratory concussion may, in fact, be more generally destructive than those of contusion, and the subsequent effects more prolonged. A certain length of the affected nerve is apparently completely destroyed as a conductor of impulses, the connective-tissue element alone remaining intact. Under these circumstances a nerve, the subject of the most serious degree of vibratory concussion, which, if cut down upon, may exhibit no macroscopic change, may take a longer period to recover than one in which the presence of considerable local thickening points to direct contact with the bullet, with resulting haemorrhage into the nerve sheath and perhaps partial gross rupture of nerve fibres. The therapeutic and prognostic importance of the above remarks, if correct, is obvious. The course of the nerve is preserved by its intact connective-tissue framework, and ultimate recovery by a regeneration of the nerve fibres is more likely to be complete, and will be just as rapid, if nature be relied on and the nerve be left untouched by the hand of the surgeon. It is, I think, undeniable that nerve trunks may escape severe or irrecoverable injury by lateral displacement. The mere fact that the trunk itself may be perforated by a slit in its long axis would suggest the possibility of displacement of the whole structure, and this no doubt occurred with some frequency. Displacement would naturally be most frequent in the case of nerves, such as those of the arm, which run long courses in comparatively loose tissue. In a remarkable case already narrated, an exploratory operation showed the musculo-spiral nerve in the upper part of the arm to have been driven into a loop which projected into, and provisionally closed, an opening in the brachial artery.