'.•s ANATOMY IN A NUTSHELL. 



The axillary artery is divided into three parts by the Pectoralis minor 

 muscle, the part above the muscle is called the first part, the part behind it is 

 called the second part, and the part below it is called the third part. A branch 

 from the outer cord joins one from the inner cord to make the median nerve. 

 The outer cord gives off the external anterior thoracic and the musculo-cutane- 

 ous nerves. 'The inner cord gives off the ulnar, internal cutaneous, lesser in- 

 ternal cutaneous, and the internal anterior thoracic nerves. The posterior 

 cord gives off the three subscapular and divides into the circumflex and musculo- 

 spinal nerves. The musculo-spiral divides into the radial and posterior inter- 

 i isseous. 



This plexus is situated in the posterior triangle of the neck between the 

 Scalenus anticus and the Scalenus medius, being covered by the skin. Platysma 

 myoides, and deep fascia; the posterior belly of the Omo-hyoid and the trans- 

 \ ersalis colli artery cross it. It next lies above and to the outer side of thesub- 

 clavian artery: it passes behind the clavicle in the axilla where it first lies to the 

 outer side of the first portion of the axillary artery, then its cords lie externally. 

 internally, and posteriorly to the second part of the axillary artery. From the 

 third part branches are given to the upper extremity. 



The clavicle divides the brachial plexus into branches above it and branches 

 below it. The branches above are communicating, muscular, posterior thor- 

 acic, and suprascapular. 



The communicating branches are. (1) one from the fifth cervical or from 

 the loop between the fifth and sixth cervical to the phrenic, which union takes 

 place on the Scalenus anticus muscle. (2) A sympathetic connection. 



The muscular branchesare, (1 I those to the Longus colli whichcome from 

 the fifth, sixth, seventh, and eighth cervical before they enter into the brachial 

 plexus. (2) Those to the Scaleni which also come from the fifth, sixth, seventh, 

 and eighth cervical before they enter into the brachial plexus. (3) Those to 

 the Rhomboidei, which come from the fifth cervical and pass through the 

 Scalenus medius beneath the Levator anguli scapulae, which it sometimessup- 

 plies, to tiie Rhomboidei. (4) The nerve to the Subclavius which comes from 

 the fifth and sometimes the sixth cervical. It often communicates with the 

 phrenic. 



The posterior thoracic of long thoracic (external respiratory of Hell) comes 

 from the fifth, sixth, and seventh cervical. It is formed in the substance of the 

 Scalenus medius, then passes behind the brachial plexus and axillary artery to 

 supply the digitations of the Serratus magnus. 



The suprascapular i- formed by the fifth and sixth: it passe> beneath the 

 Trapezius and Omo-hyoid to pass through the suprascapular notch into the 

 supraspinous fossa where ii gives two branches to the Supraspinatus muscle 

 and a branch to the shoulder-joint, then passes around the greal scapular notch 

 into the infraspinous fossa, giving two branches to the Infraspinatus muscle 

 and one to the scapula itself. 



All the other branches are below the clavicle. 



The external or superficial anterior thoracic nerve comes from the outer 

 cord jusl below the clavicle and it- fibers may he traced to the fifth, sixth, and 



