When the nerve is divided at the wrist, the adjacent tendons are also frequently severed.  If divided below the point at which its dorsal branch is given off, the sensory paralysis is much less marked, and the injury is therefore liable to be overlooked until the wasting of muscles and typical main en griffe ensue.  The loss of sensibility after division of the nerve before the dorsal branch is given off resembles that after division at the elbow, except that in uncomplicated cases deep sensibility is usually retained.  If the tendons are divided as well, however, deep touch is also lost.

Care must be taken in all these injuries to prevent deformity; a splint must be worn, at least during the night, until the muscles regain their power of voluntary movement, and then exercises should be instituted.

#Dislocation of the ulnar nerve# at the elbow results from sudden and violent flexion of the joint, the muscular effort causing stretching or laceration of the fascia that holds the nerve in its groove; it is predisposed to if the groove is shallow as a result of imperfect development of the medial condyle of the humerus, and by cubitus valgus.

The nerve slips forward, and may be felt lying on the medial aspect of the condyle.  It may retain this position, or it may slip backwards and forwards with the movements of the arm.  The symptoms at the time of the displacement are some disability at the elbow, and pain and tingling along the nerve, which are exaggerated by movement and by pressure.  The symptoms may subside altogether, or a neuritis may develop, with severe pain shooting up the nerve.

The dislocated nerve is easily replaced, but is difficult to retain in position.  In recent cases the arm may be placed in the extended position with a pad over the condyle, care being taken to avoid pressure on the nerve.  Failing relief, it is better to make a bed for the nerve by dividing the deep fascia behind the medial condyle and to stitch the edges of the fascia over the nerve.  This operation has been successful in all the recorded cases.

#The Sciatic Nerve.#—­When this nerve is compressed, as by sitting on a fence, there is tingling and powerlessness in the limb as a whole, known as “sleeping” of the limb, but these phenomena are evanescent. Injuries to the great sciatic nerve are rare except in war.  Partial division is more common than complete, and it is noteworthy that the fibres destined for the peroneal nerve are more often and more severely injured than those for the tibial (internal popliteal).  After complete division, all the muscles of the leg are paralysed; if the section is in the upper part of the thigh, the hamstrings are also paralysed.  The limb is at first quite powerless, but the patient usually recovers sufficiently to be able to walk with a little support, and although the hamstrings are paralysed the knee can be flexed by the sartorius and gracilis.  The chief feature is drop-foot.  There is also loss of sensation below the knee except along the course of the long saphenous nerve on the medial side of the leg and foot.  Sensibility to deep touch is only lost over a comparatively small area on the dorsum of the foot.