58o 



HUMAN ANATOMY. 



Fig 



the sternal fibres of the pectoraHs major and by all the muscles passing from the 

 trunk to the humerus and scapula. It is rotated on a vertical axis so that its inner 

 end points backward and its outer end forward. The cause of the rotation is the 

 action of the two pectorals upon the shoulder and the contraction of the serratus, 

 which ( the support of the clavicle having been removed) draws the scapula (and 

 with it the point of the shoulder) inward and forward instead of more directly for- 

 ward, and so causes an anterior projection of the acromial end of the outer 

 fragment. 



Theoretically the inner fragment is displaced upward by the clavicular fibres of 

 the sterno-mastoid, but this action is so strongly resisted by the costo-clavicular 

 (rhomboid) ligament and by the upper and inner fibres of the pectoralis major, as 

 well as by the subclavius, that it is not often productive of much deformity (Fig. 563). 

 The rationale of the good effect of recumbency with the head slightly elevated 

 is evident. The weight of the upper extremity ceases to drag the outer fragment 

 downward. The vertebral border of the scapula is pressed closely to the thorax 

 by the weight of the trunk. Its outer border, therefore, cannot be drawn forward by 

 the pectorals and serratus, but tends to fall backward and outward, correcting both 



the rotation and the inward 

 displacement. The slight ele- 

 vation of the head relaxes the 

 sterno-cleido-mastoid and re-, 

 moves whatever influence it 

 may have in raising the outer 

 end of the inner fragment. 



Fractures within the limits 

 of the rhomboid ligament at 

 the inner end or within those 

 of the conoid and trapezoid 

 ligaments at the outer end are 

 attended by but little displace- 

 ment. 



Fi-adures of the scapula 



have already been dealt with 



(page 254). Muscular action 



influences them but little be- 



yondwhat has been mentioned. 



The fascia beneath and 



connected with the clavicle is 



of much surgical importance. 



The superficial fascia of the 



thorax splits to enclose the breast. The processes which pass from it to the skin 



(Cooper's " ligamenta suspensoria" ), by their involvement and contraction in 



carcinoma, produce the characteristic adhesion and dimpling of the skin. 



The deep pectoral fascia splits to form the sheath of the pectoralis major muscie. 

 Carcinoma of the mamma will usually be found adherent to this layer on the anterior 

 surface of the muscle. Such adhesion can best be demonstrated by attempting to 

 move the tumor and breast in the direction of the pectoral fibres. Motion trans- 

 verse to that line may, even in cases in which the tumor and muscle are inseparably 

 connected, appear to be free, because the muscle itself is moved on the subjacent 

 structures. 



Beneath the deep pectoral fascia an additional sheet, the clavi-pectoral fascia, 

 extends as a continuation downward of the sheath of the subclavius, the two layers 

 of which begin above at the two lips of the subclavian groove on the inferior surface 

 of the clavicle and unite into one layer at the lower edge of the subclavius. This 

 layer is continuous towards the sternum with the deep fascia covering in the first and 

 second intercostal spaces ; externally it is attached to the coracoid process ; inferiorly, 

 after splitting to enclose the pectoralis minor muscle, it blends with the axillary fascia. 

 The portion of the clavi-pectoral fascia above the upper border of the pectoralis 

 minor is known as the costo-coracoid membrane. It, together with the subclavius 



Subclavius 



Dissection of fracture of middle of clavicle. 



