THE ANTERIOR LIMB. 207 
(h) The serratus anterior. Origin in two portions: 
Cervical portion: Transverse processes of the posterior five 
cervical vertebrae and the anterior two ribs. 
Thoracic portion: Third to ninth ribs by separate slips 
alternating with those of the external oblique. 
Common insertion: Medial surface of the vertebral border 
of the scapula. 
The transverse artery of the neck (a. transversa colli) lies on the 
medial side of the cervical portion. 
2. Muscles arising from the axial skeleton and the pectoral 
girdle and inserted on the humerus, for the most part at its proximal 
extremity. 
(a) 
(b) 
Note the axillary lymph glands lying in the fat of the axillary 
fossa. 
The latissimus dorsi. Origin: Lumbodorsal fascia and 
four posterior ribs. Insertion: Deltoid tuberosity. A 
long flat triangular muscle, covering a considerable 
portion of the lateral surface of the thorax; having 
its dorsal angle covered by the thoracic portion of 
the trapezius. Its insertion end passes to the medial side 
of the humerus. 
The pectoralis primus (p. tenuis). Origin: Manubrium 
sterni. Insertion: Deltoid tuberosity. 
A branch of the thoracoacromial artery appears between this 
muscle and the deltoideus. 
The muscle should be raised from the surface and divided. 
The pectoralis secundus (p. major). Origin: Entire 
lateral portion of the sternum. Insertion: Anteromedial 
surface of the humerus, beginning below the head, and 
extending to the boundary between the middle and 
distal thirds. The anterior fibres are covered by those 
of (b). Some of the posterior fibres are inserted highest 
on the humerus. 
By working backward from the clavicle the muscle can be detached 
from those underneath and divided. 
