294 



MUSCLES AND FASCIAE. 



FASCIA OF THE THOEAX. 



The superficial fascia of the thoracic region is a loose cellulo-fibrous layer, con- 

 tinuous with the superficial fascia of the neck and upper extremity above, and 

 of the abdomen below. Opposite the mamma, it subdivides into two layers, one 



of which passes in front, the other 

 iBseotum of Upper Extremrty. 



/. Dissection of 



PECTORAL REGION 



and AXILLA 



of these layers numerous septa pass 

 into its substance, supporting its 

 various lobes; from the anterior 

 layer, fibrous processes pass for- 

 ward to the integument and nipple, 

 inclosing in their areolse masses of 

 fat. These processes were called, 

 by Sir A. Cooper, the ligamenta 

 suspensoria, from the support they 

 afford to the gland in this situation. 

 On removing the superficial fascia, 

 the deep fascia of the thoracic region 

 is exposed ; it is a thin aponeurotic 

 lamina, covering the surface of the 

 great Pectoral muscle, and sending 

 numerous prolongations between 

 its fasciculi. It is attached, in the 

 middle line, to the front of the 

 sternum, and, above, to the clavi- 

 cle ; it is very thin over the upper 

 part of the muscle, somewhat thicker 

 in the interval between the Pecto- 

 ralis major and Latissimus dorsi, 

 where it closes in the axillary space, 

 and divides at the margin of the 

 latter muscle into two layers, one 

 of which passes in front, and the 

 other behind it; these proceed as 



far as the spinous processes of the dorsal vertebras, to which they are attached. 



At the lower part of the thoracic region, this fascia is well developed, and is con- 



tinuous with the fibrous sheath of the Eecti muscles. 



PALM 0fHANO 



ANTEEIOR THORACIC KEGION. 



Pectoralis Major. 



Pectoralis Minor. 



Subclavius. 



The Pectoralis Major (fig. 169) is a broad, thick, triangular muscle, situated at 

 the upper and fore part of the chest, in front of the axilla. It arises from the 

 sternal half of the clavicle, its anterior surface, and from one half the breadth of 

 the front of the sternum, as low down as the attachment of the cartilage of the 

 sixth or seventh rib ; its origin consisting of aponeurotic fibres, which intersect 

 those of the opposite muscle. It also arises from the cartilages of all the true 

 ribs, and from the aponeurosis of the External oblique muscle of the abdomen. 

 The fibres from this extensive origin converge towards its insertion, giving to the 

 muscle a radiated appearance. Those fibres which arise from the clavicle pass 

 obliquely downwards and outwards, and are usually separated from the rest by a cel- 

 lular interval ; those from the lower part of the sternum and the cartilages of the lower 

 true ribs pass upwards and outwards, whilst the middle fibres pass horizontally. 

 As these three sets of fibres converge, they are so disposed that the upper overlap 



