THE ANTERIOR THORACIC REGION 



457 



site the mamma it divides into two layers, one of which passes in front, the other 

 behind that gland; and from both of these layers numerous septa pass into its 

 substance, supporting its various lobes; from the anterior layer fibrous processes 

 pass forward to the integument and nipple. These processes were called by Sir 

 A. Cooper the suspensory ligaments (ligamenta suspensoria), from the support 

 they afford to the gland in this situation. 



The deep thoracic fascia 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 mid-line, to the front of the sternum, and above 

 to the clavicle; externally and below it becomes continuous with the fascia over 

 the shoulder, axilla, and thorax. It is very thin over the upper part of the muscle, 

 thicker in the interval between the Pectoralis major and Latissimus dorsi, where 

 it closes in the axillary space, and 

 is known as the axillary fascia (fas- 

 cia axillaris). It passes behind 

 into the fascia of the Latissimus 

 dorsi and Teres major, in front 

 into the fascia of the Deltoid and 

 outward into the fascia of the arm. 

 The fascia of the Latissimus dorsi 

 divides at the outer margin of the 

 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 thora- 

 cic vertebrae, to which they are 

 attached. As the axillary fascia 

 leaves the lower edge of the Pecto- 

 ralis major to pass across the floor 

 of the axilla it sends a layer up- 

 ward under cover to the muscle, 

 the deep pectoral fascia; this lamina 

 splits to envelop the Pectoralis 



3. Dissection of 

 Shoulder and Arm. 



1. Dissection of 

 Pectoral Region 

 and Axilla. 



Bend of Elbow. 



4, Forearm. 



5. Palm of Hand. 



FIG. 346. Dissection of the upper extremity. 



minor, at the upper edge of which 

 it becomes continuous with the 

 costocoracoid membrane (_clavi pec- 

 toral fascia). The hollow of the 

 axilla, seen when the arm is ab- 

 ducted, is mainly produced by the 

 traction of this fascia on the 

 axillary floor, the axillary fascia, 

 hence it is sometimes named the suspensory ligament of the axilla. The axillary 

 fascia is not a distinct and complete rigid floor of the axillary space. Like all 

 other fasciae, it follows muscular planes, and splits to encompass vessels, nerves, 

 and muscles. In it are numerous perforations. At the lower part of the thoracic 

 region the deep thoracic fascia is well developed, and is continuous with the 

 fibrous sheath of the Recti abdominis. 



The Pectoralis major (m. pectoralis major) (Fig. 347) is a broad, thick, triangular 

 muscle, situated at the upper and fore part of the thorax, in front of the axilla. 

 Itjimea from the anterior surface of the sternal half of the clavicle; from half the 

 breadth of the anterior surface of the sternum, as low down as the attachment 

 of the cartilage of the sixth or seventh rib; this portion of its origin consists of 

 aponeurotic fibres, which intersect with those of the opposite muscle; it also arises 

 from jhe cartilages of all true ribs, with the exception, frequently, of the first 



