1 6 THE UPPER EXTREMITY 



the coracoid process ; this portion is frequently called the 

 costo-coracoid ligament. The membrane is continuous below 

 with the fascial sheath of the pectoralis minor and posteriorly 

 with the fascial sheath of the axillary vessels. It is perforated, 

 above the upper border of the pectoralis minor, by the cephalic 

 vein, the thoraco-acromial artery, and the lateral anterior 

 thoracic nerve. Note that the fibres of the membrane run 

 medio-laterally, that they are put on the stretch when the 

 arm is abducted, and that they are relaxed when the arm is 

 by the side. The surgeon takes advantage of these facts 

 when he is ligaturing the first part of the axillary artery. 



Clavicle ,/ 



Subclavius 



Thoraco-acromial artery 



"Y. First rib 



Costo-coracoid 

 membrane 



Axillary artery 

 Axillary sheath 



-Axillary fascia 

 F IG . 7 . Diagram of the Costo-coracoid Membrane. 



Dissection. Cut through the anterior layer of the upper part of the 

 costo-coracoid membrane and expose the subclavius muscle. Pass the 

 handle of a knife below the lower border of the subclavius and upwards 

 behind the muscle and demonstrate the posterior layer of the upper part 

 of the membrane. Clear away the remains of the membrane and follow 

 the cephalic vein to its junction with the axillary vein, the thoraco-acromial 

 artery to the axillary trunk, and the lateral anterior thoracic nerve to the 

 lateral cord of the brachial plexus. Clean the upper parts of the axillary 

 artery and vein and the lateral cord of the brachial plexus. Note that 

 the axillary vein lies to the medial side of the artery on a somewhat 

 anterior plane, and that as the arm is abducted from the side the vein 

 passes more and more in front of the artery. The lateral cord of the 

 plexus lies to the lateral side of the artery and on a posterior plane. 

 Behind the upper border of the pectoralis minor find the medial anterior 

 thoracic nerve, and note that an anastomosis is formed between the medial 

 and lateral anterior thoracic nerve across the front of the artery and behind 

 the costo-coracoid membrane. 



