436 



MYOLOGY 



in the interval between it and the Latissimus dorsi, where it closes in the axillary 

 space and forms the axillary fascia ; it divides at the lateral margin of the Latis- 

 simus dorsi into two layers, one of which passes in front of, and the other behind 

 it; these proceed as far as the spinous processes of the thoracic vertebrae, to which 

 they are attached . As the fascia leaves the lower edge of the Pectoralis major to cross 

 the floor of the axilla it sends a layer upward under cover of the muscle; this lamina 

 splits to envelop the Pectoralis minor, at the upper edge of which it is continuous 

 with the coracoclavicular fascia. The hollow of the armpit, seen when the arm 

 is abducted, is produced mainly by the traction of this fascia on the axillary floor, 

 and hence the lamina is sometimes named the suspensory ligament of the axilla. 

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

 continuous with the fibrous sheaths of the Recti abdominis. 



Fio. 410. Superficial muscles of the chest and front of the arm. 



The Pectoralis major (Fig. 410) is a thick, fan-shaped muscle, situated at the 

 upper and forepart of the chest. It arises 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 ; from the 



