of the formation of adhesions when the tendon passes through muscle than through interosseous membrane.  The palmaris longus is anastomosed with the abductor pollicis longus (extensor ossis metacarpi pollicis), thus securing a fair amount of abduction of the thumb.  The flexor carpi ulnaris may also be anastomosed with the common extensor of the fingers.  The extensors of the wrist may be shortened, so as to place the hand in the position of dorsal flexion, and thus improve the attitude and grasp of the hand.

The superficial branch of the radial (radial nerve) and the deep branch (posterior interosseous), apart from suffering in lesions of the radial, are liable to be contused or torn is dislocation of the head of the radius, and in fracture of the neck of the bone.  The deep branch may be divided as it passes through the supinator in operations on old fractures and dislocations in the region of the elbow.  Division of the superficial branch in the upper two-thirds of the forearm produces no loss of sensibility; division in the lower third after the nerve has become associated with branches from the musculo-cutaneous is followed by a loss of sensibility on the radial side of the hand and thumb.  Wounds on the dorsal surface of the wrist and forearm are often followed by loss of sensibility over a larger area, because the musculo-cutaneous nerve is divided as well, and some of the fibres of the lower lateral cutaneous branch of the radial.

[Illustration:  FIG. 91.—­To illustrate the Loss of Sensation produced by Division of the Median Nerve.  The area of complete cutaneous insensibility is shaded black.  The parts insensitive to light touch and to intermediate degrees of temperature are enclosed within the dotted line.

(After Head and Sherren.)]

#The Median Nerve# is most frequently injured in wounds made by broken glass in the region of the wrist.  It may also be injured in fractures of the lower end of the humerus, in fractures of both bones of the forearm, and as a result of pressure by splints.  After division at the elbow, there is impairment of mobility which affects the thumb, and to a less extent the index finger:  the terminal phalanx of the thumb cannot be flexed owing to the paralysis of the flexor pollicis longus, and the index can only be flexed at its metacarpo-phalangeal joint by the interosseous muscles attached to it.  Pronation of the forearm is feeble, and is completed by the weight of the hand.  After division at the wrist, the abductor-opponens group of muscles and the two lateral lumbricals only are affected; the abduction of the thumb can be feebly imitated by the short extensor and the long abductor (ext. ossis metacarpi pollicis), while opposition may be simulated by contraction of the long flexor and the short abductor of the thumb; the paralysis of the two medial lumbricals produces no symptoms that can be recognised.  It is important to remember that when the median nerve is divided at