AXILLARY SPACE 15 



immediately below their attachment to the clavicle, and turn them distally 

 towards their insertion. Whilst doing this secure the branches of 

 the lateral anterior thoracic nerve as they pass into the muscle. Under 

 cover of the clavicular part of the pectoralis major follow the cephalic vein 

 and the deltoid branch of the thoraco-acromial artery medially and secure 

 the acromial and pectoral branches of the latter artery. Clean these 

 vessels, and directly below the clavicle display the costo-coracoid membrane, 

 and, more inferiorly and laterally, the fascia on the proximal and lateral part 

 of the pectoralis minor. Cut through the sternocostal part of the pectoralis 

 major about two inches from the lateral border of the sternum. Turn the 

 medial part towards the medial plane, verifying its attachment to the costal 

 cartilages and to the sternum and to the aponeurosis of the external oblique 

 muscle of the abdomen. Turn the lateral part of the muscle towards the 

 arm ; whilst doing this secure the medial anterior thoracic nerve which 

 perforates the pectoralis minor and ends in the pectoralis major. Examine 

 the insertion of the pectoralis major. Note that the tendon of insertion 

 consists of two laminae which are united together below ; in other words, 

 the tendon is folded on itself and between the two laminae a tmicous bursa 

 is frequently interposed. The clavicular fibres and the upper sternocostal 

 fibres are attached to the anterior lamina ; the lower sternocostal fibres 

 to the posterior lamina. Both lamina: are attached to the lateral lip of 

 the intertubercular sulcus of the humerus, but the deep lamina ascends 

 to a higher level, and it becomes continuous above with a layer of 

 fascia which is attached to the small tubercle of the humerus. The 

 inferior border of the tendon of insertion is continuous with the deep fascia 

 of the arm. 



When the pectoralis major is completely reflected a continuous sheet ot 

 fascia is exposed, which extends from the clavicle superiorly to the axillary 

 fascia inferiorly and from the wall of the thorax medially to the arm laterally ; 

 this is the so-called davipectoral fascia or suspensory ligament of the axilla. 

 It is because of the attachment of this fascial sheet to the clavicle 

 superiorly and to the axillary fascia inferiorly that the floor of the axilla is 

 raised when the clavicle is elevated as the arm is abducted from the side. 

 The pectoralis minor muscle, passing obliquely from its origin on the 

 thoracic wall to its insertion into the coracoid process of the scapula, runs 

 through the substance of the clavipectoral fascia and divides it into three 

 parts : (i) the part above the muscle, (2) the part which encloses the muscle, 

 and (3) the part below the muscle. The uppermost part is the costocoracoid 

 membrane, the intermediate part is the sheath of the pectoralis minor. No 

 special term is applied to the lowest part, but it should be noted that it lies 

 posterior to the lower part of the pectoralis major, and that it covers the 

 lower portions of the axillary vessels and nerves. 



Membrana Costocoracoidea (Costo-coracoid Membrane). 



The costo-coracoid membrane occupies the gap between the 

 clavicle above and the pectoralis minor below. It extends 

 from the first rib medially to the coracoid process laterally, 

 and from the clavicle above to the pectoralis minor below. 

 Its upper part is split into two layers, an anterior and a 

 posterior, which are attached to the corresponding borders of 

 the clavicle. Enclosed between them is the subclavius muscle. 

 The strongest part of the membrane is that which extends 

 along the lower border of the subclavius, from the first rib to 



