THOEACIC NEEVES. 713 



forearm it is called the dorsal interosseous nerve, and is placed in the proximal part 

 of its course beneath the superficial extensor muscles, and upon the supinator and 

 abductor pollicis longus, along with the dorsal interosseous artery. In the distal 

 half of the forearm it passes under cover of the extensor pollicis longus, and lies 

 upon the interosseous membrane. At the wrist it passes deep to the extensor 

 tendons, on to the back of the carpus, where it terminates in a gangliform enlarge- 

 ment of small size, from which branches pass to the inter-carpal articulations. The 

 nerve supplies the following branches : 



(1) Terminal articular branches to the carpal joints. 



(2) Muscular branches, in its course through the forearm. Thus, on the lateral 

 side of the radius, it supplies the extensor carpi radialis brevis and the supinator 

 muscles before it enters the fibres of the last-named muscle. After emerging from 

 the supinator it supplies a large bundle of nerves which enter the extensor 

 digitorum communis, extensor digiti quinti proprius, and extensor carpi ulnaris, near 

 their origins. At a more distal level the nerve gives off branches to^ the abductor 

 pollicis longus, extensor pollicis longus and extensor pollicis brevis, and extensor 

 indicis proprius. 



NERVI SUBSCAPULARES. 



There are two subscapular nerves (Figs. 614 and 616). 



The first or short subscapular nerve is generally double, and there may be 

 three trunks present. It arises from the posterior cord of the plexus behind the 

 axillary nerve, and comes from the fifth and sixth cervical nerves. It passes 

 distally behind the axillary artery and enters the subscapularis muscle. 



The second or lower subscapular nerve also arises behind the axillary nerve 

 from the posterior cord of the plexus (from the fifth and sixth cervical nerves). 

 Its origin is distal and lateral to that of the first nerve. It courses distally 

 behind the axillary artery and the axillary and radial nerves, to the teres 

 major muscle. It supplies branches to the lateral part of the subscapularis 

 muscle and ends in the teres major. 



NERVUS THORACODORSALIS. 



The thoraco-dorsal nerve (O.T. long subscapular) arises from the back of the 

 posterior cord of the plexus, behind the radial nerve, and from the sixth, seventh, 

 and eighth cervical nerves, or from the seventh and eighth nerves only. It is 

 directed distally and laterally between the two preceding nerves, behind the axillary 

 artery and over the posterior wall of the axilla, in company with the subscapular 

 artery, to the latissimus dorsi muscle, which it supplies on its anterior (deep) 

 surface. 



NEEVI THOEACALES. 



The anterior rami of the thoracic nerves are twelve in number, each nerve 

 emerging below the corresponding vertebra and rib. Eleven of the series are 

 intercostal, the twelfth lying below the last rib. The first, second, third, and 

 twelfth nerves present peculiarities in their course and distribution. The other 

 thoracic nerves, as already stated, are simple, and may be regarded as types 

 both in course and distribution. 



The anterior ramus of the first thoracic nerve is the largest of the series. 

 It emerges from the vertebral canal below the neck of the first rib, and divides 

 in the first intercostal space into two very unequal, superior and inferior, parts. 

 The superior and larger part ascends obliquely over the neck of the first rib, lying 

 lateral to the arteria intercostalis suprema, and enters the neck behind the sub- 

 clavian artery and the pleura. It proceeds laterally upon the scalenus 

 medius muscle and enters into the formation of the brachial plexus, as already 

 described. 



The inferior, intercostal part of the nerve is much smaller in size. It courses 



