142 SPECIAL ANATOMY. 



first rib. cartilage. Ins. : Clavicula (the external end of the in- 

 ferior surface). Use: to draw the acromial end of the clavicle 

 downwards, and press the sternal end against the sternum, on 

 which account in fracture of the clavicle the outer end projects 

 over the inner. Elevates also the first rib (m. inspiratorius), the 

 Clavicula being fixed. 

 Nerves: pectoral, anterr. 



215. 4. Serratus anticus major (costo-scapularis). 



Pos. : on the side of the thorax, covered, above, by pectoralcs, 

 below, by latissim. dorsi and the skin, behind, by subscapularis. 

 Or.: Costae 1 to 8, external surface (with nine or ten dentations). 

 Ins.: Basis scapulas (inner lip), above and below very thick; 

 united with rhomboidei and subscapular. by strong fibre-cellular 

 tissue. Use: to draw the scapula forwards and outwards; or 

 the first to the eighth ribs upwards and inwards. 



Nerves : thorarid, intercostales. 



216. 5. Intercostales externi and interni. 



Pos. : in the intercostal spaces. The fibres of the external 

 pass forwards and downwards, those of the internal backivards 

 and downwards. Or. : the inferior border of each rib. Ins. : 

 the superior border of the following inferior rib. Mm. externi 

 reach from the neck of the rib to the cartilage. Mm. interni 

 commence at the angle, terminate at the sternum. Use: both the 

 same. They approximate the ribs, either upwards in fixing the 

 first rib (by means of Mm. scaleni) inspiratio ; or downwards 

 in fixing the twelfth rib (by m. quadratus lumb.), exspiratio. 



Nerves: intercostales. 



217. 6. Infraco stales, 



variable in number and direction, lying on the internal wall of 

 the chest between ribs and diaphragm, vertical or oblique in 

 shorter or longer striae; and serving to assist the Mm. inter- 

 costales. 



218. 7. Triangularis sterni. 



Pos.: behind the sternum, before the diaphragm; separated 

 from the rib cartilages by Vasa mammaria. Or. : Corp. sterni 

 (the external border) and Proc. ensiform. Ins. : Costse, two to 

 five, together with the cartilages (the inferior border). Use: to 

 draw the second to the fifth ribs downwards. 



Nerves: intercostales. 



