460 



THE MUSCLES AND FA8CLJE 



A Sternalis muscle is occasionally found in the pectoral region; it may be confined to one 

 side, or may be bilateral. It is sometimes represented by delicate scattered fibres overlying a 

 normal Pectoralis major, or by a well-developed muscle associated with a defective Pectoralis 

 major. It is often attached to the sternal end of the Sternomastoid; below, it becomes lost in 

 the presternal fascia or in the aponeurosis of the External oblique. This variant is regarded 

 as a displaced and rotated segment of the Pectoralis major; it is supplied by branches from the 

 anterior thoracic nerve. 



Dissection. Detach the Pectoralis major by dividing the muscle along its attachment to 

 the clavicle, and by making a vertical incision through its substance a little external to its line of 

 attachment to the sternum and costal cartilages. The muscle should then be reflected outward, 

 and its tendon carefully examined. The Pectoralis minor is now exposed, and immediately 

 above it, in the interval between its upper border and the clavicle, a strong fascia, the costd- 

 coracoid membrane. 



FIG. 349. Muscles of the thorax and front of the arm, showing some of the boundaries of the axilla 



The Costocoracoid Membrane, or the Clavipectoral Fascia (fascia coraco- 

 clavicularis), is a strong fascia, situated under cover of the clavicular portion of 

 the Pectoralis major muscle. It occupies the interval between the Pectoralis 

 minor and Subclavius muscle, and protects the axillary vessels and nerves. Traced 

 upward, it splits to enclose the Subclavius muscle, and its two layers are attached 

 to the clavicle, one in front of and the other behind the muscle; the deep layer fuses 

 with the deep cervical fascia and with the sheath of the axillary vessels. Mesally, 

 it blends with the fascia covering the first two intercostal spaces, and is attached 

 also to the first rib internal to the origin of the Suho-iavius muscle. Lateral///, 

 it is very thick and dense, and is attached to the coracoid process. The portion 



