the wrist, deep touch can be appreciated over the whole of the area supplied by the nerve; the injury, therefore, is liable to be over looked.  If, however, the tendons are divided as well as the nerve, there is insensibility to deep touch.  The areas of epicritic and of protopathic insensibility are illustrated in Fig. 91.  The division of the nerve at the elbow, or even at the axilla, does not increase the extent of the loss of epicritic or protopathic sensibility, but usually affects deep sensibility.

[Illustration:  FIG. 92.—­To illustrate Loss of Sensation produced by complete Division of Ulnar Nerve.  Loss of all forms of cutaneous sensibility is represented by the shaded area.  The parts insensitive to light touch and to intermediate degrees of heat and cold are enclosed within the dotted line.

(Head and Sherren.)]

#The Ulnar Nerve.#—­The most common injury of this nerve is its division in transverse accidental wounds just above the wrist.  In the arm it may be contused, along with the radial, in crutch paralysis; in the region of the elbow it may be injured in fractures or dislocations, or it may be accidentally divided in the operation for excising the elbow-joint.

When it is injured at or above the elbow, there is paralysis of the flexor carpi ulnaris, the ulnar half of the flexor digitorum profundus, all the interossei, the two medial lumbricals, and the adductors of the thumb.  The hand assumes a characteristic attitude:  the index and middle fingers are extended at the metacarpo-phalangeal joints owing to paralysis of the interosseous muscles attached to them; the little and ring fingers are hyper-extended at these joints in consequence of the paralysis of the lumbricals; all the fingers are flexed at the inter-phalangeal joints, the flexion being most marked in the little and ring fingers—­claw-hand or main en griffe.  On flexing the wrist, the hand is tilted to the radial side, but the paralysis of the flexor carpi ulnaris is often compensated for by the action of the palmaris longus.  The little and ring fingers can be flexed to a slight degree by the slips of the flexor sublimis attached to them and supplied by the median nerve; flexion of the terminal phalanx of the little finger is almost impossible.  Adduction and abduction movements of the fingers are lost.  Adduction of the thumb is carried out, not by the paralysed adductor pollicis, but the movement may be simulated by the long flexor and extensor muscles of the thumb.  Epicritic sensibility is lost over the little finger, the ulnar half of the ring finger, and that part of the palm and dorsum of the hand to the ulnar side of a line drawn longitudinally through the ring finger and continued upwards.  Protopathic sensibility is lost over an area which varies in different cases.  Deep sensibility is usually lost over an area almost as extensive as that of protopathic insensibility.