forward; used in swimming. Fixed above the pectorales, 

 draw the body forward; the major does not draw up the ribs, 

 the minor does not seem to, so that they have no inspiratory 

 action. 



The subclavius depresses the clavicle or steadies it; may 

 act in inspiration; supports the sternoclavicular joint. The 

 pectoralis minor draws the coracoid down and forward, depresses 

 the shoulder, throws the lower angle of the scapula backward, 

 acts with the levator and rhomboidei in rotating the scapula. 

 The scapula is slung by the serratus magnus and rhomboidei, 

 is kept in equilibrium by them ; the lower portion of the serratus, 

 combined with the trapezius, rotates the scapula on an axis 

 near its superior angle and elevates the shoulder; the upper 

 fibers bring the scapula forward and down, assisted by the 

 pectoralis minor; the w r hole muscle brings the scapula forward, 

 acts in all movements of pushing, keeps the scapula pressed 

 to the ribs; of no importance in respiration; the middle fibers 

 only might pull .ribs down. 



THE MUSCLES OF THE THORAX 



Mm. inter costales externi, thicker behind than in front, 

 are directed obliquely downward and forward between the 

 external lips of the borders of two ribs; they extend from the 

 tuberosities to the outer ends of the cartilages, not quite reach- 

 ing them above, but continued along their borders in the lower 

 two spaces. They are continued to the sternum as anterior 

 intercostal aponeuroses or ligamenta intercostalia externa. 



Mm. intercostalcs interni, thicker in front, incline down and 

 back, but less obliquely than the external set; are attached to 

 the ridge on the inner surfaces of the upper rib and to the 

 internal lip of the upper border of the lower rib to which it 

 is attached. Anteriorly they reach the sternum, and the 

 last two are continuous with the internal oblique muscle; 

 posteriorly they go to the angles or a little beyond. Their 

 deficiency behind is supplied by the posterior intercostal apon- 

 euroses, which merge on one side into the anterior costo- 

 transversalis ligament, and on the other into a thin fascia 

 between the muscles. 



Mm. infracostales (subcostales) consist of muscular and 

 aponeurotic fibers, which are attached to the inner surface 



