AXILLARY SPACE 25 



minor and posteriorly with the fascial sheath of the axillary 

 vessels (Fig. 12). It is perforated, above the upper border 

 of the pectoralis minor, by the cephalic vein, the thoraco- 

 acromial vessels, and the lateral anterior thoracic nerve. 

 Note (i) that the fibres of the membrane run medio-laterally, 

 (2) that they are put on the stretch when the arm is abducted, 

 and (3) 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-acromialarter. ^^^^^.^ ,, , .^^ 



_ First rib 



Axillary artery 

 Axillary sheath 



Axillary fascia 



FIG. 12. 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 proximal 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 a communication is formed between the 

 medial and lateral anterior thoracic nerves, across the front of 

 the axillary artery and behind the costo-coracoid membrane. 



