166 VETERINARY SURGICAL OPERATIONS 



the two dorsal spinal' nerves, from the plexus of which it is 

 an important component part. It accompanies the. humeral 

 artery along the arm to the internal aspect of the humero- 

 radial articulation. Descending from this point it. first, be- 

 comes very superficial on traversing the level of the in- 

 ternal radial tuberosity, but soon turns rather sharply in an 

 outward direction to take its place behind the radius in com- 

 pany with the posterior radial artery and vein. From a 

 point one inch below the radial tuberosity it is quite deeply- 

 imbedded between the radius anteriorly and the flexor 

 muscles posteriorly, which position it maintains to the level 

 of the carpal sheath, where a large branch- is given off to 

 join the ulnar in forming the external plantar nerve, while 

 the main trunk continues on the inner aspect of the leg as 

 the internal plantar nerve. In the region of the arm it gives 

 off a large branch — the antibrachial nerve, which, after sup- 

 plying the surrounding muscles, passes down the anterior 

 aspect of the leg, losing itself in the skin and antibrachial 

 fascia as far down as the carpus. At the level of the elbow 

 a large branch is supplied to the flexor muscles of the 

 phalanges, passing backward to an obtuse angle from the 

 trunk to reach the fleshy portion of these muscles. 



In the region of the arm the medium nerve is a mixed 

 one, its branches furnishing both motor and sensory impres- 

 sions to the adjacent structures, but after passing the elbow, 

 and probably at some small distance above, it contains only 

 sensory fibres. The antibrachial branch proceeding from 

 the region of the arm is mixed, but is chiefly concerned in 

 furnishing sensation to the skin and fascia of the fore arm. 

 The branch to the flexor muscles of the phalanges is largely 

 sensory, as its division leaves no depreciation of the motion 

 of the muscles. Its most interesting and important be- 

 havior occurs at the carpus, where it contributes to the for- 

 mation of both plantars, a small part only going to the 

 ulnar to form the external plantar, the major portion contin- 

 uing in its downward course as the internal plantar. The 

 median nerve, therefore, contributes to the innervation of 

 the external aspect of the leg and foot below the carpus, as 

 well as furnishing all of the sensation to the internal aspect. 

 When divided at the elbow, sensibility is banished. from the 

 internal portion of all of the structures from the lower third 

 of the metacarpus to the sole of the foot with absolute regu- 

 larity. The tendons, the bones and the skin of the middle 

 and upper thirds of the metacarpus are only partly unnerved 

 —a certain part of their sensibility is retained. On the ex- 



