COSTAL REGION. 193 



Relation. Internally with the ribs, transversalis costarum, 

 and longissimus dorsi ; externally with the rhomboideus, serratus 

 magnus, and latissimus dorsi. 



Action. Respiratory; the anterior portion drawing the ribs 

 outwards and forwards, acts as an inspiratory, the posterior, by 

 drawing them backwards and upwards as an expiratory muscle. 



TRAXSVERSALIS COSTARFM. 

 ( Trachelo-costalis. ) 



(PL in. is.) 



Situated on the supero- lateral part of the thorax, it is long, 

 thin, and semipenniform,-the fibres passing downwards, outwards, 

 and forwards, its numerous muscular bundles each terminating 

 in a flat tendon. 



Origin. From the transverse processes of the first lumbar 

 vertebrae, and the ribs near their tubercles. 



Insertion. To the external surface of all the ribs, a tendon 

 to each, and one to the last cervical vertebra. 



R'lation. Externally with the preceding muscle ; internally 

 with the ribs ; superiorly with the longissimus dorsi. 



Action. It compresses the ribs, assisting in expiration. 



LEVATOBES COSTARUM. 

 ( Transverso-costales. ) 



Situated deeply on the back, these muscles are small, flat, and 

 triangular, extending obliquely downwards and backwards. They 

 are fleshy and tendinous. 



Origin. Superiorly, from the transverse processes of the 

 dorsal vertebrae, just above the tubercles of the ribs. 



Insertion. Inferiorly to the external faces of the ribs, just 

 above their angles. 



Relation. Externally with the longissimus dorsi ; internally 

 with the external intercostals, with which posteriorly they are 

 much blended. 



Action. To raise and draw the ribs forwards, thus acting as 

 inspiratory muscles. 



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