THE BREAST AND AXILLA 31 



of the pectoralis minor and breaks up into deltoid (p. 35), 

 acromial (p. 10), clavicular (p. 9), and pectoral branches. The 

 pectoral branches pass downwards in the interval between 

 the two pectoral muscles, accompanied by branches of the 

 lateral anterior thoracic nerve. In excision of the breast, 

 haemorrhage may be reduced by securing these branches prior 

 to removal of the sternal portion of the pectoralis major. They 

 may be hooked up on the forefinger through the interval between 

 the clavicular and sternal portions of the pectoralis major 

 (p. 3), as they wind round the upper border of the pectoralis 

 minor (Stiles). 



The Lateral (Long) Thoracic Artery passes from the 

 second part of the axillary artery downwards and medially, 

 along the lower border of the pectoralis minor, to the fifth 

 intercostal space. Its External Mammary branch reaches the 

 mamma by passing medially over the pectoralis major. 



The pectoral and infra-clavicular lymph glands, with their 

 efferent lymph vessels from the upper and lateral parts of 

 the pectoral plexus, are so intimately connected with the 

 pectoral fascia of the anterior axillary wall that this wall is 

 usually removed in malignant disease of the breast. The costo- 

 sternal portion of the pectoralis major is divided near its insertion 

 and is then reflected from its origin. As the cut muscle is 

 drawn forwards and laterally, the fascia covering the serratus 

 anterior and the external oblique is rendered tense, and may 

 be removed as a wide sheet as far back as the subscapularis. 

 It is at this stage of the operation that the long thoracic nerve 

 (of Bell) is in danger, as it runs down the medial wall of the 

 axilla between the serratus anterior and its covering fascia. 



The Medial Wall of the Axilla is formed by the upper 

 five ribs and external intercostal muscles, partially covered by 

 the upper digitations of the serratus anterior. 



The Serratus Anterior (S. magnus) arises from the lateral 

 surfaces of the upper eight ribs, a short distance in front of the 

 mid-axillary line. Its fibres pass backwards, closely applied 

 to the chest wall, and are inserted into the ventral aspect of the 

 vertebral border of the scapula. It receives its nerve-supply 

 from the long thoracic nerve (of Bell) (C. 5, 6, 7) (pp. 97, 131). 

 The serratus anterior pulls the scapula forwards, and, when 

 opposed by the rhomboids, it steadies the scapula in the 

 movements of forward pushing. In addition, by rotating the 

 scapula it helps to produce flexion of the upper arm beyond a 



