36 Anatomy Applied to Medicine and Surgery. 



and in addition it produces movement of the clavicle at 

 the sterno-clavicular joint. It consists of two fan-shaped 

 portions the upper with its apex forward at the ist and 

 2nd ribs and its base attached to the upper angle and 

 vertebral border of the scapula the lower with its base 

 forward connected with the ribs from the 2nd to the 8th and 

 its apex attached to the inferior angle. We have seen 

 that the deltoid can extend the arm, but it cannot 

 raise it beyond a right angle with the body, any 

 further elevation of the arm must be done (i) by rotation 

 of the scapula at the acromio-clavicular articulation, (2) by 

 circumduction of the clavicle at the sterno-clavicular 

 articulation and (3) by elevation of the humerus by means 

 of the crossed fibres of the pect. major. These move- 

 ments of rotation and circumduction are brought about 

 partly by the lower fibres of the trapezius but chiefly by 

 the action of the serratus magnus, and especially by its 

 lower fibres which draw forward and upward the lower 

 angle of the scapula. The serratus magnus assists the 

 deltoid in raising the arm in another manner, viz., by 

 steadying the scapula, thus giving the humerus a base 

 from which to act. Paralysis of the serrati muscles pre- 

 vents the above actions, and by allowing the inferior 

 angles of the scapulae to project, produces a condition 

 known as "angel- wing" deformity. 



Base of the axilla. The skin covering the base of the 

 axilla is pigmented and has numerous sebaceous and 

 some tubular glands which give in some people a disa- 

 greeable odor. The latter are rudimentary and for this 

 reason it is possible for malignant disease to start in them. 

 Beneath the integument which is supplied by the inter- 

 costo-humeral nerve and by some of the lateral cutaneous 

 branches of the intercostals, is the superficial fascia in 

 which, when present, the superficial external mammary 



